General Gross Anatomy PDF

# Anatomy ## General Gross Anatomy ### Anatomical Terms and Planes - Anatomical Position - standing erect and facing forwards, upper limbs by the side with the palms facing forwards, and lower limb together with the toes facing forwards - Four Imaginary Planes - Median (midsagittal) plane - p...

# Anatomy ## General Gross Anatomy ### Anatomical Terms and Planes - Anatomical Position - standing erect and facing forwards, upper limbs by the side with the palms facing forwards, and lower limb together with the toes facing forwards - Four Imaginary Planes - Median (midsagittal) plane - passes longitudinally through the body and divides it into right and left halves - Sagittal plane - any vertical planes parallel with the median plane - Coronal (frontal) plane - passes at right angle to the median plane and divides the body into anterior (front) and posterior (back) - Horizontal (transverse) plane - passes at right angles to both median and sagittal planes, dividing the body into superior (upper) and inferior (lower) parts - Sections of the Body - Longitudinal sections - run parallel to the long axis of the body or of any of its parts, regardless of the position of the body - Transverse sections, or cross sections, - cut at right angles to the longitudinal axis of the body or of any of its parts - Oblique sections - not cut along the previously listed anatomical planes, they are slightly oblique - Terms of Relationship and Comparison - Superior (cranial) - nearer to the head - Inferior (caudal) - nearer to the feet - Posterior (dorsal) - nearer to the back - Anterior (ventral) - nearer to the front - Central - towards the center of the mass - Peripheral - away from the center of the mass - Median - along the median plane - Medial - nearer to the median plane of the body - Lateral - farther away from the median plane - External - outside of or farther from the center of an organ or cavity - Internal - inside or closer to the center - Superficial - nearer to the surface - Deep - farther from the surface - Proximal - nearer to the trunk or point of origin (e.g. of a limb) - Distal - farther from the trunk or point of origin (e.g. of a limb) ### Terms of Laterality - Bilateral - paired structures having right and left members - Unilateral - occurring on one side only - Ipsilateral - occurring on the same side of the body as another structure - Contralateral - occurring on the opposite side of the body relative to another structure ### Terms of Movement - Flexion - bending or decreasing the angle between the bones or parts of the body - Dorsiflexion - flexion at the ankle joint, Plantarflexion - bends the foot and toes toward the ground - Extension - straightening or increasing the angle between the bones or parts of the body. - Abduction - moving away from the median plane - Adduction - moving toward the median plane - Circumduction - circular movement that involves sequential flexion, abduction, extension, and adduction (or in the opposite order) - Medial rotation (internal rotation) - brings the anterior surface of a limb closer to the median plane - Lateral rotation (external rotation) - takes the anterior surface away from the median plane - Pronation - rotation of the radius medially so that the palm of the hand faces posteriorly and its dorsum faces anteriorly - Supination - rotation of the radius laterally and uncrossing it from the ulna, returning the pronated forearm to the anatomical position - Eversion - movement of the sole of the foot in which the sole faces outwards and laterally - Inversion - movement of the sole of the foot in which the sole faces inwards and medially - Opposition - movement by which the 1st digit (thumb) is brought to another digit - Reposition - movement of the 1st digit from opposition back to its anatomical position - Protrusion (protraction) - movement in which a part of the body moves forwards on a plane parallel to the ground - Retrusion (retraction) - movement in which a part of the body moves backwards on a plane parallel to the ground - Elevation - raises or moves a part superiorly - Depression - lowers or moves a part inferiorly ### References - Moore, K. L., Dalley, A. F. and Agur, A. M. R. (2018) Clinically Oriented Anatomy. 8th ed. Philadelphia: Wolters Kluwer. pg.90-103. - Patton, K. T. and Thibodeau, G. A. (2013) Anatomy & Physiology. 8th ed. Missouri: Elsevier. pg.15-16. - Singh, V. (2015) General Anatomy with Systemic Anatomy, Radiological Anatomy, Medical Genetics. 2nd ed. New Delhi: Elsevier. pg.12-18. - Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. 41st ed. Philadelphia: Elsevier. pg.xvi-xv ## Fascia - Fascia constitutes the wrapping, packing and insulating materials of the deep structures of the body. There are two basic layers named as, superficial and deep layers. ### Superficial Fascia - It is a subcutaneous layer of loose areolar tissue which unites dermis of skin to the underlying deep fascia. - It has a fatty superficial layer and a membranous deep layer. - The superficial fascia contains fat almost everywhere in the body except in the eyelids, external ear, penis, scrotum and flexion creases of the digits. - Amount of fat in superficial fascia is more in females and children. - In mature females, it tends to accumulate in the breasts, anterior abdominal wall below the umbilicus, gluteal, lumbar region and thighs. - In males, it accumulates in the lower abdominal wall. ### Functions of Superficial Fascia - Thermal insulation - Water and fat provides an effective barrier against rapid loss of body heat. - Protective cushion - Stored fat and water provides protection against mechanical shock (Eg. Buttocks) - Conduction - Contains nerves, vessels and lymphatics, which are transported to and from the skin above. ### Applied Anatomy - Subcutaneous injections are painful due to presence of pain receptors in it. Drugs administered by this route are absorbed slowly and only small doses (0.5-1 ml) of are given. - The ideal sites of subcutaneous injections are- anterior abdominal wall, anterior aspect of thigh and posterior aspect of arm. ### Deep Fascia - It is a dense, organized connective tissue layer, devoid of fat, that covers most of the body deep to the skin and subcutaneous tissue. - It is best marked in the limbs and neck. Its thickness varies widely and it is absent in face, breast, anterior abdominal wall, penis, scrotum and ischiorectal fossa. ### Functions of Deep Fascia - Deep fascia thickens to form retinaculum to retain the tendon of long muscles in place and prevent their bowstringing during action of these muscles. - Eg. flexor and extensor retinacula around wrist and ankle joint. - In palms and soles it thickens to form palmar and plantar aponeurosis to protect the underlying structures. - Deep fascia is modified to form interosseous membranes in the forearm and leg. - It splits to enclose certain glands to form their capsule, Eg. parotid gland, submandibular gland, thyroid gland, etc. - The ligaments of joints are considered as localized thickened bands of the deep fascia. - Deep fascia condenses to form a sheath around neurovascular bundles and provides pathway for their passage of vessels and nerves. Eg. Carotid sheath and Axillary sheath. - Deep fascia forms fibrous flexor sheath around the long flexor tendons so that tendons may move freely over one another frictionlessly. ### References - Moore, K. L., Dalley, A. F. and Agur, A. M. R. (2018) Clinically Oriented Anatomy. 8th ed. Philadelphia: Wolters Kluwer. pg.90-103. - Netter, 2019 - Moore, Dalley and Agur, 2017 ## Bone ### Introduction - A living structure composed of highly vascular and mineralized connective tissue - Composed of cells and intercellular substances ### Functions - Bony framework for form and support - Lever for movements in locomotion - Areas for attachment of muscles and ligaments - Protection of viscerae - Production of blood cells (by bone marrow) - Storage of calcium and phosphate ions - Transmission of weight and force ### Classification of Bones - According to development - Membranous bone - Developed from mesenchymal membrane - E.g. skull - Endochondral (cartilaginous) bone - Developed from the cartilaginous model - E.g. limb bones - According to structure - Compact bone - Dense in texture - Adaptation to bending and twisting forces - E.g. shaft of long bones - Spongy bone - Made up of a meshwork of trabeculae - Adaptation to compressive forces - E.g. ends of long bones, short bones - According to region - Axial bone - Bones of the head, neck and trunk - E.g. skull, vertebra, ribs - Appendicular bone - Bones of limbs and girdles - E.g. scapula, humerus, femur - According to maturation - Immature bone - Foetal bone - Mature bone - Adult bone - According to Shape - Long bones - Length greater than breadth and thickness - Tubular with marrow cavity inside - Develops in cartilage (exception – clavicle) - E.g. only found in bones of limbs - Short bones - Dimensions nearly equal - Cuboid in shape - Spongy bone and marrow cavity enclosed by a thin compact bone - Develops in cartilage - E.g. carpals, tarsals - Flat bones - Two layers of compact bone with spongy bone and marrow cavity between them (like a sandwich) - Spongy layer in bones of the skull vault is called diploe. - E.g. sternum, scapula, most skull bones - Irregular bones - Irregular in shape - E.g. vertebra, hip bone, temporal bone - Sesamoid bone - Nodules of bones embedded in some tendons exposed to pressure and friction - E.g. patella - Accessory bone - Bones that are not regularly present - E.g. supernumerary digit, sutural bones of skull - Pneumatic bone - Skull bones with air cavities - E.g. ethmoid bone, frontal, maxillary, sphenoid - Heterotopic bone - Pieces of bones found in places other than normal sites - E.g. scars, calcified tendons ### Parts of A Young Long Bone - Each long bone has a shaft (diaphysis) and two ends (epiphyses). - Diaphysis (shaft of the bone) - Thick-walled tube made up of compact bone surrounding a medullary (marrow) cavity - Marrow cavity contains red or yellow marrow - Red marrow in most of the long bones in a child - Replaced by yellow marrow with age - Site of primary ossification - Metaphysis - End of diaphysis adjacent to epiphysis - Separated from epiphysis by epiphyseal disc - Growth zone of the bone where growth in length occurs - When the growth in length ceases the epiphyseal plates become bone. - Epiphyses - Usually wider than the shaft - Made up of spongy bone covered with a thin compact bone - Sites of secondary ossification - Articular surfaces are covered by articular cartilage (hyaline cartilage). - Coverings - Periosteum - Connective tissue covering outer surface of long bone except at articular surfaces - Has outer fibrous limiting membrane and inner cellular layer (for new bone formation) - Endosteum - Thin cellular membrane lining marrow cavity of compact bone and trabecular spaces of spongy bone ### Blood Supply of A Long Bone - Arterial supply - Nutrient artery - Usually a branch of a larger artery running adjacent to the bone - Enters the shaft through nutrient foramen - Divides into proximal and distal branches - Supplies spongy bone and inner part of compact bone up to metaphysis - Branches of periosteal arteries - Supplies outer part of compact bone of the shaft - Epiphyseal and metaphyseal arteries - Supply epiphysis, metaphysis and joint capsule - In a young growing bone, metaphyseal and epiphyseal arteries are separated by the epiphyseal disc. In mature bone, they anastomose freely with each other. - Venous drainage - Venous blood drains into medullary sinusoids and then into a large central venous sinus. - This sinus is drained by venae commitantes of nutrient, articular and periosteal arteries. ### Lymphatic Drainage and Nerve Supply - Lymphatic drainage - Lymph vessels in periosteum and peri-vascular lymph spaces - Nerve supply - Many nerves in bone accompanying the vessels (mainly vasomotor) - Sensory fibres in periosteum which is sensitive to tension and tear ### Development of Bones - Types of ossification - Membranous ossification - Direct ossification of mesenchymal cells - Occurs in skull, mandible, clavicle, terminal digits - Endochondral (cartilaginous) ossification - Hyaline cartilage model replaced by bone - Occurs in all long bones except the clavicle - Ossification centres - Primary ossification centre - First ossification centre to appear before birth - Usually appears at about 8th intra-uterine week and situated at middle of shaft in long bones - Ossification extends along the body of the bone in endochondral ossification - Secondary ossification centre - Ossification centre that appears after primary centre or appears for the first time after birth - Situated in epiphyses and appears at 1st or 2nd year of life in a long bone - Law of ossification - Epiphysis which is first to appear is the last to unite (exception – fibula) - Epiphysis of non-growing end unites with diaphysis at about 18 - 19 year of age - Epiphysis of growing end unites with diaphysis at about 21 year of age - Types of epiphysis - Pressure epiphysis - Transmits the body weight and protects the epiphyseal cartilage - E.g. head of femur, head of humerus - Traction epiphysis - Produced by pull of the attached muscle - E.g. greater and lesser trochanters of the femur - Atavistic epiphysis - A separate bone in lower animals, but fused with a nearby larger bone in humans - E.g. coracoid process of scapula - Aberrant epiphysis - Not always present - E.g. additional epiphysis in distal end of the first metacarpal (which usually has epiphysis in the proximal end) - Growing end of a long bone - Responsible for growth in the length of that bone - Is the end where epiphysis unites late with the diaphysis than the other - Direction of nutrient artery - Usually points away from growing end of a long bone ### Applied Anatomy - Fracture - A break in the continuity of a bone - Simple (closed) fracture - Fracture not connected with the skin wound - Compound (open) fracture - Fracture that communicates with the skin wound - Extensive blood supply of bones - Difficult to interrupt blood supply to kill the bone due to extensive blood supply - So, metal pins can be inserted into medullary cavity in fractures - Avascular necrosis - Loss of blood supply to a part of bone leading to death of bone tissue - Epiphyseal cartilage in X-ray - Seen as epiphyseal line - May be mistaken as a fracture - Bone marrow biopsy - For examination of bone marrow for various clinical conditions especially in blood disorders - Bone tumours - Benign or malignant tumours may occur ### References - Agur, A.M.R. & Dalley A.F. (2017) Grant's Atlas of Anatomy. 14th ed. Philadelphia, Wolters Kluwer: Pg.471. - Drake, R.L., Wayne Vogl, A. & Mitchell, A.W.L. (2020) Gray's Anatomy for Students. 4th ed. Elsevier: Pg.12-17. - Ellis, H. & Mahadevan, V (2019) Clinical Anatomy: Applied Anatomy for Students and Junior Doctors. 14th ed. Wiley Blackwell: Pg.408 - Gardner, E. Gray, D.J. & O'Rahilly, R (1975) Anatomy: A Regional Study of Human Structure. 4th ed. Philadelphia. W. B. Saunders Company: Pg.9-16 - Garg, K. (ed.) (2009) BD Chaurasia's Handbook of General Anatomy, 4th ed. New Delhi. CBS Publishers and Distributors Pvt. Ltd: Pg.29-56 - https://brainly.in/question/7546530 - https://radiologykey.com/general-anatomy-and-radiographic-positioning-terminology/ - https://courses.lumenlearning.com/boundless-ap/chapter/introduction-to-bone/ - Last, R.J. (1970) Anatomy: Regional and Applied. 4th ed. London. English Language Book Society and J & A Churchill: Pg. 14-18 - Moore, K.L., Dalley A.F. & Agur, A.M.R. (2014) Moore Clinically Oriented Anatomy. 7th Ed. Philadelphia, Wolters Kluwer: Pg 19-25 - Rawlani, S. & Rawlani, S. (2013) Textbook of General Anatomy. 2nd ed. New Delhi. Jaypee Brothers Medical Publishers (P) Ltd: Pg.43-77 - Sadler, T.W. (2019) Langman's Medical Embryology. 14th ed. Wolters Kluwer: Pg.174 - Standring, S. (editor-in-chief) (2016) Gray's Anatomy. 41st ed. Churchill Livingstone Elsevier: Pg.81-96 - Wineski, L.E. (2019) Snell's Clinical Anatomy by Regions. 10th ed. Philadelphia, Wolters Kluwer: Pg.33-45. ## Cartilage ### Definition: - Avascular, tough, resilient connective tissue. ### Functions: - Support of soft tissue - Sliding surface for joints for movements - For growth of long bones ### Types: - Hyaline Cartilage - Translucent, white, resilient in macroscopic appearance - Bony precursor in cartilaginous ossification - Articular cartilages (in synovial joints) - Costal cartilage - Cartilages of nose - Larynx, trachea, bronchi - Fibrocartilage - Tough, strong, resilient opaque - Found in places where tough support and tensile strength is needed - Intervertebral discs - Articular discs - Elastic cartilage - Found in places where stiffness together with elasticity is needed - External ear (auricle) - External acoustic meatus - Eustachian (auditory) tube - Epiglottis ### Growth: - By both interstitial and appositional growths - Slow growth in adult cartilage - Poor regeneration after injury - Interstitial growth - New cells formed within the substance of cartilage - Appositional growth - New cells formed from perichondrium are deposited onto the existing cartilage surface. ### Blood and nerve supply: - No blood vessel, lymphatics and nerves (nutrition by diffusion) ### Applied anatomy:: - If damaged, cartilage repairs itself slowly like other fibrous tissues. ### References - Agur, A.M.R. & Dalley A.F. (2017) Grant's Atlas of Anatomy. 14th ed. Philadelphia, Wolters Kluwer: Pg.471. - Drake, R.L., Wayne Vogl, A. & Mitchell, A.W.L. (2020) Gray's Anatomy for Students. 4th ed. Elsevier: Pg. 12-17. - Ellis, H. & Mahadevan, V (2019) Clinical Anatomy: Applied Anatomy for Students and Junior Doctors. 14th ed. Wiley Blackwell: Pg.408 - Gardner, E. Gray, D.J. & O'Rahilly, R (1975) Anatomy: A Regional Study of Human Structure. 4th ed. Philadelphia. W. B. Saunders Company: Pg.9-16 - Garg, K. (ed.) (2009) BD Chaurasia's Handbook of General Anatomy, 4th ed. New Delhi. CBS Publishers and Distributors Pvt. Ltd: Pg.29-56 - https://brainly.in/question/7546530 - https://radiologykey.com/general-anatomy-and-radiographic-positioning-terminology/ - https://courses.lumenlearning.com/boundless-ap/chapter/introduction-to-bone/ - Last, R.J. (1970) Anatomy: Regional and Applied. 4th ed. London. English Language Book Society and J & A Churchill: Pg. 14-18 - Moore, K.L., Dalley A.F. & Agur, A.M.R. (2014) Moore Clinically Oriented Anatomy. 7th Ed. Philadelphia, Wolters Kluwer: Pg 19-25 - Rawlani, S. & Rawlani, S. (2013) Textbook of General Anatomy. 2nd ed. New Delhi. Jaypee Brothers Medical Publishers (P) Ltd: Pg.43-77 - Sadler, T.W. (2019) Langman's Medical Embryology. 14th ed. Wolters Kluwer: Pg.174 - Standring, S. (editor-in-chief) (2016) Gray's Anatomy. 41st ed. Churchill Livingstone Elsevier: Pg.81-96 - Wineski, L.E. (2019) Snell's Clinical Anatomy by Regions. 10th ed. Philadelphia, Wolters Kluwer: Pg.33-45. ## Joints ### Definition - The sites where two skeletal elements come together are termed joints. ### Classification - Solid joints (No cavity and components are held together by connective tissues) - Synovial joint (Separated by cavity) - Solid Joints - Fibrous joints - Suture - Sutures are found only between the bones of skull. Eg. Sagittal suture - Syndesmosis - It is partially movable and in which the bony components further apart and united by a fibrous interosseous membrane. - Eg. Joint between radius and ulna, Joint between tibia and fibula - Gomphosis - Peg and socket articulation between root of the teeth and alveolar processes of the maxillary and mandibular bones - Schindylesis - It is a tongue and groove type of joint where one bone fits into a channeled groove of another. - Eg. Vomer of nasal septum fitting into the rostrum of the body of sphenoid bone. - Cartilaginous joints - Primary cartilaginous joint (or) Synchondrosis - The joint is a temporary union replaced by bone when growth ceases. - They develop between the bones of endochondral origin. - Eg. Joints between epiphyses and diaphysis of long bone. - Secondary cartilaginous joint (or) Symphyses - Partially movable type where opposing surfaces are covered hyaline with cartilage but separated from each other by intervening fibrous tissue or fibrocartilage. - Eg. Symphysis pubis, Between the joints of vertebral bodies - Synovial Joint - According to the Number of Articulating Surfaces - Simple - has only one pair of articulating surfaces. - Eg. joints of the fingers. - Compound - has more than one pair of articulating surfaces. - Eg. elbow joint. - Complex - The joint cavity is completely or partially divided by a disc or meniscus. - Eg. knee joint. - According to the Number of Axes - Uniaxial joint - It has only one degree of freedom. - Eg. hinge joint or pivot joint - Bi - axial joint - There are 2 axes of movement, 2 degree of freedom. - Eg. Saddle joint, Ellipsoidal joint. - Multi - axial or poly - axial - It has 3 degree of freedom and has axes in all planes. - Eg. ball and socket joint. - According to the Shape of the Articulating Surfaces - Plane Joint - The opposing surfaces are almost flat and allow movement in one plane only. - It is uni-axial with one degree of freedom. Eg. Intercarpal joints. - Hinge Joint or Ginglymus - It has one opposing surface slightly concave and the other slightly convex. - Eg. Humero -ulnar joint (elbow joint). - Pivot Joint - One of the opposing bones is encircled at the joint end by a fibrous ring or cuff, enabling the bone within the cuff to rotate along the vertical axis. It allows one degree of freedom. - Eg. Proximal radio - ulnar joint, dens of the axis and the atlas of the (atlanto - axial) joint - Ellipsoidal Joint - It resembles ball and socket joint but the articulating surfaces are much longer in one direction than the other. It allows two degree of freedom, biaxial. Eg. Radio carpal joint (wrist joint). - Saddle Joint - The opposing bony surfaces are reciprocally curved in a saddle shape and allows movement in two planes, bi - axial joint. - Eg. Carpo - metacarpal joint of thumb. - Ball and Socket Joint - One opposing bony surface is ball - shaped and other is reciprocal socket - thus allowing movement in all planes. - Eg. Shoulder joint, hip joint. - Condyloid (Bicondylar) Joint - The articular surface of each bone consists of two distinct articular surfaces, each called a condyle. It is a modified hinge joint. - Eg. Knee and T - M joint ### Characteristic Features - Synovial joint is freely movable joint and is typical of nearly all joints of upper and lower limbs. ### Stability of Joints - Factors contributing to the stability of joints consist of bony, ligamentous and muscular factor. - Atmospheric pressure is a negligible factor in most joints. - The importance of the three factors is nearly always in the ascending order of bone, ligament and muscle. - Bony Contours - In ball and socket joint as the hip, or ankle, bony contours play an important part; but in most joints (eg. shoulder, knee, arches of foot) they contribute nothing at all to stability. - Ligaments - Ligaments are an important factor in most joints, preventing over-movement and in guarding against sudden accidental stresses. - They are no value in guarding against continuous stress (eg., in supporting the arches of the foot), since they are composed of white fibrous tissue (collagen) which, once stretched, they remain elongated. - Elastic tissues in ligaments shorten after elongation. - Muscles - In almost all joints muscles are the most important. - In many joints an indispensable factor in maintaining stability. - Eg. The short muscles of the scapula are indispensable as fixators of the shoulder joint in all movements of the upper limb. - Degree of Movement - Increase degree of movement may cause the articulating surfaces to loose contact and thus become unstable. - Posture - Posture of the limb determine its stability. - Eg. hip joint is unstable when the leg is crossed at the knee, in this case the articulating surface is in least apposition. - Nerve Supply - Hilton's Law - The same trunk of nerve, whose branches supply the groups of muscles moving a joint. also supply the skin overlying the insertions of such muscle and the interior of the joint. ### Applied Anatomy - Joint replacement - Joint replacement is undertaken for a variety of reasons. It includes degenerative joint disease and joint destruction. Joints that have severely degenerated or lack their normal function are painful, and in otherwise can restrict activities of daily living. - Arthroscopy - Arthroscopy is a technique of visualizing the inside of a joint using a small camera placed through a tiny incision in the skin. Arthroscopy can be performed in the knee, shoulder, ankle, and hip joints. ### References - Biology for Majors II, https://courses.lumenlearning.com/wm-biology2/chapter/types-of-synovial-joints/ [Accessed on 16, June, 2020] - Drake, R.L., Wayne Vogl, A. & Mitchell, A.W.L (2020) Gray's Anatomy for students. 4th Edition. Elsevier. Pg. 20-25. - Ferry, A.T, Knee Arthroscopy, What is arthroscopic surgery, https:// amonferrymd.com/surgical- expertise/knee-arthroscopy/ [Accessed on 18, June, 2020] - Rawlani, S & Rawlani, S. (2011) Text book of General Anatomy. 1st Edition. New Delhi. Jaypee Brothers Medical Publishers (P) Ltd. Pg.80-89. - Standring, S. (2008) Gray's Anatomy. 40th Edition. Churchill Livingstone Elsevier. Pg.97-103. ## Muscle ### Definition: - The muscle or flesh is a specialized tissue which has the ability to contract to a great extent and produce movement. ### Classification: - Skeletal muscle (Voluntary, striated muscles) - Smooth muscle (Involuntary, non-striated muscle) - Cardiac muscle (Involuntary, striated muscle) ### General Characteristics of Skeletal Muscle - form muscle of limb, body wall and face. - attached to bone, typically cross at least one joint except in facial muscles, sphincter muscles (around the entrance to the oral cavity, mouth and anus). - they contract to bring two bony parts close together, they act on joints producing movement. - Capable of rapid and powerful contraction for moderate period with intervals for rehabilitation and also maintain prolonged state of tonus. ### Organization of Skeletal Muscle - Muscle fibre - basic anatomical unit. - Endomysium - connective tissue sheath surrounding each muscle fibre. - Perimysium - connective tissue sheath surrounding bundle of fascicle. - Epimysium - connective tissue sheath surrounding whole bundle of muscle. - Each skeletal muscle fibre consists of elongated muscle cell. - They contain sarcoplasm with several nuclei. Cell membrane is called sarcolemma. ### Parts of a Muscle - Flesh portion - belly, and fibrous or tendinous portion. - Fibrous portion - round muscle attaches to bone by means of tendon while membranous type of muscle attaches by aponeurosis ### Arrangement of Muscle Fibres of Skeletal Muscle - Fibres parallel to the Long Axis of the Muscle - Muscle fibres may be parallel from end to end. - e.g. strap muscle (sartorius, sternohyoid, sternothyroid) - Muscle fibres may converge to a tendon at one or both ends - e.g. Fusiform muscles like biceps brachii. - Fibres Oblique to the Long Axis of the Muscle - The muscle fibres run obliquely to the pull of the muscle. - Unipennate Muscle - Has oblique fascicles arranged on one side of the tendon, making the muscle look like a feather. E.g. Flexor pollicis longus - Bipennate Muscle - Has oblique fascicles on both sides of the tendon. Such muscle has an equal pull from both sides of the tendon. E.g. Rectus femoris - Multipennate Muscle - Muscle has many oblique fascicles arranged along several tendons in the central axis of the muscle. E.g. Deltoid muscle - Circumpennate Muscle - Muscle fibres converge from the wall of a cylindrical space to a buried tendon, like a spoke of a wheel. E.g. Tibialis anterior - In general, pennate muscles have more fascicles directly attached to a tendon than non-pennate muscles do. As a result, pennate muscles have greater power than muscles of another pattern. - Radial, Triangular or Fan-shaped Muscle - The fleshy fibres converge from a wide origin to apical insertion. E.g. temporalis, adductor longus. - Spiral-shaped Muscle - Muscles may exhibit a spiral or twisted arrangement (eg. latissimus dorsi) or may spiral around a bone (e.g. supinator). - Contains two or more plane of fibres arranged in differing directions, a type of spiral referred to as cruciate (e.g. Sternocleidomastoid). ### Classification of Skeletal Muscles according to Action - Prime mover: - A muscle is a prime mover when it is the chief muscle or member of a chief group of muscles responsible for a particular movement. - For example, the quadriceps femoris is a prime mover in the movement of extending the knee joint. - When a prime mover helps opposite action by active, controlled lengthening against gravity, it is known as action of paradox. - For example, when the hand lowers a heavy object, the extensor action of the triceps is replaced by gravity, and the movement is controlled by active lengthening of the biceps (paradoxical or eccentric action). - Antagonist: - Any muscle that opposes the action of the prime mover is an antagonist. - For example, the biceps femoris opposes the action of the quadriceps femoris when the knee joint is extended. - Fixator: - A fixator contracts isometrically (i.e., contraction increases the tone but does not in itself produce movement) to stabilize the origin of the prime mover so that it can act efficiently. - For example, the rotator cuff muscles of the shoulder joint contract as fixators while the deltoid act as prime mover. - Synergist: - In many locations in the body, the prime mover muscle crosses several joints before it reaches the joint at which its main action takes place. - To prevent unwanted movements in an intermediate joint, groups of muscles called synergists contract and stabilize the intermediate joints. - For example, the flexor and extensor muscles of the carpus contract to fix the wrist joint, and this allows the long flexor and the extensor muscles of the fingers to work efficiently. ### General Characteristics of Smooth Muscle - Involuntary but non-striated. - They form the wall of hollow viscera and tubes. - They are supplied by autonomic ground plexus. - They act to expel the contents of hollow structure. - Capable of constant motion, contract at slow speed and goes on. ### General Characteristics of Cardiac Muscle - Involuntary and striated. - Controlled by ANS and found in heart and roots of large vessels joining the heart. - Intercalated discs/ are present which serve as the site of attachment between cardiac muscle cells. - It works on steadily day with no absolute rest, yet it is flexible and capable of responding to temporary increased needs by working faster for limited period of time without being damaged. ### References - Hansen, J. and Netter, F.H. (2014) Netter's Clinical Anatomy. 3rd Edition. Saunders. Pg. 14. - Layers of the GI Tract [Accessed on https://upload.wikimedia.org/wikipedia/commons/3/31/Layers_of_the_GI_Tract_english.svg] - Mescher, A.L. & Junqueira, L.C.U. (2013) Junqueira's basic histology: text and atlas. United States: McGraw-Hill Education. Pg. 194. - Netter, F.H. (2014) Atlas of Human Anatomy. 7th Edition. Elsevier Inc.p. B Pg.8 - Patton, K.T. and Thibodeau, G.A