Skeletal System

The Skeletal System Parts of the skeletal system Bones (skeleton) Joints Cartilages Ligaments Divided into two divisions Axial skeleton- Skull and Spinal Column Appendicular skeleton- Limbs and Girdle

Functions of Bones Support of the body Gives shape Protection of soft organs Movement due to attached skeletal muscles Storage of minerals and fats- calcium, phosphate, magnesium ect… hematopoesis

Bones of the Human Body The Skeleton has 206 bones Two basic types of bone tissue Compact bone - Homogenous Spongy bone - Small needle-like pieces of bone. - Many open canals.

Compact Vs. Spongy Bone

Classification of Bones Long bones: have longitudinal axes and expanded ends. Ex. Radius/Ulna and the Femur Short: are somewhat cubelike, with their lengths and width roughly equal. Ex. Bones of the wrist and ankle Flat: are platelike structures with broad surfaces, such as ribs, scapulae, and some bones of the skull. Irregular: have a variety of shapes and are usually connected to several other bones. Ex. Vertebrae of the spinal column and many facial bones. Sesamoid: usually small and nodular and are embedded within tendons adjacent to joints. Ex. Patella

Classification of Bones on the Basis of Shape

Gross Anatomy of a Long Bone Diaphysis Shaft Epiphysis Ends Blood cells made here as adults

Structures of a Long Bone Periosteum Outside covering of the diaphysis Sharpey’s fibers Secure periosteum to underlying bone

Structures of a Long Bone Articular cartilage Covers the epiphyses Made of hyaline cartilage Decreases friction

Structures of a Long Bone Medullary cavity Cavity of the shaft Contains yellow marrow (mostly fat) in adults Contains red marrow (for blood cell formation) in infants

Bone Markings Sites of attachments for muscles, tendons, and ligaments Passages for nerves and blood vessels

Microscopic Anatomy of Bone Osteon: the fundamental functional unit of compact bone. Each osteon consists of concentric layers, or lamellae, of compact bone tissue that surround a central canal, the haversian canal. The boundary of an osteon is the cement line. Central (Haversian) canal: The haversian canal contains the bone's nerve and blood supplies. Perforating (Volkman’s) canal: Volkmann canals are any of the small channels in the bone that transmit blood vessels from the periosteum into the bone and that communicate with the Haversian canals. The perforating canals provide energy and nourishing elements for osteons.

Microscopic Anatomy of Bone

Microscopic Anatomy of Bone Lacunae: a small space containing an osteocyte in bone or chondrocyte in cartilage. Situated between the Lamella. Lacunae are connected to one another by small canals called canaliculi. Lamellae: a thin plate-like structure, often one amongst many lamellae very close to one another, with open space between.

Microscopic Anatomy of Bone Canaliculi: canals between the lacunae of ossified bone. The radiating processes of the osteocytes (called filopodia) project into these canals. Tiny canals

Changes in the Human Skeleton In embryos, the skeleton is primarily hyaline cartilage During development, much of this cartilage is replaced by bone Cartilage remains in isolated areas Bridge of the nose Parts of ribs Joints

Bone Growth Epiphyseal plates allow for growth of long bone during childhood New cartilage is continuously formed Older cartilage becomes ossified Cartilage is broken down Bone replaces cartilage

Long Bone Formation and Growth

Long Bone Formation and Growth

Bone Formation Video Bone Formation Video is embedded.

Types of Bone Cells Osteocytes Osteoblasts Osteoclasts Bone-forming cells Osteoclasts Break down bone matrix for remodeling and release of calcium Bone remodeling is a process by both osteoblasts and osteoclasts

Bone Remodeling and Modeling Video

Factors Affecting Bone Development, Growth, and Repair Deficiency of Vitamin A – retards bone development Deficiency of Vitamin C – results in fragile bones Deficiency of Vitamin D – rickets, osteomalacia Insufficient Growth Hormone – dwarfism Excessive Growth Hormone – gigantism, acromegaly Insufficient Thyroid Hormone – delays bone growth Sex Hormones – promote bone formation; stimulate ossification of epiphyseal plates Physical Stress – stimulates bone growth

Bone Fractures Types of bone fractures Closed (simple) fracture Open (compound) fracture

Common Types of Fractures

Stages in the Healing of a Bone Fracture