General Anatomy PDF - 4Med Stds

General Anatomy By: Yared Asmare (BSc, MSc, Ass’t Prof.) UoG, CMHS, Dept of Human Anatomy Yared Asmare(Asst Prof.) 1  Pre-clerkship I Module title: Introduction to medicine Module code: INMD - 2011 Course name: Anatomy Course duration: 5 weeks...

General Anatomy By: Yared Asmare (BSc, MSc, Ass’t Prof.) UoG, CMHS, Dept of Human Anatomy Yared Asmare(Asst Prof.) 1  Pre-clerkship I Module title: Introduction to medicine Module code: INMD - 2011 Course name: Anatomy Course duration: 5 weeks Yared Asmare(Asst Prof.) 2  Objective Describe the nature and organization of the major systems of the human body Yared Asmare(Asst Prof.) 3  Teaching and learning methods Interactive lecture Assignment Discussion Demonstration/Practice e.g. Video show, Dissection, Histology lab. Group discussion Yared Asmare(Asst Prof.) 4  Educational Resources Basic sciences lab (Histology and DR) Anatomical charts and mannequins Histological slides or specimens Yared Asmare(Asst Prof.) 5  HISTORY OF ANATOMY “The past is not dead history, it is living material out of which man builds for the future”. Rene Dubos (1901-1982) Yared Asmare(Asst Prof.) 6  References Printed Materials (Textbooks, Handouts, Anatomy atlases ) Text Books Drake RL.,Vogl W., and Mitchell AW. Gray’s anatomy for students. latest edition. Keith L. Moore, T.V.N. Persaud and Mark G Turchia. “The developing human. Clinically oriented embryology”. latest edition. Elaine N. Marieb: Human Anatomy , latest ed. Gerard J, Tortora. Introduction to the human body. latest edition. Snell, Richard S. Clinical neuroanatomy. latest edition. Van De Graaff: Human Anatomy. latest Edition Kent. Human Anatomy. Latest edition Keith L. Moore: Clinically Oriented Anatomy. latest edition Yared Asmare(Asst Prof.) 7 … Learners Guide  Handout  Text books  E- books Learning facilities/Infrastructures  Classroom  Histology lab.  Dissection room Yared Asmare(Asst Prof.) 8  Methods of assessment Progressive assessment (Total module courses)  40% Written progress assessment/tests - 15% Clinical skill lab - 5% Basic science lab - 15% Hospital visit - 5% Final Assessment (Total module courses)  60% Written - 40% OSCE/OSPE - 20% Yared Asmare(Asst Prof.) 9 Introduction to Anatomy (34hrs) Definition of Anatomy and historical background ⃙ Subdivisions of Anatomy ⃙ Approaches to studying Anatomy ⃙ Levels of Structural Complexity of the body ⃙ Body Planes and Sections ⃙ Axes of the body ⃙ Movement of the body ⃙ Body Cavities ⃙Overview of each system ⃙Integumentary system Yared Asmare(Asst Prof.) 10 Home take assignment 1. Historical background of Anatomy? 2. Why to learn/study Anatomy? Yared Asmare(Asst Prof.) 11  DEFINITION OF ANATOMY  The word “Anatomy” is derived from the Greek term “Anatome” consisting of two words Ana up/apart and Tome cutting. Therefore Anatomy means to cut apart, divide or dissect  Anatomy is the study of the structure of the human body its parts. oIt is also called morphology, the science of form. oAn old and proud science that has been a field of serious intellectual investigation for at least 2300 years. oIt was the most prestigious biological discipline of the 1800s and is still dynamic. Therefore: ∴ Anatomy is a branch of science that deals with structure of the body and their relation. Yared Asmare(Asst Prof.) 13  … o If you are preparing for a career in the health sciences, your knowledge of human anatomy is the foundation of your clinical practice. o Anatomy is closely related to physiology. o Anatomy and physiology are studied in separate courses, but they are truly inseparable, because structure supports function.  For example, the lens of the eye is transparent and curved; it could not perform its function of focusing light if it were opaque and uncurved.  Similarly, the thick, long bones in our legs could not support our weight if they were soft and thin. Yared Asmare(Asst Prof.) 14  Subdivisions of the Anatomy  Gross anatomy: is the study of body structures that can be examined by the naked eye.  Microscopic anatomy: is the study of structures that are so small and can be seen only with a microscope. Cells and cell parts, and tissues A knowledge of microscopic anatomy is important because physiological and disease processes occur at the cellular level. Yared Asmare(Asst Prof.) 15  Subdivision …  Regional or Topographic anatomy: is the study of all structures in a single body region, such as the abdomen or head, are examined as a group.  Applied anatomy: the practical application of anatomical knowledge to the diagnosis and treatment of diseases.  Ultrastructural anatomy: the ultramicroscopic study of structures too small to be seen with a light microscope. Yared Asmare(Asst Prof.) 16  Subdivision … Developmental anatomy: traces the structural changes that occur in the body throughout the life span and the effects of aging. Explore how body structures form, grow, and mature. ©Embryology: is the study of how body structures form and develop before birth. © knowledge of embryology helps you understand the complex design of the adult human body and helps to explain birth defects, which are anatomical abnormalities that occur during embryonic development and are evident after birth. Yared Asmare(Asst Prof.) 17  Subdivision …  Pathological anatomy: deals with the structural changes in cells, tissues, and organs caused by disease. Briefly, it is the study of structural changes caused by diseases. used primarily for medical diagnosis and scientific research.  Radiographic anatomy: is the study of internal body structures by means of X-ray studies and other imaging techniques. Yared Asmare(Asst Prof.) 18  Subdivision … Comparative anatomy: is the study of similarities and differences in the anatomy of different species.  It is closely related to evolutionary biology and phylogeny (the evolution of species). Surface anatomy: is the study of shapes and markings (called landmarks) on the surface of the body that reveal the underlying organs. ⃙It deals with anatomical features that can be studied by sight, without dissection. ⃙Some have everyday names like the palm of the hand, the sole of the foot, and the nape of the neck. ⃙Used to identify the muscles that bulge beneath the skin in weight lifters, and clinicians use it to locate blood vessels for placing catheters, feeling pulses, and drawing blood. Yared Asmare(Asst Prof.) 19  APPROACHES TO STUDY ANATOMY I. Systemic approach In systemic approach all the organs with related functions are studied together. Classification is based on function (structures that have a common function studied together)  about 11 systems are found in human body. E.g. Circulatory, Respiratory, Integumentary, Skeletal, … II. Regional approach Deals with several systems located in a particular region of the body. all structures in a single body region, such as the abdomen or head, are examined as a group. E.g. Limb (Upper & Lower) Back, Abdomen, Head, Neck … Used mostly in dissection room and useful to physicians and surgeons.  Regional anatomy focuses on specific external and internal regions of the body and how different systems work together in that region.  Systemic anatomy focuses on the anatomy of different organ systems, such as the respiratory or nervous system. Yared Asmare(Asst Prof.) 20 Yared Asmare(Asst Prof.) 21 LEVELS OF STRUCTURAL ORGANIZATION OF HUMAN BODY  Life processes of the human body are maintained at several levels of structural organization.  These include the chemical, cellular, tissue, organ, organ system, and the organism level The human body has many levels of structural complexity. I. Chemical level Includes all atoms and molecules essential for maintaining life. oMajor atoms : C, H, O, N, Ca, K & Na oMolecules: proteins, carbohydrates, fats, nucleic acids (DNA, RNA) & vitamins. Atoms unite to form molecules; molecules are building blocks of the structures at cellular level. II. Cellular level Cells are the smallest living things in the body. Cells are the basic structural and functional unit of an organism. Cells have 2 or 3 principal parts/partition/compartments oPlasma (cell) membrane oCytoplasm Yared Asmare(Asst Prof.) 22 oNucleus Yared Asmare(Asst Prof.) 23  Organization… III. Tissue level Tissues are groups of similar cells (and the substance surrounding them) that usually arise from common ancestor cells and work together to perform a particular function. 4 basic types of tissues: Epithelial, Muscle, Connective & Nervous. IV. Organ level Organs are structures that are composed of three or more different tissues that have specific functions and usually have recognizable shape. V. System level A system consists of several related organs that have a common function. e.g. Digestive system - breakdown of food and absorption. VI. Organismic level: is the result of all of the simpler levels working in union to sustain life. Yared Asmare(Asst Prof.) 24 Level of organization Yared Asmare(Asst Prof.) 25  … At the lowest level of organization (chemical) Histochemistry & Cytochemistry.  At the cellular level  Cytology.  At the tissue level  Histology.  At the organic level  Organology.  At the systemic level  Systemic Anatomy.  At the organismic level  Gross anatomy For example: o Cell  Osteocytes  Muscle fibres o Tissue  Osseous tissue  Muscular tissue o Organ  Bone  Muscle o Systemic  Skeletal System  Muscular System Yared Asmare(Asst Prof.) 26 ANATOMICAL POSITION  Anatomical position is standard, common, visual reference position of a body universally used in anatomical descriptions.  Used to describe body parts & their location.  It is the position of reference for anatomical nomenclature.  Explained as follows Body stands erect in upright position facing the observer Feet flat on the floor together/far apart with shoulder level Head level and the eyes facing directly forward. Arms placed at the sides, The palms of the hands turned forward and The thumbs pointed away from the body.  Additionally the term right and left always refer to those sides belonging to the person or cadaver being viewed  not to the right and left sides of the viewer. Yared Asmare(Asst Prof.) 27 Yared Asmare(Asst Prof.) 28 Anatomical Terminology  terms of position & relation  Most anatomical terms are based on ancient Greek or Latin words. ⃙For example, the arm is the brachium and the thigh bone is the femur.  Standard directional terms are used by medical personnel and anatomists to explain precisely where one body structure lies in relation to another.  Directional terms indicate the relationship of one part of the body to another.  Anatomical terminology is less wordy and confusing.  Most often used are the paired terms superior/inferior, anterior/ventral, posterior/dorsal, medial/lateral, and superficial/deep… Yared Asmare(Asst Prof.) 29  Term of position and relation. I. Superior  above. I. Lateral  to the side. II. Inferior  below. II. Median  at the median III. Cranial (rostral, cephalic)  plane. nearer to the head. III. Proximal  upper. IV. Caudal  nearer to the tail IV. Distal  lower. V. Anterior  in front. V. Palmar  on the side of VI. Posterior  behind. the palm of the hand. VII. Ventral  in the direction of the VI. Plantar  on the side of abdomen. the sole of the foot. VIII. Dorsal  in the direction of the VII. Superficial  nearer to back. the body surface. IX. Medial  nearer to the midline. VIII.Deep  nearer to the center of the body. Yared Asmare(Asst Prof.) 30 Yared Asmare(Asst Prof.) 31 Yared Asmare(Asst Prof.) 32 Yared Asmare(Asst Prof.) 33 Yared Asmare(Asst Prof.) 34  BODY PLANES AND SECTIONS  Planes are imaginary flat surfaces that are used to divide the body or organs to visualize interior structures.  The body is divided by the following planes (imaginary flat surfaces) in different sections. 1. Sagittal Plane  A vertical plane that divides the body or an organ into right and left sides. Midsagittal (median)plane: o If the plane passes through the midline of the body or organ and divides it into equal right and left sides. Parasagittal plane: o If the sagittal plane does not pass through the midline but instead divides the body or an organ into unequal right and left sides. Yared Asmare(Asst Prof.) 35  Body plane… 2. Frontal (coronal) plane Divides the body or an organ into anterior (front) and posterior (back) portions. 3. Transverse (cross-sectional or horizontal) plane Divides the body or organ into superior (top) and inferior (bottom) portions. The above planes are all at right angles to one another. 4. Oblique plane Passes through the body or organ at an angle between the transverse plane and vertical plane. When we cut organs through these planes the resulting flat surfaces is termed as section.  E.g. transverse plane gives transverse section. Yared Asmare(Asst Prof.) 36 Planes and sections Yared Asmare(Asst Prof.) 37 Planes and sections Yared Asmare(Asst Prof.) 38 Planes and Sections of lower limb… Yared Asmare(Asst Prof.) 39 Planes and Sections of brain… Yared Asmare(Asst Prof.) 40 Axes of movements:  The movements of the body are based on three main axes, which are perpendicular to each other. 1. Longitudinal or vertical axis: runs from the center of the head to the sole of the foot in longitudinal direction. It is perpendicular to the floor. Medial or internal rotation Movements Lateral or external rotation Pronation Supination 2. Sagittal axis: runs from anterior to posterior aspect of the body or vice versa. It is parallel to the floor. Movements Abduction Yared Asmare(Asst Prof.) 41 Adduction 3. Transverse or horizontal axis: runs from right to left or from left to right. It is parallel to the floor. Movements Flexion Extension Circumduction: is a movement to take place on all the three axes. Yared Asmare(Asst Prof.) 42  Concept of the movements 1. Flexion: indicates bending or decreasing the angle b/n the bones or part of the body. 2. Extension: indicates straightening or increasing the angle between the bones or part of the body. 3. Abduction: means moving away from the median plane (upper and lower limbs). o In the fingers is moving the other finger away from the 3rd digit or middle finger. o Moving the other toes away from the 2nd toe. 4. Adduction: means moving toward the median plane (upper and lower limbs). o In finger moving the other finger toward the median plane of the hand (3rd finger). o Moving the other toes toward the 2nd toe. Yared Asmare(Asst Prof.) 43 5. Medial / internal rotation: brings the anterior surface of the limb closer to the median plane. 6. Lateral / external rotation: takes the anterior surface of the limb away from the median plane. 7. Circumduction: is the circular movement that is a combination of flexion, abduction, extension and adduction and the end of the limb describe the circle. 8. Opposition: is the movement by which the pad of the 1st digit (thumb) is brought to another digit pad. 9. Protrusion: is the anterior (forward) movement as occurs in the protruding the mandible (sticking the chin out). Yared Asmare(Asst Prof.) 44 10. Retrusion: is the posterior (backward) movement as occurs in retruding the mandible (tucking the chin in) 11. Protraction and retraction: is the anteriorly and posteriorly movement of the shoulder. 12. Eversion: moves the sole of the foot away from the median plane (turning the sole laterally). 13. Inversion: moves the sole of the foot toward the median plane (facing the sole medially). 14. Pronation: is the movement of the forearm and hand that rotates the radius medially around its longitudinal axis. So that the palm of the hand faces posteriorly and its dorsum faces anteriorly. 15. Supination: is the movement of the forearm and hand that rotates the radius laterally around its longitudinal axis.  So that the dorsum of the hand faces posteriorly and the palm faces anteriorly. Yared Asmare(Asst Prof.) 45 Yared Asmare(Asst Prof.) 46 Yared Asmare(Asst Prof.) 47 Yared Asmare(Asst Prof.) 48  Body cavities & membranes ⃙ A body cavity: is any space or compartment, or potential space, in an animal body. help protect, separate, and support internal organs. Bones, muscles, ligaments, and other structures separate the various body cavities from one another.  Body membranes are thin sheets/layers of cells or tissues which cover the surface of internal organs, the outside of the body and lines various body cavities.  A membrane is a thin, pliable tissue that covers, lines, partitions, or connects structures. Cutaneous /dry membrane e.g. skin  Mucous membrane: GIT mucosa  Serous membrane: pleura, pericardium & peritoneum Yared Asmare(Asst Prof.) 49 Yared Asmare(Asst Prof.) 50 Yared Asmare(Asst Prof.) 51  …  For general clinical descriptions, clinicians use four quadrants of the abdominal cavity: right upper, right lower, left upper, and left lower.  The four quadrants are defined by two planes: Transumbilical plane: passing through the umbilicus and IV disc between the L3 and the L4 vertebrae. Median plane: passing longitudinally through the body, dividing it into right and left halves. Yared Asmare(Asst Prof.) 52 Abdominal regions and quadrants Median plane Trans umbilical plane Yared Asmare(Asst Prof.) 53 The nine regions are delineated by four planes:  Two horizontal: Subcostal plane: passing through the inferior border of the 10th costal cartilage on each side. Transtubercular plane: passing through the iliac tubercles and the body of the L5 vertebra.  Two vertical: Midclavicular planes: passing from the midpoints of clavicles to the midinguinal points, the midpoints of lines joining the anterior superior iliac spines and the superior edge of the pubic symphysis. Yared Asmare(Asst Prof.) 54  …  Clinicians subdivide the abdominal cavity into nine regions to locate abdominal organs or pain sites: Midclavicular planes Subcostal plane Transtubercular plane Yared Asmare(Asst Prof.) 55 … Yared Asmare(Asst Prof.) 56 Yared Asmare(Asst Prof.) 57 Yared Asmare(Asst Prof.) 58 GENERAL ANATOMY OF THE OF SKELETAL SYSTEM (OSTEOLOGY). Yared Asmare(Asst Prof.) 59 …  Without bones, you could not survive. oYou would be unable to perform movements such as walking or grasping, and oThe slightest blow to your head or chest could damage your brain or heart.  The skeletal system forms the framework of the body. √ if you are familiarity with the names, shapes, & positions of individual bones it will help you locate and name many other anatomical features. Yared Asmare(Asst Prof.) 60  Skeletal system…  Osteology is the part of anatomy devoted to the study of the bone  its formation, form, structure and functions.  The word Skeleton comes from the Greek word meaning “Dried up Body”.  The skeleton accounts for about 18-20 % of our body weight.  It consists of bones, cartilages, joints and ligaments.  Each individual bone is an organ.  Locomotory system: is formed by bones, joints and muscles. Bones and cartilages are passive parts and muscles and joints are active parts of the locomotory system. Yared Asmare(Asst Prof.) 61  Function of the skeletal system. 1. Formation of the supportive framework and permanent shape of the body. 2. Protection of some soft and delicate organs. A. Bones of the head protect the brain and the sensory organ. B. Bones of the thoracic wall protect intrathoracic organs like the lungs, the heart and great vessels. C. Bones of the vertebral column protect the spinal cord. D. Pelvic bones protect some organs of the genitourinary system and Gastro Intestinal tract (GIT). 3. Movement. 4. Storage of minerals and fat. 5. Production of blood cells. 6. To provide an attachment site for muscles and act as rigid lever to move the body and its parts. Yared Asmare(Asst Prof.) 62  Classification of bones  Bones are classified by their shape rather than size as long, short, flat and irregular.  Is based in the three dimension of the space (length, width and thickness)). I. Long bones: cylindrical & are considerably longer than they wide. E.g. The bones of the arms, legs, hands, and feet (but not the wrists and ankles). II. Short bones: are roughly cubed shaped. E.g. The bones of the wrists and ankles. III. Flat Bones: they are longer and wider than thicker (thin, flattened and usually somewhat curved).  Forming by an inner and outer thin lamina of compact bone (inner and outer lamellar) between which lies a spongy substance. e.g. bones of the skull (diploe), scapula, hip bone and ribs. IV. Irregular Bones: they have various shapes that do not fit into any of the above categories.  They have similar structure to short bones. E.g. bones of the vertebral column. Yared Asmare(Asst Prof.) 63 Yared Asmare(Asst Prof.) 64. 1. Sesamoid bone:  usually have a shape similar to a sesame seed.  They are situated at the end of long bones of the limbs. E.g. patella or knee cap  helps the tendons to glide over the bony surfaces and prevent excessive wear and tear.  they act alter the direction of pull of the tendons. 2. Pneumatic Bones:  they contain air filled cavities lined with mucous membrane. e.g. maxilla, frontal, ethmoid and sphenoid bones. Yared Asmare(Asst Prof.) 65  … 2. Wormian or sutural bones:  small fragments of bones between bones of the skull. 3. Heterotopic bones:  are the abnormal calcifications in soft tissues.  Short, flat, and irregular bones are all made of spongy bone covered with a thin layer of compact bone. Yared Asmare(Asst Prof.) 66  Structures of typical long bone  With few exception, all bones in the body have the same general structure. I. Diaphysis: also called shaft, forms the long axis of a long bone/the shaft or long main cylindrical portion II. Epiphysis: end of a long bone III. Metaphyses: are the areas between the epiphysis and diaphysis and include the epiphyseal plate in growing bones. IV. Articular cartilage: over joint surfaces acts as friction reducer & shock absorber V. Medullary cavity: marrow cavity Yared Asmare(Asst Prof.) 67  Membrane Endosteum:  lining of marrow cavity and central canals of osteons  is osteogenic  bone producing  containing bone depositing cells and bone destroying cells. Periosteum:  tough membrane covering bone but not the articular cartilage  Richly supplied by nerves and blood vessels  Secured to the underlying by perforating fibers sharpey’s fiber Fibrous layer  dense irregular CT Osteogenic layer  bone cells Yared Asmare(Asst Prof.) 68 Structures of typical long bone Yared Asmare(Asst Prof.) 69  Bone tissue  Consists of widely separated cells surrounded by large amounts of extracellular matrix.  Has both organic and inorganic components.  Chemical Composition o Healthy bone is half as strong as steel in resisting compression and equally strong in resisting tension.  Bone is composed of the following: o 35% organic components cells, fibers, and ground substance o The organic substance particularly collagen, contribute the flexibility and tensile strength that allow bone resists stretching and twisting. o 65% inorganic components minerals, mostly calcium phosphate and calcium carbonate o Provides bones hardness o Bone is not completely solid since it has small spaces for vessels and bone marrow Spongy bone has many such spaces Compact bone has very few such spaces Yared Asmare(Asst Prof.) 70  Classification of the Bones According to their Location. A) Axial Skeleton:  This is located around the longitudinal axis of the body.  i.e. most of the bones of the axial skeleton constituted the central body core of the body, the axis.  This group is composed of 80 Bones B) Appendicular Skeleton:  This is composed of bones found in the limbs and their corresponding girdles forming a total of 126 bones. Yared Asmare(Asst Prof.) 71 Based on gross observation bone has two different structures: Compact bone  Dense outer layer that looks smooth and solid to the naked eye.  outer layer provides strength.  Makes up the shaft of long bones and the external layer of all bones  Resists stresses produced by weight and movement Spongy (cancellous)  consists of trabeculae (a honeycomb of small needle like), containing marrow for blood cell production or fat storage.  It forms most of the structure of short, flat, and irregular bones, and the epiphyses of long bones.  Spongy bone tissue is light and supports and protects the bone marrow. Yared Asmare(Asst Prof.) 72 Yared Asmare(Asst Prof.) 73  According to their microscopic appearances. 1. Non - lamellar, Immature or Woven Bones: The term woven denotes that it has a network of randomly oriented large collagen fibres in its matrix. 2. Lamellar Bones: All mature bones are Lamellar. According to their developmental origin. 1. Membranous (mesenchymal, dermal). 2. Cartilaginous (Chondral). Yared Asmare(Asst Prof.) 74  Blood and Nerve Supply of Bone  Nutrient arteries: enter through nutrient foramen supplies compact bone of diaphysis & red marrow  Metaphyseal a: supply the metaphysis and are a branch from the nutrient artery  Periosteal arteries: supply periosteum and are branches of Nutrient and epiphyseal aa  Epiphyseal aa.: supply red marrow & bone tissue of epiphyses Yared Asmare(Asst Prof.) 75  Innervations of bones Blood vessels of bones are accompanied by many nerve fibers most of which are vasomotor.  Some sensory fibers are also end in the periosteum and adventitia of blood vessels. Some of these sensory fibers to the periosteum are pain fibers, due to which the periosteum is specially sensitive to tearing and tension. The vasomotor nerves serve for constriction and dilation of the blood vessels. Yared Asmare(Asst Prof.) 76 Yared Asmare(Asst Prof.) 77  BONE FORMATION  All embryonic connective tissue begins as mesenchyme.  Bone formation is termed osteogenesis or ossification and begins when mesenchymal cells provide the template for subsequent ossification. Prior to week 8 Embryonic skeleton is comprised of hyaline cartilage and fibrous membranes Week 8 and beyond Bone tissue begins to develop Majority of fibrous or cartilaginous structures eventually replaced with bone Intramembranous Fibrous membrane ossification Membrane bone Endochondral Hyaline cartilage ossification Cartilage bone Yared Asmare(Asst Prof.) 78 Embryonic Skeleton Yared Asmare(Asst Prof.) 79 Intramembranous ossification Forms the flat bones of the skull, the mandible and clavicle. An ossification center forms from mesenchymal cells, they convert to osteoblasts and lay down osteoid matrix. The matrix surrounds the cell and then calcifies as the osteoblast becomes an osteocyte. The calcifying matrix centers join to form bridges of trabeculae that constitute spongy bone with red marrow in between. On the periphery the mesenchyme condenses and develops into the periosteum Yared Asmare(Asst Prof.) 80 Intramembranous ossification Yared Asmare(Asst Prof.) 81  Endochondral ossification  Involves replacement of cartilage by bone and form most of the bones of the body.  The first step in endochondral ossification is the development of the cartilage model. I. Development of Cartilage model  Mesenchymal cells form a cartilage model of the bone during development.  Growth of cartilage model in length by chondrocyte cell division and matrix formation (interstitial growth) in width by formation of new matrix on the periphery by new chondroblasts from the perichondrium (appositional growth)  Cells in mid region burst and change pH triggering calcification and chondrocyte death Yared Asmare(Asst Prof.) 82 Endochondral ossification Yared Asmare(Asst Prof.) 83 Endochondral ossification Yared Asmare(Asst Prof.) 84  Endochondral ossification… 2. Development of Primary Ossification Center Perichondrium lays down periosteal bone collar Nutrient artery penetrates center of cartilage model Periosteal bud brings nutrient artery and vein and osteoblasts and osteoclasts to center of cartilage model Osteoblasts deposit bone matrix over calcified cartilage forming spongy bone trabeculae Osteoclasts form medullary cavity 3. Development of Secondary Ossification Center Blood vessels enter the epiphyses around time of birth Spongy bone is formed but no medullary cavity 4. Formation of Articular Cartilage Cartilage on ends of bone remains as articular cartilage.85 Yared Asmare(Asst Prof.)  BONE GROWTH Growth in Length  Bone grows in length occurs at the epiphyseal or growth plate  The activity of the epiphyseal plate is the only means by which the diaphysis can increase in length.  When the epiphyseal plate closes, is replaced by bone, the epiphyseal line appears and indicates the bone has completed its growth in length. Epiphyseal plate or cartilage growth plate  Cartilage cells are produced by mitosis on epiphyseal side of plate  Cartilage cells are destroyed and replaced by bone on diaphyseal side of plate  Between ages 18 to 25, epiphyseal plates close.  Cartilage cells stop dividing and bone replaces the cartilage (epiphyseal line)  Growth in length stops at age 25 Yared Asmare(Asst Prof.) 86  Zones of Growth in Epiphyseal Plate I. Zone of resting cartilage  anchors growth plate to bone II. Zone of proliferating cartilage  rapid cell division (stacked coins) III. Zone of hypertrophic cartilage  cells enlarged & remain in columns IV. Zone of calcified cartilage  thin zone, cells mostly dead since matrix calcified  Osteoclasts removing matrix  Osteoblasts & capillaries move in to create bone over calcified cartilage V. Ossification zone is a region of transformation from cartilage tissue to bone tissue. Yared Asmare(Asst Prof.) 87 Yared Asmare(Asst Prof.) 88  Growth in Thickness Bone can grow in thickness or diameter only by appositional growth Two processes Osteoblasts beneath periosteum secrete bone matrix onto external bone surface Osteoclasts on endosteal surface remove bone Yared Asmare(Asst Prof.) 89  Bone Remodeling Bones are not inert structures within the human body; they continue to change over the course of a lifespan Remodeling: o is the ongoing replacement of old bone tissue by new bone tissue. o involves the resorption of old or damaged bone, followed by the deposition of new bone material. o protects the structural integrity of the skeletal system and metabolically contributes to the body's balance of calcium and phosphorus. o old bone is constantly destroyed by osteoclasts, whereas new bone is constructed by osteoblasts. o continual redistribution of bone matrix along lines of mechanical stress. e.g. distal femur is fully remodeled every 4 months Yared Asmare(Asst Prof.) 90  Fracture and Repair of Bone A fracture is any break in the continuity of a bone. Healing is faster in bone than in cartilage due to lack of blood vessels in cartilage Healing of bone is still slow process due to vessel damage. Yared Asmare(Asst Prof.) 91 Yared Asmare(Asst Prof.) 92 Yared Asmare(Asst Prof.) 93 Yared Asmare(Asst Prof.) 94  Fracture repair involves I. Formation of fracture hematoma  Damaged blood vessels produce clot in 6 - 8 hours, after bone cells die  Inflammation brings in phagocytic cells for clean-up duty  New capillaries grow into damaged area II. Formation of fibrocartilagenous callus formation ~3 weeks  Fibroblasts invade the procallus & lay down collagen fibers  Chondroblasts produce fibrocartilage to span the broken ends of the bone III. Formation of bony callus  Changes to spongy bone that joins 2 broken ends of bone  Lasts 3-4 months IV. Bone remodeling o Compact bone replaces the spongy in the bony callus o Surface is remodeled back to normal shape Yared Asmare(Asst Prof.) 95 Yared Asmare(Asst Prof.) 96  Osteoporosis  is (bone porous condition) low bone mass due to deterioration and bone reabsorption is faster than bone deposition.  Fractures occur easily, especially in the vertebrae, femur, or hip.  The basic problem is that bone resorption (breakdown) outpaces bone deposition (formation).  In large part this is due to depletion of calcium from the body—more calcium is lost in urine, feces, and sweat than is absorbed from the diet.  Bone mass becomes so depleted that bones fracture, often spontaneously, under the mechanical stresses of everyday living.  For example, a hip fracture might result from simply sitting down too quickly.  Osteoporosis primarily affects middle-aged and elderly people, 80% of them women. Yared Asmare(Asst Prof.) 97  Osteoporosis  Older women suffer from osteoporosis more often than men for two reasons: I. Women’s bones are less massive than men’s bones II. production of estrogens in women declines dramatically at menopause, while production of the main androgen, testosterone, in older men diminishes gradually and only slightly.  Estrogens and testosterone stimulate osteoblast activity and synthesis of bone matrix.  Besides gender, risk factors for developing osteoporosis include a  family history of the disease,  European or Asian ancestry,  thin or small body build,  an inactive lifestyle,  cigarette smoking,  a diet low in calcium and vitamin D,  more than two alcoholic drinks a day, and  the use of certain medications. Yared Asmare(Asst Prof.) 98 Yared Asmare(Asst Prof.) 99 Yared Asmare(Asst Prof.) 100  Anatomy, Bone Markings Bone markings are projections and depressions found on bones. The surface features of bones vary considerably, depending on the function and location in the body. Bone markings are important to the identification of individual bones and bony pieces and aid in the understanding of functional and evolutionary anatomy. They are used by clinicians and surgeons, especially orthopedists, radiologists, forensic scientists, detectives, osteologists, and anatomists. The functionality of bone markings: ⃙ joints formation to produce movement or lock bones in place ⃙Provide structural support to muscle and connective tissue. ⃙Provide circumferential stabilization and protection to nerves, Yared Asmare(Asst Prof.) 101 vessels, and connective tissue.  Bone markings… There are three general classes of bone markings: Articulations Projections holes.  An articulation is where two bone surfaces come together to form joints.  A projection is an area of a bone that projects above the surface of the bone. Used for attachment points for tendons and ligaments. size and shape is an indication of the forces exerted through the attachment to the bone.  A hole is an opening or groove in the bone that allows blood vessels and nerves to enter the bone. size and shape reflect the size of the vessels and nerves that penetrate the bone at these points. Yared Asmare(Asst Prof.) 102  There are two Categories of bone markings. A. Projections or Processes: Which grow out from the surface of the bone provides a site for the attachment of structures like ligaments and tendons and help in the formation of joints. B. Depressions/cavities/openings: Which are indentations. Yared Asmare(Asst Prof.) 103  Projection as site of muscle attachment: Crest: a raised or prominent part of the edge of a bone.  Spine: a sharp, slender, often pointed projection.  Trochanter: a very large, blunt, irregularly shaped process. Tubercle: small round projection.  Tuberosity: a large tubercle/moderate prominence  Epicondyle: raised area on a condyle Projections that help in the formation of the Joints:  Condyle: a round projection.  Head: rounded or expanded portion carried on a narrow neck.  Facets: A smooth, flat surface that forms a joint with another flat bone or another facet Yared Asmare(Asst Prof.) 104  Depression commonly seen in bones: ⃙Fissure: a narrow, slit like opening. ⃙Foramen: opening though a bone. ⃙Fossa, Pit or Fovea: a Shallow depression in a bone. ⃙Meatus or Canal: a tube-like channel that extends within the bone, provide passage and protection to nerves, vessels, and even sound. ⃙Sinus: a depression within a bone filled with air and lined with a mucous membrane. ⃙Notch or incisures: a depression in the margin of bones. ⃙Ramus: arm like bars of bone that forms an angle with the main part of the bone. Yared Asmare(Asst Prof.) 105 Yared Asmare(Asst Prof.) 106 Yared Asmare(Asst Prof.) 107  RELATED CLINICAL TERMS  Bone graft: Transplantation of a piece of bone from one part of a person’s skeleton to another part where bone has been damaged / lost.  The graft, often taken from the crest of the iliac bone of the hip, encourages regrowth of lost bone.  Bony spur: An abnormal projection on a bone due to bone overgrowth; is common in aging bones.  Ostealgia: Pain in a bone.  Osteomyelitis ( “bone and marrow inflammation”): Bacterial infection of the bone and bone marrow.  The pathogen enters bones either from infections in surrounding tissues or through the bloodstream, or follows a compound bone fracture.  Pathologic fracture: Fracture occurring in a diseased bone and involving slight or no physical trauma.  An example is a broken hip caused by osteoporosis.  The hip breaks first, causing the person to fall. Yared Asmare(Asst Prof.) 108  Classification of bones based on their locations  206 named bones of the human skeleton are grouped in to axial and appendicular skeletons in adults.  At birth, the skeleton consists of approximately 270 bones. Axial skeleton  Forms long axis of the body  80 bones (skull, hyoid bone, auditory ossicles, vertebral column, thoracic cage) Yared Asmare(Asst Prof.) 109 Classification of the Bones According to their Location. A) Axial Skeleton: This is located around the longitudinal axis of the body that is most of the bones of the axial skeleton constituted the central body core of the body, the axis. This group is composed of 80 Bones constituted by: 1- Skull a) Cranium ---- 8 b) Face --------- 14 2- Hyoid ------------------- 1 3- Auditory Ossicles ----- 6 4-Vertebral Column ----- 26 5-Thorax a) Sternum ----1 b) Ribs ----- 24 Total 80 Yared Asmare(Asst Prof.) 110 B) Appendicular Skeleton: This is composed of bones found in the limbs and their corresponding girdles forming a total of 126 bones: 1- Shoulder Girdle a) Clavicle ----- 2 b) Scapula ----- 2 2- Upper Limb a) Humerus ------ 2 b) Ulna ---------- 2 c) Radius ------- 2 d) Carpals -------16 e) Metacarpals -10 f) Phalanges ---28 3- Pelvic Girdle Coxal, Hip, Pelvic or Innominate bones---2 4-Lower Limb a) Femur -----------2 b) Tibia ----------- 2 c) Fibula --------- 2 d) Patella ---------- 2 e) Tarsals ------- 14 f) Metatarsals ---10 g) Phalanges ----28 111 Total 126 Yared Asmare(Asst Prof.) Yared Asmare(Asst Prof.) 112  Cartilage Cartilage is a strong, flexible connective tissue that protects joints and bones. Is a semi-rigid but flexible avascular connective tissue found at various sites within the body Consists of cells (chondrocytes) in lacunae Matrix is gel like and contains collagenic and elastic fibers Has no blood vessel, it receives nutrients through diffusion Yared Asmare(Asst Prof.) 113  Types of cartilage 1. Hyaline cartilage o Firm and somewhat flexible o Matrix contains many collagenic fibers o Found at end of long bones (articular cartilage), in nose and at the ends of ribs 2. Fibrocartilage  Matrix contains wide rows of thick collageneous fibers  Able to with stand tension and pressure  Found in menisci(knee joint) and discs between vertebrae 3. Elastic cartilage  Matrix contains elastic fibers  Very flexible  Found in epiglottis and ear flaps Yared Asmare(Asst Prof.) 114 Yared Asmare(Asst Prof.) 115  Arthrology ∞ a branch of anatomy concerned with joints or articulations. ∞ the study of how bones are joined to permit (or prevent) movement. A joint or articulation: ∞ is the arrangement whereby separate bone or cartilage are attached each other or it is a place where rigid elements of the skeleton meet. ∞ is the relation of two or more bones or cartilages to one another at their region of contact. In most of the joints bones are joined to bones, but some of them join bones to cartilages, cartilages to cartilages and teeth to their bony sockets. Yared Asmare(Asst Prof.) 116  Structural Classification ∞ In the formation of a joint, the structure found b/n the adjoining ends of the bones is either a cavity or connective tissue. ∞ The cavity separates the bone ends while the connective tissue interconnects them. Therefore: ∞ The articulating ends of bones in some joints are separated by a fluid containing articular cavity which is enclosed by a synovial membrane, i.e. the ends are discontinuous which renders them a free movement. Such joints are grouped as 1. synovial joints, freely moveable joints or diarthrosis. ∞It includes the following varieties. Hinge joint Pivot joint Ball and socket joint Gliding (plane) joint Saddle joint Yared Asmare(Asst Prof.) 117  Structural classification…  Adjoining ends of articulating bones can be attached to each other by an interposed connective tissue without a remarkable separation.  In such joints the ends of the bones are said to be continuous, due to which there is little or no movement. Constituted by: I. Fibrous joints: when the tissue b/n the articulating ends of bone is a dense fibrous connective tissue. II. Cartilaginous joints: where the tissue separating the articulating ends is cartilage Yared Asmare(Asst Prof.) 118 Classification based on axes or degrees of freedom of movement o Synarthrosis (immovable) joints o Amphiarthrosis (slightly movable) joints o Diarthrosis (freely moveable) joints 1. Synarthrosis 2. Amphiarthrosis  Sutures ⃙ Symphysis  Synchondrosis ⃙ Syndesmosis  Gomphosis ⃙ Some synovial joints 3. Diarthrosis Uniaxial joints Biaxial joints Multiaxial joints The first two are mainly restricted to the axial skeleton while the third dominants in the limbs. Yared Asmare(Asst Prof.) 119  Fibrous joints Fibrous joints are classified into three types. A. Syndesmosis:  Bones are interconnected by bundles of dense collagenous or elastic connective tissue.  The fibrous connective tissue b/n the bones can be organized as an interosseous membrane or a ligament.  e.g. interosseous membranes of the forearm and the leg, ligamentum nuchae, distal tibiofibular joint.  Such joints are slightly moveable. Yared Asmare(Asst Prof.) 120 Syndesmosis Yared Asmare(Asst Prof.) 121  B. Sutures The immovably interconnected flat bones of the skull are joined by short collagen fibers trapped b/n their opposing edges. These sutures help the compression of fetal head during delivery and allow free growth of the brain. The sutures ossify after birth and the bones become fused by bony fusion or synostosis. e.g. Joints between bones of the skull. Type of Suture joints Serrate suture  saw like articulation e.g. sagittal suture Squamous suture  margin of the bone overlaps with that of articulating bone e.g. squamous suture Plane suture  margins of articulating bones are fairly smooth e.g. median palatine suture Yared Asmare(Asst Prof.) 122 Yared Asmare(Asst Prof.) 123  Fibrous joints… C. Gomphosis: This is the fixation of the teeth in their alveoli or sockets by collagenous fibers (dento-alveolar articulation) forming a synarthrotic (immoveable) joint. All the fixing ligaments around the root of a tooth form the periodontal ligament. Yared Asmare(Asst Prof.) 124 Yared Asmare(Asst Prof.) 125  Cartilaginous joints  The cartilaginous joints include transitional stages in complete bony fusion and joints which retain at least a modified cartilage throughout life.  There are two types of cartilaginous joints: A. Synchndrosis: (Primary cartilaginous joints) bones are temporarily and immovably interconnected by a hyaline cartilage until a complete bony continuity occurs. Such joints are found in the growth centers, e.g. epiphyseal plate, articulation of the first rib with the sternum… Synchondrotic joints ossify later in life usually at around the age of 25 years. Yared Asmare(Asst Prof.) 126  … Symphsis: Secondary cartilaginous joints, bones are permanently interconnected by a fibrocartilage coated with a hard hyaline cartilage. This is a slightly movable type of cartilaginous joint. All midline joints of the body are said to be symphysis. E.g. pubic symphysis, manubrio-sternal symphysis and intervertebral joints. Yared Asmare(Asst Prof.) 127 , Yared Asmare(Asst Prof.) 128 Yared Asmare(Asst Prof.) 129 Cartilaginous joints Yared Asmare(Asst Prof.) 130  Synovial joints  Most common and important one  Joint is freely movable  Synovial joints are characterized by the following basic features: 1. Articular head (male part of a joint) the convex end of bone usually covered by a hyaline cartilage but sometimes by a fibrocartilage. 2. Articular fossa (Socket, Female part of a joint) a concave surface into which the head fits. It is similarly covered by an articular cartilage. 3. Articular (Synovial) cavity a thin capillary space b/n the articulating ends of bones and the articular capsule Yared Asmare(Asst Prof.) 131  Synovial joints… Articular capsule encloses the joint all around and it consists of two layers. a. An outer or fibrous layer (stratum fibrosum): Consists of dense irregular connective tissue composed of collagen and elastic fibers, hence also called fibrous capsule. This layer is reinforced or strengthened by ligaments and is continuous with the periosteum of the adjoining bones. It is free of blood vessels but contains receptors concerned with joint position and some sensory fibers conducting pain impulses. b. An inner or synovial layer (stratum synovial): Consists of loose CT composed of elastic fibers. The inner surface of the synovial membrane is lined by fibrocytes and macorophages (not by epithelium). This layer contains non-myelinated nerve fibers. Besides lining the inner surface of the articular capsule it covers all the internal surfaces of a joint notYared covered by cartilage. Asmare(Asst Prof.) 132  Synovial joints… Synovial fluid (synovia):  produced and absorbed by the synovial membrane in to or out of the articular cavity. It serves as: A sliding (slippery) lubricant material so that there will be a reduced friction b/n the articulating ends of bones. A transport medium for the nutrition of the articular cartilage, which has no blood vessels.  The synovial fluid is formed by the fibrocytes of the synovial membrane.  It contains few glycoproteins (mucin), hyaluronic acid …  Hyaluronic acid is a glycosaminoglycan forming the gelatinous material in tissue spaces that acts as cement substance. Yared Asmare(Asst Prof.) 133  Synovial joints… Articular cartilage  Is hyaline cartilage, covering articulating surfaces of bones in a synovial joint.  The articular cartilage is nourished by diffusion from the synovial fluid and gets an additional nutritional supply from the subchondral vascular plexus. Yared Asmare(Asst Prof.) 134  Classification of Synovial joints Structurally based on the number of articulating bones. 1. Simple joint: when only two bones participate in the formation of a joint. e.g. shoulder joint. 2. Compound joint: when more than two bones take part in the formation of a joint. e.g. elbow joint. 3. Complex joint: when discs and menisci are involved. e.g. knee joint. Yared Asmare(Asst Prof.) 135 Yared Asmare(Asst Prof.) 136  Types of synovial joints o Plane joints  allow gliding or sliding movement (uniaxial) e.g. b/n scapula and clavicle b/n carpal and tarsal bones o Hinge joints permit flexion and extension only (uniaxial) e.g. elbow, knee and interphalangeal joints o Condyloid joints allow movement in two direction (biaxial) e.g. radiocarpal joint of the wrist and MCP joint o Saddle joints opposing surfaces of bones are like a saddle (biaxial) e.g. trapeziometacarpal at the base of the thumb (CMC joint of the thumb) o Ball and socket joints allow multidirectional movement (multi axial joint) e.g. shoulder and hip o Pivot joints allow rotation (uniaxial joint) e.g. at atlantoaxial joint, proximal radioulnar Yared Asmare(Asst Prof.) 137 Yared Asmare(Asst Prof.) 138 Yared Asmare(Asst Prof.) 139 Yared Asmare(Asst Prof.) 140  Other structures associated with synovial joint: Intervertebral Discs (IVD) and Menisci oIVDs are the spongy cushions that separate the bones of the spine. oA meniscus is a crescent-shaped fibrocartilaginous anatomical structure that, in contrast to an articular disc, only partly divides a joint cavity. oE.g. knee joint oDisc and meniscus are structures found within the articular cavity consisting of connective tissue of fibrocartilage. oe.g. temporomandibular joint, intervertebral joint, where as menisci divide it partly oIVD divide an articular cavity completely whereas meniscus divide it partly. oImportant for directing of a given movement in a joint & for the uniform distribution of pressure on the bones Yared Asmare(Asst Prof.) 141 Yared Asmare(Asst Prof.) 142  … Synovial bursae Are small flattened fibrous bag filled with synovial fluid Found b/n the joints and their surrounding muscles, tendons, and ligaments that move on each other Reduce friction Two types Some of them communicate with the articular cavity (communicating bursae) and therefore directly affected by diseases of the joint and others are non-communicating bursae having no direct communication with the articular cavity. Articular labrum (lip) oArticular labrum enlarges the articular fossa of the socket so that the articular head of a bone correctly fits into its socket to form a stable joint. E.g. glenoidal labrum in the shoulder joint, acetabular labrum in the hip joint. Yared Asmare(Asst Prof.) 143 Yared Asmare(Asst Prof.) 144 Yared Asmare(Asst Prof.) 145  Ligaments oAre CT structures that hold the body together oTherefore two major types of ligaments are distinguished: 1. Those that connect the viscera together 2. Those that connect bones together oThose ligaments joining bones are of three types: a. Reinforcing (Strengthening) ligs:  providing support and strength to the articular capsule. b. Guiding (directing) ligs:  determine the type and direction of movement in a given joint. c. Restricting ligs:  they limit the extent of a joint movement. Yared Asmare(Asst Prof.) 146 Yared Asmare(Asst Prof.) 147 Some clinical terms related to bones and joints  Joints are usually injured by tensional and compressional forces applied on them.  Therefore, there are some terms related to these injuries. 1. Contusion: injury by increased compression. 2. Distortion: injury by increased tension. 3. Ligament or capsular rapture. 4. Dislocation (Luxation or subluxation)  when bones of a joint are forced out of a ligament, commonest site being the shoulder joint. 5. Rapture and herniation of discs and menisci  usually due to excessive compression. 6. Sprain  when the ligaments reinforcing a joint are over stretched of torn. 7. Osteitis  inflammation of a bone. Yared Asmare(Asst Prof.) 148 8. Osteochondristis  inflammation of a bone and its cartilage. 9. Osteomyelitis  inflammation of a bone and its marrow. 10. Osteoarthritis (Osteoarthrosis)  degenerative disease of bone and articular cartilage. 11. Osteosarcoma  maligament cancer of a bone. 12. Osteomalacia  adult rickets 13. Osteoporosis  atrophy of skeletal tissue in old age. 14. Bursitis  Inflammation bursae ,e.g. Housemaid’s knee or subcutaneous pre patellar bursitis, students elbow of olecranon bursitis. 15. Tendosynovitis  Inflammation of a tendon and its synovial sheath at the level of joints, also called tendovaginitis. 16. Arthritis  disease of the joints, which can be caused by infection (e.g. Pyogenic athrists, lyme’s disease) or degenerative process like osteoarthritis. Yared Asmare(Asst Prof.) 149 The muscular system Yared Asmare(Asst Prof.) 150. Yared Asmare(Asst Prof.) 151  Introduction Myology (Sarcology): is science concerned with muscles and their accessory parts like tendons, aponeurosis & fasciae. Muscle is from a Latin word meaning “little mouse,” a name given because flexing muscles look like mice scurrying beneath the skin. Muscle is made up of proteins and water Muscles are organs that are capable of contraction, which is important for movement, stabilizing body positions, storing and moving substances within the body and generating heat. 152 Prof.) Yared Asmare(Asst  Muscle functions 1. Motion.  Skeletal muscle attaches to the skeleton and moves the body by moving the bones.  Skeletal muscles help to move the body or its appendages.  Contraction of cardiac muscles pumps blood to the body  All involuntary body movements performed by smooth muscles  The muscle in the walls of visceral organs produces movement by squeezing fluids and other substances through these hollow organs. 2. Maintenance of posture. At times, certain skeletal muscles contract continuously to maintain posture, enabling the body to remain in a standing or sitting position. The skeletal system offers form and stability to the body Skeletal muscles maintain posture & support around flexible joints. 153 Prof.) Yared Asmare(Asst  Muscle Function 3. Joint stabilization. 4. Heat generation.  Muscle contractions produce heat that plays a vital role in maintaining normal body temperature at 37°C (98.6°F).  Involuntary contractions of skeletal muscles, known as shivering, can increase the rate of heat production. Body temperature is remarkable consistent. Metabolism with in the cells releases heat as end product Rate of heat production increases immensely during exercises 154 Yared Asmare(Asst Prof.)  Muscle tissue special functional characteristics 1. Contractility. One significant characteristic is that muscle contracts forcefully. Muscle cells shorten and generate a strong pulling force as they contract. 2. Excitability.  Nerve signals or other factors excite muscle cells, causing electrical impulses to travel along the cells’ plasma membrane.  These impulses then stimulate the cells to contract. 155 Prof.) Yared Asmare(Asst  … 3. Extensibility. is the ability of muscular tissue to stretch, within limits, without being damaged.  The connective tissue within the muscle limits the range of extensibility and keeps it within the contractile range of the muscle cells. 4. Elasticity.  is the ability of muscular tissue to return to its original length and shape after contraction or extension. 156 Yared Asmare(Asst Prof.)  TYPES OF MUSCLES a. Muscles can be classified based their location: Skeletal Cardiac Smooth. b. According to their microscopic appearance Cross striated Non- striated c. According to their function or innervations Voluntary Involuntary 157 Prof.) Yared Asmare(Asst  Skeletal muscle form and structure ⃙Is packaged in to skeletal muscle (that attach to & move the skeleton) ⃙As the name indicate these muscles are attached to the skeleton by a dense regular connective tissue(tendon or aponeurosis). ⃙Skeletal muscle pass from one bone to another across one or more joints so that contraction of the muscle results in movement at these joints. Yared Asmare(Asst 158 Prof.)  Skeletal muscle form and structure There are cross striated muscles not attached to the skeletal. e.g. Mimic muscle (muscle of facial expression) which are partly inserted to the skin of face Extrinsic muscle of the eye Muscles of the tongue Muscle of the larynx Muscle of the pharynx Muscle of the upper esophagus There are about 640 skeletal muscles in the human body constituting about 40% of the body weight. Skeletal muscle are innervated by voluntary or somatic nerves which arise either from cranial or spinal nerves. Yared Asmare(Asst 159 Prof.)  Basic feature of a skeletal muscle  Connective tissue investment CT surrounds and protects muscle tissue oFascia: oBroad band of fibrous CT that supports & surrounds muscle and other organs of the body Three layers of CT extend from deep fascia to further protect and strengthen skeletal muscle √Epimysium: surrounds the whole muscle (group of fascicles) √Perimysium: surrounds the fascicles(group of muscle fibers) √Endomysium: surrounds each muscle fiber 160 Prof.) Yared Asmare(Asst Anatomy of skeletal muscles Epimysium tendo perimysium n Muscle Fascicle Surrounded by perimysium Skeletal endomy muscle sium Skeletal Surrounded muscle fiber by epimysium (cell) Surrounded Yared Asmare(Asst Prof.) by 161 endomysium  Nerves and Blood Vessels  In general, each skeletal muscle is supplied by one nerve, one artery & one or more veins.  Each muscle fiber in a skeletal muscle is contacted by one nerve ending, which signals the fiber to contract such a contact is called neuromuscular junction.  A skeletal muscle fiber cannot contract unless it is stimulated by a nerve impulse. 162 Prof.) Yared Asmare(Asst  Muscle attachments Skeletal muscle is connected to the bone by a tendon and extend from one bone to another. When such muscle contracts, it causes one of these bones to move while the other one remains fixed. ±The less movable attachment of a muscle is called origin, whereas the movable attachment is the insertion. ± i.e. Thus, the insertion is pulled to ward the origin ®In the muscles of limbs, the origin lies proximal to the insertion. ®The fleshy thickened portion of a muscle is referred to as its belly. ®Some muscles are not attached to bone of both ends. ®Some muscles have more than one origin. 163 Prof.) Yared Asmare(Asst  Muscle attachments. Yared Asmare(Asst Prof.) 164  Types of skeletal muscle fibers  Based on two characteristics: How they manufacture energy(ATP) How quickly they contract  Muscle fibers are divided into three general classes: Slow Oxidative Fibers(red) Fast Glycolytic Fibers(white) Fast Oxidative Fibers (Intermediate) 165 Prof.) Yared Asmare(Asst Criteria Slow Oxidative Fast Oxidative Fast Glycolytic fibers fibers fibers Structural characteristics Fiber diameter Smallest Intermediate Largest Myoglobin Large amount Large amount Small amount content Mitochondria Many Many Few Capillaries Many Many Few Color Red Red-Pink White/Pale Yared Asmare(Asst Prof.) 166  … Slow oxidative fibres:  are thin, so they do not generate much power.  e.g. postural muscles of the lower back regions. Fast glycolytic fibers: © appear pale because they contain little Hgb. © 2x the diameter of SOF © Contain more myofilaments and generate much more power © Contain few mitochondria and capillaries but large glycosomes containing glycogen as a fuel. © E.g. muscles of the upper limb 167 Prof.) Yared Asmare(Asst Fast oxidative fibers ® Intermediate in their characteristics. ® Like FGF they contract quickly; like SOF they are oxygen dependent and have high myoglobin content, a large mitochondria, and a rich supply of capillaries. ® They are fatigue resistant but less than SOF. ® Speed of contraction is b/n FGF and SOF. ® The diameter of fiber is also intermediate ® More powerful than SOF but not as powerful as FGF.  E.g. muscles of the lower limbs 168 Prof.) Yared Asmare(Asst Cardiac Muscle Tissue Muscle tissue of the heart wall. The contraction of cardiac muscle pumps blood through the blood vessels. Striated like skeletal muscle. Cardiac muscle fibers are smaller than skeletal muscle fibers and branched longitudinally. Contain one (occasionally two) centrally located nuclei. Ends of adjacent cells are connected through an intercellular junctional complex called the intercalated disc. No significant regeneration of cardiac muscle after damage, repaired by scar formation (fibroblasts). 169 Prof.) Yared Asmare(Asst Cardiac muscle tissue Yared Asmare(Asst Prof.) 170  Smooth Muscle Tissue Found in the walls of visceral organs such as the stomach, respiratory tubes, urinary bladder, uterus & intestines… Each smooth muscle fiber is a spindle shaped cell, with one centrally located nucleus. Are non-striated. The contraction of smooth muscle is slow, sustained and resistant to fatigue. Actively divide and regenerate. 171 Prof.) Yared Asmare(Asst Smooth Muscle Tissue Yared Asmare(Asst Prof.) 172 Yared Asmare(Asst Prof.) 173 Comparison of the three muscle tissues 174 Prof.) Yared Asmare(Asst  Morphological types of muscle Based on various shape or form and orientation of their fibers skeletal muscles are classified as follow: 1. According to their form and shape a. Fusiform (spindle shaped) e.g. Sartorius b. Flat muscle e.g. Muscles of anterior abdominal wall c. Quadratic muscle e.g. Quadratus lumborum muscle d. Triangular muscle e.g. Temporalis muscle Yared Asmare(Asst 175 Prof.)  Morphological types of muscle… 2. According to the number of heads a. Biceps e.g. biceps brachii, biceps femoris b. Triceps e.g. triceps brachii, triceps surae c. Quadriceps e. g. quadriceps femoris 3. According to the number of bellies Some times two or more bellies are interconnected by an intermediate tendons. a. Digastric b. Omohyoid c. Rectus abdominis Yared Asmare(Asst 176 Prof.) Yared Asmare(Asst Prof.) 177 Yared Asmare(Asst Prof.) 178  Muscle Architecture (Arrangement of Fascicles)  Skeletal muscles may be classified based on fiber arrangement  The major types of fiber arrangement are: 1. Parallel: Strap  the long axes of the fiber run parallel to the long axis of the muscle itself. E.g. Sternocleidomastoid muscle, Sartorious, & Rectus abdominus Fusiform spindle shaped with an expanded central belly. E.g. Biceps brachii 2. Convergent fan shaped muscle  The origin is broad and the fascicles converge toward the tendon of insertion. E.g. pectoralis major 179 Prof.) Yared Asmare(Asst  … 3. Pennate ® Feather shaped  the fibers are short and attach obliquely to a tendon that runs the whole length of the muscle o If the fibers insert in to only one side of the tendon the muscle is unipennate e.g. Flexor pollicis longus. o If the fibers insert in to the tendon from both sides the arrangement is bipennate e.g. Rectus femoris muscle. o Multipennate arrangement looks like many feathers situated side by side, with all their feathers inserting into one large tendon e.g. deltoid 4. Circular(Sphincter): Surround a body openings or orifice e.g. orbicularis oris & orbicularis oculi 180 Prof.) Yared Asmare(Asst Muscle Architecture (Arrangement of Fascicles) Yared Asmare(Asst Prof.) 181 Interaction of Skeletal Muscle √ For muscles to create a movement, they can only pull, not push √ Muscles in the body rarely work alone, & are usually arranged in functional groups surrounding a joint √ A muscle that contracts to create the desired action is known as an agonist or prime mover √ A muscle that helps the agonist is a synergist √ A muscle that opposes the action of the agonist, therefore undoing the desired action is an antagonist Yared Asmare(Asst Prof.) 182  … Function of muscle Muscle do not function alone, that is they act together in groups. Based on their function and innervations muscle are group as follows. I. Genetic muscle group ⃙They develop from the same embryological source, therefore all of them are innervated by the same nerve. ⃙E.g. Muscle of facial expression (mimic muscle) developed from second brachial arch and innervated by facial nerve. Yared Asmare(Asst Prof.) 183  II. Functional muscle groups:  are groups of muscle with similar function that act together. E.g. flexors, extensors, abductor, adductor, and rotators. have different embryological origin and possibly innervated by different nerves. Within this group A. Agonist or primary movers. Some muscles are constantly active in initiating and maintaining a particular movement. referred to as agonist or primary movers. E.g. brachialis muscles in the flexor of elbow. B. Synergists  Some groups act together with or assist the activity of the agonist these are known as synergists. C. Antagonists: ⃙Make the contrary movement to the synergist. ⃙If synergists and antagonists act together on a given joint they will inhibit or lock the movement and stabilize the joint. ⃙A single muscle may be involved in several movement and play different roles i.e. it may be a prime mover, synergist, fixator or antagonist at different times.. Yared Asmare(Asst Prof.) 184  Nerve and blood vessel of skeletal muscle Due to the high energy and oxygen demand skeletal muscles are rich in blood vessels. The flow of blood through these vessels raised during muscular activity by dilation of the vessels. The change in the flow of blood through these vessels is regulated by the autonomic motor nerves that innervate the smooth muscle cells in the wall of blood vessels. They are also supplied by motor and sensory nerve fibers.  Fibers of the motor nerves are connected to a number of muscle fibers at a myoneural junction called motor end plate.  Muscle fibers that are innervated by a single motor neuron build- up a motor unit. Yared Asmare(Asst Prof.) 185. Yared Asmare(Asst Prof.) 186  … ⃙The sensory fiber carry proprioceptive impulse (deep sensation) from the receptor (E.g. muscle and tendon spindle) to the central nervous system. o Proprioception: perception or awareness of the position and movement of the body. ⃙Nerves and vessels enter a muscle at its hilum that lies at or near the middle of the muscle. Yared Asmare(Asst Prof.) 187 Yared Asmare(Asst Prof.) 188 Yared Asmare(Asst Prof.) 189 Structure associated with muscle (accessory structures ) ⃙Muscle form the active part of the locomotors system. ⃙Muscle is supported by other associated structures like tendons, aponeurosis, fascia, bursae, and tendon receptor organs(proprioceptors) and sesamoid bones 1. Tendons and Aponeurosis A. Tendon: ⃙a fibrous cord or band, mainly made from collagen fibres, that connects a muscle to bone or other structures. ⃙is a highly organized connective tissue joining muscle to bone, capable of resisting high tensile forces while transmitting forces from muscle to bone.  The dense, regularly arranged collagenous tissue is made up of fibers, cells of various shapes and ground substance. Yared Asmare(Asst 190 Prof.)  Accessory structures… B. Aponeurosis: a fibrous sheet or expanded tendon, giving attachment to flat muscles, serving as origin or insertion. Both tendons and aponuerosis are composed of dense collagenous connective tissue. The collagen fibers of tendons or aponeurosis are connected to muscle fibers at junctions called musculotendinous (myotendinous) junctions. Yared Asmare(Asst Prof.) 191 Tendons vs. Aponeurosis Yared Asmare(Asst Prof.) 192  Accessory structures…  The long tendons of the leg and arm muscles are covered by a tendon sheath (Vagina tendinis), specially at places where they change their running course or direction around a bony prominence.  A tendons sheath consists of: a. A fibrous outer layer (vagina fibrosa tendinis ) – composed of collagen and elastic fiber. b. An inner loose connective tissue contain blood vessels and nerves. Yared Asmare(Asst 193 Prof.) 2. Fascia From (Latin: "band") is a band or sheet of connective tissue, primarily collagen, beneath the skin that attaches, stabilizes, encloses, and separates muscles and other internal organs. Fascia consists of a dense collagenous connective tissue sheath covering a single muscle, group of muscles, an organ, a body part (e.g. arm, leg ) or the body as a whole. i.e. fascia is an envelop of collagenous tissue covering whole body. Beneath the skin the various structures that make up the body are held together by a connective tissue called fascia. Yared Asmare(Asst 194 Prof.) Yared Asmare(Asst Prof.) 195  Types of fascia  There are three main types of fascia: Superficial Fascia, which is mostly associated with the skin; Deep Fascia, which is mostly associated with the muscles, bones, nerves and blood vessels; and. Visceral (or Subserous) Fascia, which is mostly associated with the internal organs Yared Asmare(Asst Prof.) 196  2. Fascia… ⃙Fascia of muscles does not only covered muscles but also separates different muscles and group of muscles. ⃙The fascia of the body is divided in to superficial and deep. oThe superficial fascia is fat containing subcutaneous tissue found b/n the muscle and overlying skin. Its thickness and fat content varies in distribution depending on age, sex and diet. It contains small blood vessel, nerves, and some muscles (muscles in the face). In place where movement b/n the skin and under lying structure undesirable (e.g. scalp, sole of the foot, palm of the hand) it is fused with the deep fascia by bundle of collagen fiber. Yared Asmare(Asst Prof.) 197 The deep fascia Contains many compactly arranged collagen fibers often indistinguishable to the aponeurosis in wrapping material surrounding muscle or other organ forming a tough inelastic sheath. Function: ⃙It ensheathes muscles ⃙Helps as an attachment for muscles ⃙Separates muscle groups by forming intramuscular septae ⃙In the region of the wrist and ankle it forms retinacula that hold tendons crossing these joints in place. The deep fascia includes the palmar and plantar fasciae which are mainly protective in function. Yared Asmare(Asst Prof.) 198  Fascia… Fasciae of muscles are again of two types a. Single fascia  covers a single muscle and separates it from its neighbors. b. Group fascia  covers muscle groups that have similar functions and separates them from other groups. Some group fasciae can extend to the underlying bones.  Such extension of fascia, usually in the limb that lie b/n groups of muscles form Intermuscular septae. oseptae serve as origins and insertions for muscles, whereby they are also reinforced.  Fascia also form a protective covering around muscles, so that infection can not spread b/n adjacent muscles or group of muscles Yared Asmare(Asst 199 Prof.)  … 3. Synovial bursae They are found at places where: a tendon rubs against a bone, a ligament, other tendon, a muscle the skin moves over a bony prominence they help in the uniform distribution act as padding against injury caused by pressure. They may develop in response to friction and facilitate movement by the reduction of friction. 4. Sesamoid bone  These are found in some tendons increasing the lever effect and prevent the compression of tendons b/ n the articular ends of bones. Yared Asmare(Asst 200 Prof.)  … 5. Muscle and tendon receptor organs(proprioceptors) a. Muscle spindle(neuromuscular spindle) – controls the length of a muscle i.e. it is stimulated by the stretch of a muscle. b. Tendon spindle (Golgi tendon organ) – controls muscle tone. c. Golgi mazzoni bodies (found in the articular capsule ) and pacinian corpuscles for the determination of joint position Yared Asmare(Asst 201 Prof.) Tendon, aponeurossis, fascia and epimysium Yared Asmare(Asst Prof.) 202 Yared Asmare(Asst Prof.) 203 Aponeurosis and tendon Yared Asmare(Asst Prof.) 204 Layers of anterolateral abdominal wall Yared Asmare(Asst Prof.) 205 Muscular Hypertrophy oThe muscle growth that occurs after birth occurs by enlargement of existing muscle fibers, called muscular hypertrophy rather than by muscular hyperplasia, an increase in the number of fibers. oMuscular hypertrophy is due to increased production of myofibrils, mitochondria, sarcoplasmic reticulum, and other organelles. 206 Prof.) Yared Asmare(Asst  … oMuscular atrophy is a wasting away of muscles. oIndividual muscle fibers decrease in size as a result of progressive loss of myofibrils. oMuscular atrophy that occurs because muscles are not used is termed disuse atrophy. oDenervation atrophy… occurs when the nerve supply to a muscle is disrupted or cut, the muscle undergoes denervation atrophy. oMyalgia  Pain in or associated with muscles. oMyoma A tumor consisting of muscle tissue. oMyomalacia Pathological softening of muscle tissue 207 Yared Asmare(Asst Prof.)  MEDICAL TERMINOLOGY Myositis  Inflammation of muscle fibers (cells). Volkmann’s contracture Permanent shortening (contracture) of a muscle due to replacement of destroyed muscle fibers by fibrous connective tissue, which lacks extensibility. Hypotonia  refers to decreased or lost muscle tone. Such muscles are said to be flaccid. Flaccid muscles are loose and appear flattened rather than rounded. Hypertonia  refers to increased muscle tone and is expressed in two ways: spasticity or rigidity. 208 Prof.) Yared Asmare(Asst  Intramuscular Injections Intramuscular (IM) injection is penetration of the skin and subcutaneous layer to enter the muscle itself. Intramuscular injections are preferred when: ⃙rapid absorption is desired ⃙larger doses than can be given subcutaneously are indicated ⃙the drug is too irritating to give subcutaneously. The common sites for intramuscular injections include the: ⃙gluteus medius muscle of the buttock ⃙lateral side of the thigh in the midportion of the vastus lateralis muscle ⃙the deltoid muscle of the shoulder. 209 Prof.) Yared Asmare(Asst  Intramuscular Injections Muscles in these areas, especially the gluteal muscles in the buttock, are fairly thick, and absorption is promoted by their extensive blood supply. To avoid injury, intramuscular injections are given deep within the muscle, away from major nerves and blood vessels. IM injections have a faster speed of delivery than oral medications but are slower than intravenous infusions. 210 Prof.) Yared Asmare(Asst  Classification of Muscles Muscles of the Axial Skeleton o Include those responsible for facial expression, mastication, eye movement, tongue movement, respiration; and those of the abdominal wall and the pelvic outlet. Muscles of the Appendicular Skeleton o Includes muscles of the pectoral girdle, arm, forearm, wrist, hand, pelvic girdle, thigh, leg and foot. 211 Prof.) Yared Asmare(Asst  Skeletal muscles 212 Prof.) Yared Asmare(Asst Yared Asmare(Asst Prof.) 213 Circulatory System Yared Asmare(Asst Prof.) 214  Circulation is…  The continuous movement of blood throughout the body, driven by the pumping action of the heart.  On average, it takes about 45 seconds for blood to circulate from the heart, all around the body, and back to the heart again. Yared Asmare(Asst Prof.) 215  Function of the Circulatory System Formation of blood transportation network oHeart pumps blood oBlood carries nutrients, oxygen, hormones and waste products to and from the cells oRegulate body temperature Drainage of surplus tissue fluid and leaked plasma proteins to the bloodstream, as well for the removal of debris from cellular decomposition and infection Absorption of dietary fat Formation of a defense mechanism of the body Yared Asmare(Asst Prof.) 216  Components of the Circulatory System The circulatory system is subdivided into: a. Cardiovascular system blood heart blood vessels b. Lymphatic system (vessels that carry a fluid called lymph) Yared Asmare(Asst Prof.) 217 Yared Asmare(Asst Prof.) 218 Yared Asmare(Asst Prof.) 219  Functions of Blood Transport of: Gases, nutrients, waste products Processed molecules Regulatory molecules Regulation of pH and osmosis Maintenance of body temperature Protection against foreign substances Clot formation Yared Asmare(Asst Prof.) 220  Composition of Blood Blood is composed of: Plasma 55 % Formed elements (45%) oErythrocyte oLeukocyte oPlatelets Plasma 55% Buffy coat Erythrocyte 45% Centrifuge Yared Asmare(Asst Prof.) 221  After centrifuge the massive formed element laying at the base is erythrocyte Hematocrit: percentage of blood volume that contain erythrocyte Average 45 % In male 47%± 5% In female 42% ±5% In newborns 42%-68% Buffy coat lie b/n erythrocyte and plasma containing leukocyte and platelets Plasma makes topmost part accounting 55% Yared Asmare(Asst Prof.) 222 Yared Asmare(Asst Prof.) 223  Blood Cell Formation  Hematopoiesis or hemopoiesis: process by which blood cells are formed Begins in the early embryo continues throughout life. Bone marrow is the site of blood cell formation Bone marrow: occupies the interior of all the bones Red bone marrow: actively generate blood cells Yellow bone marrow: dormant but become active in emergencies. It contains many fat cells Yared Asmare(Asst Prof.) 224  At birth, all marrow in the skeleton is red. In adults, red marrow remains: between the trabeculae of spongy bone throughout the axial skeleton and girdles in the proximal epiphysis of each humerus & femur Yellow marrow occupies all other regions of the long bones of the limbs. The replacement of red marrow with yellow marrow in the limbs occurs between the ages of 8 and 18 years. Yared Asmare(Asst Prof.) 225  Cell Lines in Blood Cell Formation All blood cells arise from one cell type, the blood stem cell. Stem cells divide continuously: to renew themselves to produce lines of progenitor cells that lead to the various blood cells The two types of progenitor cells that arise directly from blood stem cells are: Lymphoid stem cells: give rise to lymphocytes Myeloid stem cells: which give rise to all other blood cells. Yared Asmare(Asst Prof.) 226 Hematopoiesis Yared Asmare(Asst Prof.) 227 Some important terms related to the circulatory system 1. Plexus: a network of interjoining venous vessels (also applied to nerves and lymphatic vessels). E.g.  Venous plexus of the scalp.  Pharyngeal venous plexus.  Suboccipital venous plexus.  Oesophageal venous plexus.  Rectal venous plexus. 2. Sinus: a channel for the passage of blood or lymph, without the coats of an ordinary vessel, e.g. cerebral meninges/dural venous sinus 3. Sinusoid: very wide capillary found in the liver and endocrine glands, spleen etc.  Their lining endothelial cells are capable of engulfing particulate matter (phagocytosis). Yared Asmare(Asst Prof.) 228  Terms related to the circulatory system… 4. Collateral circulation: is alternate or “backup” blood vessels in your body that can take over when another artery or vein becomes blocked or damaged. This is a circulation maintained by small anastomosing vessels when the main vessel is obstructed, so that the blood supply to an organ would be constant. The lumen of these small collateral vessels increases in diameter due to the increased volume to be transported. Collateral circulation provides alternative routes for blood flow. A collateral circulation can be adequate (sufficient) or inadequate (insufficient). o adequate: E.g. vessels of the GIT o inadequate: E.g. coronary arteries Yared Asmare(Asst Prof.) 229  Terms related to the circulatory system…  The coronary arteries, even though they form anastomosis the collateral circulation in them is inadequate, therefore they are said to be functional end arteries.  End arteries are the only supply of oxygenated blood to a tissue or organ. Other examples to such arteries are vessels of the brain, lungs, liver, kidneys, spleen and metaphysis of long bones.  When an artery has no collaterals or forms no anastomosis with other vessels it is known as end artery, e.g. central retinal artery.  The blockage of a functional end artery or an end artery results in the ischemia, infarction and then necrosis or death of the concerned tissue. Yared Asmare(Asst Prof.) 230  Terms related to the circulatory system… 5. Anastomosis: a communication between arteries, veins and lymphatic vessels. E.g. portocaval anastomosis 6. Venae comitantes: arteries are usually accompanied by veins and lymphatic vessels sharing a common inelastic connective tissue sheath. While a one-to-one artery to vein relation applies for many large vessels; two veins accompany the smaller arteries. These two veins accompanying a single artery are called venae comitantes. Yared Asmare(Asst Prof.) 231  Terms related to the circulatory system… 7. Neurovascular bundle: vascular bundles contain their own vasomotor nerve networks, but in addition they may be accompanied by major nerve trunks forming a neurovascular bundle. E.g. Neurovascular bundle of the neck (common carotid artery, internal jugular vein and vagus nerve). Neurovascular bundle of the thigh (femoral artery, vein and nerve). Innervation of blood vessels Blood vessels are predominantly innervated by sympathetic nerves that mainly cause vasoconstriction, but to a lesser extent by parasympathetic nerve, which are vasodilators. Yared Asmare(Asst Prof.) 232  Blood vessels  tubular structures, with particular named layers from innermost to outermost: Tunica interna/intima Tunica media Tunica externa /adventitia Functions: Distribution of blood Exchange of materials with tissues (nutrient, oxygen, waste) Return of blood to the heart Transportation of hormones to their target organs Yared Asmare(Asst Prof.) 233  General Characteristics of Blood Vessels Tunica externa – Outermost layer – CT with elastin and collagen – Strengthens, anchors Tunica media – Middle layer – Circular smooth muscle – Vasoconstriction/dilation Tunica intima – Innermost layer – Endothelium – Minimize friction Lumen Yared Asmare(Asst Prof.) 234 General Structure Yared Asmare(Asst Prof.) 235  Types of Vessels Arteries  carry blood away from the heart Elastic arteries Muscular arteries Arterioles Veins  carry blood towards the heart Capillaries  the most important part of the vascular system; site of exchange of materials Continuous Fenestrated Sinusoidal Yared Asmare(Asst Prof.) 236 Yared Asmare(Asst Prof.) 237  Arteries Elastic /Conducting/Arteries Thick-walled arteries near the heart e.g. pulmonary artery, aorta and common carotid artery Large lumen allows low-resistance conduction of blood. Contain lots of elastin in all three tunics. Walls stretch and recoil to propel blood Withstand and regulate large blood pressure fluctuations. Yared Asmare(Asst Prof.) 238 Muscular (Distributing) Arteries Medium sized vessels Tunica media more smooth muscle; less elastin Smooth muscle layers constitute 3/4 of wall thickness Major area of vaso-constriction & dilation to regulate blood flow E.g. femoral a, splenic a… Yared Asmare(Asst Prof.) 239 Arterioles Smallest arteries; lead to capillary beds Diameter of 0.3 mm or less Close to capillaries  single layer of muscle spiralling around the endothelial lining Regulates blood flow to capillary Metarterioles Short vessels connect arterioles to capillaries Muscle cells form a precapillary sphincter about entrance to capillary Yared Asmare(Asst Prof.) 240 Capillaries Smallest vessels – diameter just large enough for a red blood cell Walls consist of tunica intima only (i.e. layer of endothelium) Thinness facil