Anatomy 1 Skeletal System PDF

## BONES - Form most of adult skeleton. - About 206 bones - Solid living tissue - Vascularized dense connective tissue A diagram of the human skeletal system is shown. **A** shows the front of the skeletal system. **B** shows the back of the skeletal system. The bones are labeled as follows: - S...

## BONES - Form most of adult skeleton. - About 206 bones - Solid living tissue - Vascularized dense connective tissue A diagram of the human skeletal system is shown. **A** shows the front of the skeletal system. **B** shows the back of the skeletal system. The bones are labeled as follows: - Skull - Mandible - Clavicle - Scapula - Humerus - Sternum - Vertebral column - Ilium - Sacrum - Ischium - Pubis - Femur - Patella - Fibula - Tibia - Ulna - Radius - Carpus - Metacarpals - Phalanges - Tarsus - Phalanges - Metatarsals - Hip bone - Coccyx ## TYPES OF BONES: ### A- ACCORDING TO STRUCTURE: 1. **Compact Bone:** - Outer layer of flat and short bones and cylinders of long bones - Solid and compact; regularly arranged compressed bone lamellae - Arrangement corresponds to distribution of blood vessels. 2. **Cancellous (Spongy) Bone:** - Diploe of flat bones (skull) - Inner mass of short bones - Terminal ends of long bones - Thin irregularly arranged branching bone trabeculae (corresponding with lines of maximal tension), separated by bone marrow spaces ### B. ACCORDING TO SHAPE: 1. **Long Bones:** - Ex: Clavicle, humerus, radius, ulna, femur, fibula, tibia - Cylindrical in shape - Has 2 ends (upper and lower) and a shaft: - The ends (epiphysis): Have cancellous bone trabeculae covered by a shell of compact bone. - Shaft (diaphysis): Compact bone, surrounds medullary cavity. - Bone marrow: Main blood forming organ in the body - Metaphysis: Part of diaphysis near epiphysis and separated from it by epiphyseal plate of cartilage - The shaft is covered by *periosteum* (membrane covering bone), sensitive and contains blood vessels and nerves. 2. **Short Bones:** - Ex: Carpal and tarsal bones - Different forms without bone marrow - May contain red marrow in interstitial spaces; in-between the trabeculae. 3. **Sesamoid Bones:** - Ex: *Patella*; the largest sesamoid bone. - Special variety of short bones present in certain sites in the body - Invested in tendons of some muscles - Act to modify pressure and diminish friction at their origin. 4. **Short Long Bones:** - Ex: Metacarpal, metatarsal and phalanges - Short cylindrical with one end and bone marrow cavity 5. **Flat Bones:** - Ex: Vault of the skull, ribs, scapula - Thin and broad bones - Outer and inner plates of compact bones with an intermediate cancellous bone 6. **Irregular Bones:** - Ex: Vertebrae, hip bones - Ill-defined shape due to presence of bony processes and extensions diverge in different directions. 7. **Pneumatic Bones:** - Ex: Paranasal sinuses; found in some bones of face and around the nose (contain small air cavities inside them). - They are: 1. Maxillary air sinuses 2. Frontal air sinuses 3. Sphenoid air sinuses 4. Ethmoid air sinuses ### C. ACCORDING TO TYPE OF OSSIFICATION: 1. **Cartilaginous Ossification:** - Cartilage is changed to bone. - Ex: Long bones 2. **Intra-membranous Ossification:** - Membrane is changed to bone. - Ex: Flat bones - Growth in thickness (sub-periosteal deposition of bone) ## BONE MARROW: - **Red bone marrow:** - Forms red blood cells. - Lies in: Skull, vertebrae, ribs, sternum, hip, upper end of humerus, femur. - **Yellow (inert) bone marrow:** - Is composed of fatty tissue. ## FUNCTIONS OF BONES: 1. Give the body its form, contour and define its width. 2. Support overlying soft tissue. 3. Protect important, delicate and fragile internal organs; skull for brain, vertebrae for spinal cord and scapula and ribs for heart and lungs. 4. Give areas for muscular attachment. 5. Act as levers during movements. 6. Help the body to assume different positions such as standing up, sitting down... 7. Essential in walking, running, jumping, playing, up stairs... 8. Stores for calcium salt to time of need such as pregnancy and aging 9. Production of R.B.Cs. via bone marrow ## BLOOD SUPPLY OF BONES: 1. **Nutrient artery:** Bone marrow, branches in metaphysis (its branches are end arteries). 2. **Epiphyseal artery:** Epiphysis 3. **Metaphyseal artery:** Metaphysis 4. **Periosteal artery:** Periosteum. **N.B:** Cartilaginous epiphysis hyaline cartilage has NO blood supply. As ossification begins, blood vessels penetrate epiphyseal ossification centres. ## CARTILAGINOUS OSSIFICATION: Pre-existing hyaline cartilage model of bone is gradually destroyed and replaced by bone. **Steps of cartilaginous ossification:** 1. Each bone is represented by small cartilaginous moulds in embryo. 2. Primary centre of ossification appears in shaft of the cartilage during intra uterine life. 3. Secondary centres of ossification appear at the end of long bone epiphysis around birth. 4. Bone occupied whole cartilaginous mould except at epiphyseal plate of cartilage. ## So, the long bone is composed of: - a. Shaft (diaphysis) - b. Two ends (epiphysis) - c. Epiphyseal plate of cartilage - d. Metaphysis **AT puberty (14 – 16 years) adolescent:** - One epiphyseal plate ossifies and unites with the shaft (non-growing end). **At adult age (18-21 years):** - Other epiphyseal plate ossifies (growing end). - No further growth in length later ## Regional Classification of Bones: | Region of Skeleton | Number of Bones | |---------------------------------|-----------------| | Axial skeleton | | | Skull | | | Cranium | 8 | | Face | 14 | | Auditory ossicles | 6 | | Hyoid | 1 | | Vertebrae (including sacrum and coccyx) | 26 | | Sternum | 1 | | Ribs | 24 | | Appendicular skeleton | | | Shoulder girdles | | | Clavicle | 2 | | Scapula | 2 | A diagram of the human skeletal system is shown with labels, showing anterior and posterior views. The axial and appendicular skeleton are labeled and highlighted in different colors. The following bones are labelled: - Cranium - Cervical Vertebrae - Clavicle - Scapula - Costal Cartilage - Sternum - Humerus - Ribs - Radius - Ulna - Carpus - Metacarpals - Phalanges - Hyoid bone - Costal margins - Pelvic girdle - Sacrum - Coccyx - Pubic symphysis - Hip bone - Femur - Patella - Tibia - Fibula - Tarsus (tarsal bones) - Metatarsals - Phalanges ## Upper extremities: | Bone | Number | |-------------|--------| | Humerus | 2 | | Radius | 2 | | Ulna | 2 | | Carpals | 16 | | Metacarpals | 10 | | Phalanges | 28 | ## Pelvic girdle: | Bone | Number | |-----------|--------| | Hip bone | 2 | ## Lower extremities: | Bone | Number | |----------|--------| | Femur | 2 | | Patella | 2 | | Fibula | 2 | | Tibia | 2 | | Tarsals | 14 | | Metatarsals | 10 | | Phalanges | 28 | Total: **206** ## Bone Markings and Formations: - Bone markings appear wherever tendons, ligaments, and fasciae are attached or where arteries lie adjacent to or enter bones. - Other formations occur in relation to the passage of a tendon (often to direct tendon or improve its leverage) or to control type of movement occurring at a joint. **The various markings and features of bones are:** - **Capitulum:** small, round, articular head (capitulum of humerus) - **Condyle:** rounded, knuckle-like articular area, usually occurring in pairs (lateral femoral condyle) - **Crest:** ridge of bone (iliac crest) - **Epicondyle:** eminence superior to a condyle (lateral epicondyle of the humerus) - **Facet:** smooth flat area, usually covered with cartilage, where a bone articulates with another bone (superior costal facet on the body of a vertebra for articulation with a rib) - **Foramen:** passage through a bone (obturator foramen) - **Fossa:** hollow or depressed area (infraspinous fossa of scapula) - **Groove:** elongated depression or furrow (radial groove of the humerus) - **Head (L. caput):** large, round articular end (head of the humerus) A diagram of the human skeleton is shown, showing the location of various bone markings. The following structures are labeled: - Superior articular facet - Spinous process of T6 - Right posterolateral 7th rib - Capitulum of humerus - Trochlea of humerus - Superior costal facet - Articular facet for tubercle of 6th rib - Crest of head - Vertebral body - Calvaria of cranium - External occipital protuberance - Spine of scapula - Head of humerus - Greater tubercle of humerus - Infraspinous fossa of scapula - Radial groove of humerus - Spinous processes of vertebrae - Lateral epicondyle of humerus - Iliac crest - Greater sciatic notch - Greater trochanter of femur - Ischial tuberosity - Obturator foramen - Lateral femoral condyle - Soleal line of tibia - Lateral malleolus of fibula