Skeletal System Dr. Lubna Nazli 1

Objectives 2 Components Functions of bone Number of bones Bone types Bone structure Bone classification Bone ossification Axial skeleton Appendicular skeleton Applied aspects

Skeletal System Composed of the body’s bones and associated ligaments, tendons, and cartilages. The human skeleton consists of 206 bones. We are actually born with more bones (about 300), but many fuse together as a child grows up. These bones support your body and allow us to move. 3

4

The longest bone in our body is the femur (thigh bone). The smallest bone is the stapes bone inside the middle ear. 5

Functions of bone Bones function in: Support of soft tissues Movement Protection Mineral homeostasis - calcium and phosphate Blood cell production - red marrow 6

Types of Bone Cancellous / spongy Found in marrow cavity No Haversian systems Surface lined by endosteum Compact Forms the dense shell of bones Has Haversian systems Outer surface lined by periosteum Inner surface lined by endosteum 7

Compact and Spongy Bone Tissue Organization Bones of the skeleton contain a combination of both types of bone tissue organization. Compact bone – dense outer layer Spongy bone – honeycomb of trabeculae filled with yellow bone marrow 8

Anatomy of a Typical Long Bone 9

Bone structure Dense outer layer of compact bone. Internal spongy (cancellous) bone Long bones have internal marrow cavity 10

Bone Classification by Shape 11

Classification of Bones: By Shape Long bones – longer than they are wide (e.g., humerus, femur, ulna, radius, tibia & fibula) 12

Flat bones – thin, flattened, and a bit curved (e.g.,sternum, ribs and most skull bones) 13

Short bones Cube-shaped bones of the wrist and ankle Eg: carpals & tarsal bones 14

Sesamoid bones Bones that form within tendons. (e.g., patella) 15

Irregular bones – bones with complicated shapes (e.g: vertebrae and hip bones) 16

Bone structure Typical long bone structure: articular cartilage epiphyses (ends) Spongy bone diaphysis (shaft) Compact bone Metaphysis periosteum medullary (marrow) cavity endosteum 17

Bone is covered by a double-layered membrane known as the periosteum. It has an outer fibrous layer of dense irregular connective tissue. Inner cellular layer contains osteoprogenitor cells and osteoblasts. 18

Periosteum is richly supplied with nerve fibers, lymphatic vessels and blood vessels. These enter the bone of the shaft via a nutrient foramen. Periosteum is connected to the bone matrix via strong strands of collagen.(SHARPEY’S fibers.) 19

Structure of short, flat and irregular bones outer thin plates of periosteum covered compact bone inner endosteum covered spongy bone 20

Bone ossification Membranous ossification Cartilaginous ossification 21

The skeleton has two parts: the axial skeleton the appendicular skeleton. The axial skeleton includes the skull, the hyoid bone, the vertebral column (spine, sacrum, and coccyx), the sternum, and the ribs. Its components are aligned along the long axis of the body. 22

The appendicular skeleton includes bones of the upper extremities (arms, forearms, and hands), the pectoral (shoulder) girdle, the pelvic (hip) girdle, the bones of the lower extremities (thigh, knee, leg, and foot). Its components are outside the body main axis. 23

24

25

The Appendicular Skeleton 1.Pectoral girdle 2.Upper limbs 3.Pelvic girdle 4.Male and Female pelvis 5.Lower limbs

27

Vertebral Column Cervical – In neck region Thoracic – Posterior to thoracic cavity Lumbar – Support lower back Sacrum – Five fused sacral vertebrae Coccyx – Four fused coccygeal vertebrae 28

Vertebral Regions Cervical – Neck C1-C7 Thoracic – Articulate with ribs T1-T12 Lumbar – Largest and strongest L1-L5 Sacrum – Triangular bone – 5 fused sacral vertebrae Coccyx – Small triangular bone – Usually 4 fused coccygeal vertebrae 29

30

31

Abnormal Curvatures Scoliosis – An abnormal lateral curvature of the spinal column – Curvature can occur in an “S” or “C” deviation 32

Kyphosis – An exaggerated dorsal curvature in the dorsal region – Common is aged individuals because of osteoporosis 33

Lordosis – Accentuated lumbar curvature – Being overweight or pregnant causes an excessive load up front 34

Interesting medical facts related to skeletal system! Estimating the age and sex of individual. In suspicious death the cause of death is known by forensic experts using bones. Bone grafts in reconstruction and repair. Bone injuries and their complications. 35

Applied anatomy Fractures Avascular necrosis Osteoporosis Infections Bone marrow transplantation 36

SDL To familiarise with terms describing the features of bones ( condyle, facet, tubercle) What is growing end of the bone? Its importance. 37