Skeletal system: BONE & CARTILAGE Bpharm semester I lecture 2 Dr Abubakr H Mossa Sr. Instructor Anatomy 3/10/12

Lecture outline: Parts of skeletal system (skeleton): Bone: Axial Appendicular Bone: Bone as a living tissue Composition of bone Functions of bone Types of bone tissue Ossification: bone formation Bones classification Cartilage: composition and types

Skeletal system Parts of Skeletal system: Bone (skeleton): Cartilage Axial Appendicular Cartilage Joints

Skeleton The skeleton has two parts: the axial skeleton and the appendicular skeleton. The axial skeleton includes the: skull, the hyoid bone, the vertebral column (spine, sacrum, and coccyx), the sternum the ribs. Its components are aligned along the long axis of the body.

Skeleton The appendicular skeleton includes the bones of the: Upper extremities: Arm: humerus Forearm: radius & ulna Hand: carpals (8), metacarpals (5) & phalanges (14) The pectoral (shoulder) girdle: clavicle & scapula The pelvic girdle: hip bone bones of the lower extremities: Thigh: femur ( in the knee :patella) Leg: tibia & fibula Foot: tarsals (7), metatarsals (5) & phalanges (14) Its components are outside the body main axis.

Bone Bone as a living tissue: It has blood vessels and nerves. Self repairing Constantly remodeled

Bone Functions of bone: Supporting framework necessary for movement Protection of internal organs Calcium and phosphate store Site of formation of blood (red bone marrow) in the marrow cavity. In adult the red marrow is restricted to the bones of skull, vertebrae, sternum, ribs, shoulder girdle, hip and the proximal ends of the long bone. What happens to the red marrow in the shaft of the long bones in adult?

Bone tissue Types of bone tissue: Initially all bones are woven but later on they differentiate into two main types: Compact bone: hard and heavy, forms the outer layer (cortex) of all bones Cancellous (spongy): lighter and found in the ends of long bones and in the irregular bones

Bone: Composition of bone: Cells Intercellular matrix: Collagen fibers Inorganic crystals (Calcium salts)

Bone Ossification: bone formation Bone develops from embryonic connective tissue which differentiate (ossify) in two ways: Endochondral (cartilage replacing) ossification: a model of cartilage is replaced by bone. Intramembranous (dermal) ossification: ossification starts directly in a membrane of connective tissue (without a preceding cartilage model) Compare the two types of ossification with respect to the following: Mechanism Duration Bones formed by each mechanism

Bone Classification: Axial or appendicular According to the shape; Long and short limb bones Flat and irregular axial bones Pneumatic bones (of skull) Sesamoid bones

Bone Long bone: Parts: Formed by endochondral ossification Shaft (diaphysis): cortex of compact bone and marrow cavity inside. Ends (epiphysis): thin shell of compact bone and interior of spongy bone Junction between the two called metaphysis Formed by endochondral ossification

Bone Short bones: Flat bones: Carpal and tarsal bones of the wrist and the foot, respectively. Flat bones: Has two layers of compact bone : inner and outer table Diploe: layer of spongy bone between the two tables Develops as dermal bone Irregular bones: vertebrae, hip and basal cranial bone Pneumatic bone: cranial bones in which air sinuses are found (maxilla, sphenoid ..) Sesamoid bone: A bone develops within a tendon when it rubs against a bony surface. Patella of the knee

Cartilage: Composition: Types: Cells called chondrocytes matrix : consists of fibers & semi-rigid ground substance Types: Hyaline: found in costal cartilages, epiphyseal plates (important for growth) & articular cartilage Fibrocartilage: as in the intervertebral discs Elastic cartilage: forms the cartilage of ear & nose

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