Skeletal System Reading Material 2025 PDF

ANATOMY PHYSIOLOGY SKELETAL SYSTEM  Support Protection Movements Storage Blood Cell Production  206 bones in the adult skeletal system. 98 75 percent of body’s total percent of body’s total cal...

ANATOMY PHYSIOLOGY SKELETAL SYSTEM  Support Protection Movements Storage Blood Cell Production  206 bones in the adult skeletal system. 98 75 percent of body’s total percent of body’s total calcium is in the bones phosphorus is in the bones  HISTOLOGY Connective Tissues of the Skeletal System: Bone Cartilage Tendon Ligaments  HISTOLOGY CONNECTIVE TISSUE - consist of long fibers embedded in noncellular matter (ground substance) FUNCTIONS: - Supports and connects internal organs - Forms bones and walls of blood vessels - Attaches muscles to bones - Replaces tissues of other types following injury.  HISTOLOGY Extracellular Matrix – Intercellular substance of a tissue. 1. Collagen 2. Ground Substance - the gel-like material in which connective tissue cells and fibers are embedded. Proteoglycan – large molecules consisting of polysaccharides attached to core proteins.  HISTOLOGY Extracellular Matrix – Intercellular substance of a tissue. 1. Collagen - Tough, ropelike proteins. FIBROBLASTS - immature fiber-producing cells of connective tissue - Chondroblast - Collagenoblast - Osteoblast  HISTOLOGY Extracellular Matrix – Intercellular substance of a tissue. 2. Ground Substance - the gel-like material in which connective tissue cells and fibers are embedded. Proteoglycan – large molecules consisting of polysaccharides attached to core proteins.  HISTOLOGY Connective Tissues of the Skeletal System: Bone Cartilage Tendon Ligament  BONE CARTILAGE Strong and rigid form Firm and flexible form of connective tissue. Can not be bent Can be bent Matrix – Collagen and Hydroxyapatite Matrix – Collagen and proteoglycans (calcium and phosphate crystals) Osteoblasts Chondroblasts Contains blood vessels No blood vessels Provide skeletal support and shape Provide flexibility to the body and to the body smoothen bone surfaces Form the skeleton Found in the ear, nose, larynx, trachea, ribs, and joints.  HISTOLOGY TENDON A band of strong white fibrous tissue that connects a muscle to a bone.  HISTOLOGY LIGAMENT A band of fibrous tissue connecting bones or cartilages serving to support and strengthen joints.  GENERAL FEATURES OF BONE Long Bones Short Bones Flat Bones Irregular Bones Sesamoid Bones – ovoid, nodular bones embedded within a tendon or joint capsule STRUCTURE OF LONG BONES  DIAPHYSIS The shaft portion of the long bones. The primary site of ossification.  EPIPHYSIS The expanded end portion of the long bones. The secondary site of ossification.  METAPHYSIS The growth zone between the epiphysis and diaphysis. The area of greatest metabolic activity in a bone. EPIPHYSEAL GROWTH PLATE The thin plate of cartilage between the epiphysis and the shaft of a long bone. The site of growth in length and is obliterated by epiphyseal closure.  BONE TISSUES Compact Bone Spongy Bone  COMPACT BONE Composition of bone tissues on the outer portion of the bone. OSTEONS The basic unit of structure of compact bone. Central/Haversian Canal + Concentrically arranged lamellae. HAVERSIAN CANAL Tubes or canals that allows the passage of blood vessels and nerves fibers. VOLKMANN’S CANAL Connects Haversian Canals to each other Run parallel to the long axis of the bone  CANCELLOUS/SPONGY BONE Consists of delicate interconnecting rods or plates of bones called the TRABECULAE Spaces are filled with bone marrow Usually located in the epiphyses of long bones. Adds strength without the added weight. OSTEOPOROSIS  ARTICULAR CARTILAGE The smooth, white tissue that covers the ends of bones where they come together to form joints.  PERIOSTEUM Fibrous membrane covering the outer portion of the bone. Contains nerves and blood vessels. This is the portion of the bone that can detect pain.  MEDULLARY CANAL Inner portion of the bone. Bone marrow is located within the medullary canal. RED BONE MARROW YELLOW BONE MARROW RED BONE MARROW Consists of blood-forming cells The only site of blood formation in adults The site of ERYTHROPOEISIS YELLOW BONE MARROW Consists of adipose tissues (fats)  ENDOSTEUM Thin membrane lining the medullary cavity. BONE CELLS BONE CELLS OSTEOGENIC CELLS Mitotically active stem cell Differentiates into osteoblasts OSTEOBLASTS Bone forming cells that secrete bone matrix (Collagen and Calcium-Binding Proteins) OSTEOCYTES Mature bone cells Monitor and maintain the bone matrix Act as stress "sensors" and respond to mechanical stimuli OSTEOCLASTS Large, multi-nucleated cells that resorb or breakdown bone matrix BONE REMODELLING  BONE REMODELLING Continuing process of synthesis and destruction that gives bone its mature structure and, maintains normal calcium levels in the body OSSIFICATION  OSSIFICATION Formation of bone by osteoblasts. After an osteoblast becomes completely surrounded by bone matrix, it becomes a mature bone cell, or osteocyte.  OSSIFICATION Bone formation that occurs within connective tissue membranes is called intramembranous ossification. bone formation that occurs inside cartilage is called endochondral ossification  INTRAMEMBRANOUS OSSIFICATION Osteoblasts produce bone in connective tissue membranes. Occurs in the bones of the skull. ENDOCHONDRAL OSSIFICATION EPIPHYSEAL PLATE Synthesis of new cartilage Calcification of the cartilage Cartilage to Bone Synthesis of another set of cartilage Calcification of the cartilage BONE GROWTH  BONE REMODELLING Involves the removal of existing bone by osteoclasts and the deposition of new bone by osteoblasts Remodeling is responsible for changes in bone shape, the adjustment of bone to stress, bone repair, and calcium ion regulation in the body fluids HUMAN ANATOMY AND PHYSIOLOGY BONES OF THE HUMAN BODY Dr. Nasser A. Jawadil AXIAL SKELETON The axial skeleton is composed of the skull, the vertebral column, and the thoracic cage. SKULL  skull The 22 bones of the skull are divided into those of the braincase (neurocranium/ cranium) and those of the face BRAINCASE (neurocranium) Encloses the cranial cavity Consists of 8 bones Surround and protect the brain FACIAL BONES (viscerocranium) Form the structure of the face 14 facial bones The mandible is the only freely movable bone in the skull.  skull The Cranial Bones are: Parietal Temporal Frontal Occipital Sphenoid Ethmoid  skull The Facial Bones are: Maxilla Zygomatic Palatine Nasal Lacrimal Inferior Nasal Concha Mandible Vomer Anterior View Frontal Bone Nasal Bone Zygoma Maxilla Mandible Lateral View Parietal Bone Frontal Bone Sphenoid Bone Occipital Bone Maxillary Bone Temporal Bone Mandible Superior View Frontal Bone Parietal Bone Occipital Bone Posterior View Parietal Bone Occipital Bone Temporal Bone Mandible  skull SUTURES These are fibrous joints connecting the bones of the skull. The main sutures of the skull are: (1) Coronal Suture (2) Sagittal Suture (3) Lambdoid Suture (4) Squamous Suture To the untrained eye, they may look like fractures. Superior View Coronal Suture Sagittal Suture Connects the frontal and parietal bones Connects the two parietal bones Lambdoid Suture Connects the occipital and parietal bones Posterior View Sagittal Suture Connects the Lambdoid two parietal Suture bones Connects the occipital and parietal bones Lateral View Coronal Suture Lambdoid Suture Connects the Connects the frontal and occipital and parietal bones parietal bones Squamous Suture Connects the parietal and temporal bones Lateral View PTERION This is the area where the frontal, parietal, sphenoid, and temporal bones unite. This is the weakest spot of the skull. Injury in this area could lead to epidural hematoma  The pterion overlies the Middle Meningeal Artery. A fracture in the pterion can damage and rupture this artery, which will lead to bleeding within the skull. This is the superior view of the skull when the roof of the skull is removed. This is called the Floor of the Skull.  Frontal Bone Ethmoid Bone Sphenoid Bone Temporal Bone Parietal Bone Occipital Bone  Frontal Sinus The sphenoid bone is a Sphenoid Bone butterfly-shaped bone that extends deep within the skull. This is the largest opening in Foramen Magnum the skull. This is where the spinal cord joins the brain.  The central region of the sphenoid bone is modified into Sella Turcica a structure resembling a saddle, the sella turcica, which contains the pituitary gland. Inferior View  Hard Palate Vomer Carotid Canal Mastoid Process Anterior View Middle Nasal Concha Inferior Nasal Concha The superior and middle concha are part of the ethmoid The inferior nasal bone conchae is a separate bone, one in each side of the nose.  Superior Nasal Concha Middle Nasal Concha Inferior Nasal Concha The nasal conchae (singular: concha) or nasal turbinate are bony structures located on each lateral wall of the nasal cavity. The nasal conchae increase the surface area of the nasal cavity. Lateral View  Anterior View The conchae are in green. Meatus means “opening” Anterior View Perpendicular Plate of Ethmoid Bone Nasal Septum Vomer  NASAL SEPTUM Divides the nasal cavity into right and left halves. Two bones form the septum (“wall”) – the Perpendicular Plate of the Ethmoid and the Vomer. Anteriorly, the nasal septum is consist of a hyaline type of cartilage.  PARANASAL SINUSES Several of the bones associated with the nasal cavity have large cavities within them, called the paranasal sinuses which open into the nasal cavity. The sinuses decrease the weight of the skull and act as resonating chambers during voice production. Anterior View Maxilla The maxilla forms the upper jaw, and the mandible forms the lower jaw. Mandible  The alveolar sockets in our mandible ALVEOLAR BONE Our upper set of teeth sits in the alveolar bone of the maxilla, and our lower set of teeth sits in the alveolar bone of the mandible. Each tooth has its own socket called the alveolar socket. The bone surrounding the teeth is called the alveolar bone. Anterior View The orbits are cone-shaped fossae, so named because the eyes rotate within them. Fossae means a hollow or shallow depression. Orbit The bones of the orbits provide both protection for the eyes and attachment points for the muscles that move the eyes Anterior View Major bones that form the orbit include: Frontal Bone Frontal Bone (superior boundary) Lacrimal Bone Lacrimal Bone (medial boundary) Zygomatic Bone (lateral and inferior boundaries) Zygomatic Bone Maxillary Bone (inferior and medial boundaries) Maxillary Bone  Auditory Ossicles These paired bones are located in the middle ear, and are the smallest bones in the human body. The auditory ossicles form a flexible, bony bridge that transmits vibrations from the tympanic membrane (eardrum). Actual sizes of the auditory ossicles. The stapes is the smallest bone in the human body.  Hyoid Bone The hyoid bone is an unpaired, U-shaped bone. It is not part of the skull and has no direct bony attachment to the skull or any other bone. This is the only bone in the human body that is not attached to a bone. It serves as an attachment for some tongue muscles and muscles in the neck. Strangulation injury will result to a fracture of the hyoid bone. The hyoid bone is the only “floating” bone in the human body. VERTERBRA  Vertebral Column The vertebral column, or spine, is the central axis of the skeleton, extending from the base of the skull to slightly past the end of the pelvis. Consists of 26 individual bones, grouped into five regions: Cervical 7 Thoracic 12 Lumbar 5 Sacrum 1 Coccyx 1  Vertebral Foramen This is where the spinal cord is located, protected in all sides. Lamina Vertebral Arch Pedicle The two vertebral arches in each side will form the Vertebral Body vertebral foramen The weight-bearing portion of the vertebra  Spinous Process Transverse Process Transverse Process In skeletal anatomy, a “process” mean a projection from a structure. The spinous process can be felt at the back, especially in thin individuals.  The intervertebral disks are made up of fibrous cartilage, and serves primarily to allow movement between adjacent vertebral bodies, to absorb shock, and to transmit loads through the vertebral column  Cervical Vertebrae The first cervical vertebra (C1) is called the Atlas. The second cervical vertebra (C2) is called the Axis. Note that the Atlas has no vertebral body. Nodding or “YES” movement is done by the Atlas. The dens of the Axis articulates with the Atlas. Shaking your head such as in “NO” movement is due to the Axis.  Thoracic Vertebrae They possess long, thin spinous processes that are directed inferiorly. Note the long spinous processes that are directed inferiorly. The thoracic vertebra is also unique since it also articulates with the ribs.  Lumbar Vertebrae They have large, thick bodies and heavy, rectangular transverse and spinous processes. The lumbar vertebrae carry a large amount of body weight, hence they have massive bodies.  Sacrum The five sacral vertebrae are fused into a single bone called the sacrum 1 2 SACRUM 3 4 5 COCCYX  Coccyx The coccyx, or tailbone, usually consists of four more-or-less fused vertebrae. The coccyx is easily fractured when a person falls by sitting down hard on a solid surface or in women during childbirth. SACRUM 1 2 3 COCCYX 4 RIBS  Rib Cage The rib cage protects the vital organs within the thorax and prevents the collapse of the thorax during respiration. It consists of the thoracic vertebrae, the ribs with their associated cartilages, and the sternum.  Clavicle Manubrium Ribs Sternum Body (breastbone) Xiphoid Costal Cartilages Process  1 2 3 4 TRUE RIBS 5 Ribs 1-7 6 Attach directly to the sternum by means 7 of costal cartilages. 11 8 12 9 10  1 2 3 4 FALSE RIBS 5 Ribs 8-12 6 7 Do not attach directly to the sternum 11 8 12 9 10  1 2 3 4 Ribs 8,9, and 10 5 6 Attach to the sternum by a common costal 7 cartilage 11 8 12 9 10 Common Costal Cartilage  1 2 3 4 5 Ribs 11 and 12 6 Do not attach at all to the sternum and are 7 called floating ribs. 11 8 12 9 10  APPENDICULAR SKELETON The appendicular skeleton consists of the bones of the upper and lower limbs, as well as the girdles, which attach the limbs to the axial skeleton. UPPER LIMBS  Pectoral Girdle The pectoral girdle, or shoulder girdle , consists of four bones, two scapulae and two clavicles, which attach the upper limb to the body.  Scapula The scapula, or shoulder blade, is a flat, triangular bone with three large fossae (“shallow depression”) where muscles extending to the arm are attached. A fourth fossa, the glenoid cavity, is where the head of the humerus connects to the scapula. A ridge, called the spine, runs across the posterior surface of the scapula. A projection, called the acromion process, extends from the scapular spine to form the point of the shoulder. Acromion Process Coracoid Process Glenoid Cavity Subscapular Fossa This is where the head of the humerus articulates Medial Border Anterior View  Acromion Process Supraspinous Fossa Glenoid Cavity Spine of the Scapula Infraspinous Fossa Tip: If you see the spine of the scapula, you are looking at the scapula Posterior View posteriorly.  Upper Limb The upper limb consists of the bones of the arm, forearm, wrist, and hand The humerus is the only bone in the arm. Humerus The proximal end of the humerus has a smooth, rounded head, which attaches the humerus to the scapula at the glenoid cavity. Around the edge of the humeral head is the anatomical neck. This is the area where the humerus grows in length. When the joint needs to be surgically replaced, a more accessible site for surgical removal is at the surgical neck, located at the proximal end of the humeral shaft.  There are two bones in the forearm, the radius and ulna Radius Ulna Tip: The radius is in your “thumb” side. The olecranon of the Ulna is a prominent bone in our elbow. The wrist is composed of 8 carpal bones. The hand is made up of the metacarpals and phalanges  The metacarpals form the bones in the palm/dorsum of the hand. Metacarpal heads The knuckles in your fist are formed by the heads of the metacarpals Note that the thumb has only the proximal and distal phalanges. LOWER LIMBS  Pelvic Girdle The pelvic girdle is the place where the lower limbs attach to the body.  Sacrum Pelvic Girdle Hip Bones The right and left hip bones join each other anteriorly and the sacrum posteriorly to form a ring of bone called the Pelvic Girdle.  Sacrum Coccyx Pelvis Hip Bones PELVIC GIRDLE = Sacrum + Hip Bones PELVIS = Sacrum + Hip Bones + Coccyx Note that although the sacrum and coccyx will form the pelvis, the sacrum and coccyx are still part of the vertebral column, hence the axial skeleton.  There are two hip bones, one on each side. Each hip bone is formed by three bones fused to one another to form a single bone. These bones are Ilium, Ischium, and Pubis Lateral View Acetabulum Lateral View The acetabulum is the socket in the hip bones where the femoral attaches to the pelvis.  The femur is the only bone in the thigh. It is the longest, heaviest, and strongest bone in Femur the human body. In everyday terms, a “broken hip” is usually a break of the femoral neck. The patella or kneecap is the largest sesamoid bone in the human body. It forms the knee bone. A sesamoid bone is a small round bone that is imbedded within a tendon, whose purpose is to Patella reinforce and decrease stress on that tendon  There are two bones in the leg, the tibia and fibula. The fibula is located laterally (think FIBULAteral) Tibia is the larger bone and carries the weight of Fibula Tibia the body. Fibula is the thinner bone. (Think Tibia=Taba, Fibula=Fayat) These two malleoli are prominent landmarks in the ankle joint. Lateral Malleolus Medial Malleolus (Fibula) (Tibia) Lateral Malleolus (Fibula)  1. Talus 5. Medial Cuneiform 2. Calcaneus 6. Intermediate Cuneiform There are seven tarsal bones: 3. Cuboid 7. Lateral Cuneiform 4. Navicular  1 – Medial Cuneiform 2 – Intermediate Cuneiform Lateral Side 3 2 3 – Lateral Cuneiform 1 Just like the thumb, the great toe (“hallux”) only has the proximal and distal phalanges END  BONE ANATOMY 206 bones in an average adult.  BONES OF THE SKULL Total bones = 22 Braincase/Cranium/Neurocranium = 8 bones - encloses the cranial cavity - surround and protect the brain Facial Bones = 14 bones - form the structure of the face  BONES OF THE SKULL HYOID BONE Unpaired, U-shaped bone Not part of the skull No direct bony attachment FUNCTION: Provides an attachment for some tongue muscles Attachment point for neck muscles that elevate the larynx during speech or swallowing.  VERTEBRAL COLUMN “Backbone” The central axis of the skeleton Extends from the base of the skull to slightly past the end of the pelvis. 26 individual bones Cervical vertebrae – 7 Thoracic vertebrae – 12 Lumbar vertebrae – 5 Sacral bone – 1 Coccyx bone – 1  VERTEBRAL COLUMN PRIMARY CURVATURES Thoracic and sacral (pelvic) curves. Begin to develop soon after birth SECONDARY CURVATURES Cervical curve – as the children begin to raise their head and sit. Lumbar curve – develops when the children learn to walk. Inferior curves (lumbar and sacral) – more pronounced in women.  VERTEBRAL COLUMN CURVATURES Cervical region – curves anteriorly Thoracic region – curves posteriorly Lumbar region – curves anteriorly Sacral and coccygeal regions – curve posteriorly GENERAL PLAN OF THE VERTEBRAE BODY The weight-bearing portion. VERTEBRAL ARCH consists of laminae and pedicles. TRANSVERSE PROCESS extends laterally from each side of the arch, between the pedicle and lamina. SPINOUS PROCESS projects dorsally from where the two laminae meet. GENERAL PLAN OF THE VERTEBRAE VERTEBRAL FORAMEN The vertebral foramina of all the vertebrae form the vertebral canal where the spinal cord is located. Transverse and Spinous Processes They serve as point of attachments for muscles that move the backbone. GENERAL PLAN OF THE VERTEBRAE INTERVERTEBRAL FORAMINA Formed by notches in the pedicles of adjacent vertebrae. This is where the spinal nerves exist. INTERVERTEBRAL DISKS Formed by fibrocartilage. Separates the vertebral bodies.  RIB CAGE Protects the organs within the thorax Prevents the collapse of the thorax during respiration. Consists of: 1. Thoracic vertebrae 2. Ribs with their cartilages 3. Sternum  RIBS 12 pairs Divided into true ribs and false ribs TRUE RIBS – Ribs 1 to 7 FALSE RIBS – Ribs 8 to 12 Floating Ribs – Ribs 11 and 12  STERNUM “Breastbone” Three parts: Manubrium Body Xiphoid Process  STERNUM Jugular Notch - located between the ends of the clavicles where they articulate with the sternum. Sternal Angle - junction of the manubrium and the body of the sternum - identifies the location of the second rib, allowing the rib to be counted. APPENDICULAR SKELETON  APPENDICULAR SKELETON Consists of: Pectoral/Shoulder Girdle Pelvic Girdle Upper Limbs Lower Limbs  PECTORAL GIRDLE Attach the upper limbs to the body. Consists of: Scapula Clavicle  SCAPULA “Should Blade” Flat, triangular bone Glenoid Fossa - where the head of the humerus connects to the scapula. Acromion Process - form the point of the shoulder.  CLAVICLE “Collarbone” Articulates with the scapula at the acromion process. The proximal end of the clavicle is attached to the sternum, providing the only bony attachment of the scapula to the remainder of the skeleton. First to begin ossification in the fetus, but the last to complete.  UPPER LIMB Consists of: Arm Forearm Wrist Hand  ARM It contains the HUMERUS. The proximal end of the humerus has a smooth, rounded head, which attaches the humerus to the scapula at the glenoid cavity. Greater and Lesser Tubercles – for attachment of muscles from scapula and hold the humerus to the scapula. Deltoid Tuberosity – attachment for the deltoid muscle. Epicondyles – provide attachment sites for forearm muscles.  FOREARM Has two bones: Ulna (medial or little finger side) Radius (lateral or thumb side)  ULNA The proximal end of the ulna forms a trochlear notch that fits tightly over the end of the humerus, forming most of the elbow joint. Just proximal to the trochlear notch is an extension of the ulna, called the olecranon (elbow) process, which can be felt as the point of the elbow Just distal to the trochlear notch is a coronoid process, which helps complete the “grip” of the ulna on the distal end of the humerus.