Anatomy: bones and functions

periosteum

a dense layer of vascular connective tissue that surrounds the bones, providing nourishment and serving as an attachment point for tendons and ligaments.

diaphysis

the elongated shaft of a long bone, providing structural support and containing the medullary cavity.

epiphysis

the end part of a long bone, comprised of spongy bone and covered by articular cartilage, where bone growth occurs and joints are formed.

articular cartilage

a smooth, slippery tissue that covers the ends of bones at joints, facilitating movement and reducing friction during articulation.

periosteum

a dense layer of vascular connective tissue that surrounds the bones, providing nourishment and serving as an attachment point for tendons and ligaments.

endosteum

a thin, vascular membrane that lines the inner surface of the medullary cavity and the trabeculae of spongy bone, playing a crucial role in bone growth, repair, and remodeling.

spongey bone

also known as cancellous bone, it is a porous, less dense bone tissue characterized by a network of trabeculae (bars and plates of bone) that provide strength and house red bone marrow for hematopoiesis.

compact bone

it is a dense, hard bone tissue that forms the outer layer of all bones and the diaphysis of long bones, providing strong structural support and protection.

epiphyseal plate

a hyaline cartilage plate in the metaphysis at each end of a long bone, responsible for longitudinal bone growth during childhood and adolescence, often referred to as the growth plate.

partial fracture/greenstick fracute

a fracture in which the bone cracks but does not break all the way through; common in children due to their more flexible bones, resembling a green stick bending and breaking partially.

transverse fracture

a fracture that occurs straight across the bone, perpendicular to the long axis of the bone, typically caused by a direct blow or pathological weakening of the bone.

oblique fracture

a fracture that occurs at an angle to the long axis of the bone, usually resulting from a twisting force or impact causing a diagonal break.

compound fracture

also known as an open fracture, it is a severe fracture where the bone breaks through the skin, increasing the risk of infection and requiring immediate medical attention.

simple/closed fracture

a fracture in which the broken bone does not penetrate the skin, meaning the skin remains intact over the site of the injury.

compression fracture

a fracture that occurs when the bone is crushed or collapses, commonly seen in the vertebrae due to osteoporosis or high-impact trauma.

axial skeleton

the central part of the skeleton, consisting of the skull, vertebral column (spinal cord), and thoracic cage (ribs and sternum), providing support and protection for the brain, spinal cord, and organs in the thorax

appendicular skeleton

the part of the skeleton that includes the bones of the upper and lower limbs, and the girdles (pectoral and pelvic) that attach them to the axial skeleton, enabling movement and manipulation of objects.

vertebrae

the individual bones that make up the vertebral column or spine, protecting the spinal cord and providing flexibility and support for the body. There are typically 33 vertebrae in humans.

osteoblast

a cell responsible for forming new bone tissue by synthesizing and secreting the organic matrix (osteoid) and minerals that make up bone; often called a bone-forming cell.

osteoclast

a large, multinucleated cell responsible for bone resorption, breaking down bone tissue by secreting acids and enzymes, playing a crucial role in bone remodeling and calcium homeostasis.

osteocyte

a mature bone cell, derived from an osteoblast, that maintains the bone matrix and plays a critical role in detecting mechanical stress on bone and initiating bone remodeling.

osteoporosis

a disease characterized by a decrease in bone mineral density and bone mass, leading to weakened bones and an increased risk of fractures, often associated with aging, hormonal changes, and nutritional deficiencies.

rickets

a bone disease occurring in children, caused by a severe deficiency of vitamin D, calcium, or phosphate, leading to softening and weakening of bones, bone pain, and skeletal deformities.

osteoarthritis

a common degenerative joint disease characterized by the breakdown of articular cartilage, leading to pain, stiffness, and loss of movement in the affected joints, primarily due to wear and tear over time.

long bone

bones that are longer than they are wide, characterized by a diaphysis (shaft) and two epiphyses (ends), primarily found in the limbs (e.g., femur, humerus), and function in support and movement.

sesamoid bone

small, independent bones or nodules of cartilage developed in a tendon where it passes over an angular structure, typically found in the hands and feet (e.g., patella or kneecap).

compact vs spongy bone

Compact bone is dense and forms the outer layer, providing strength and protection. Spongy bone is porous, found in the epiphyses and interior of bones, containing red marrow and providing strength without excessive weight.

synarthrosis

an immovable joint where bones are held tightly together, allowing little to no movement, such as the sutures in the skull.

amphiarthrosis

a slightly movable joint, allowing limited movement between bones, such as the pubic symphysis or the intervertebral discs.

diarthrosis

a freely movable joint, also known as a synovial joint, characterized by a joint capsule and synovial fluid, allowing a wide range of motion, such as the knee or shoulder joint.

other skeletal functions

• Mineral Storage: Stores calcium and phosphate

• Hematopoiesis: Production of blood cells in red bone marrow

• Fat Storage: Stores lipids in yellow bone marrow

• Movement: Provides attachment points for muscles, acting as levers

fibrous joints

joints where bones are held together by dense fibrous connective tissue, typically providing little to no movement (e.g., sutures of the skull, syndesmoses like between tibia and fibula).

cartilaginous joins

joints where bones are connected by cartilage, allowing for limited or no movement depending on the type of cartilage (e.g., symphyses like the pubic symphysis, synchondroses like the epiphyseal plate).

synovial joints

the most common and movable type of joint, characterized by a joint cavity filled with synovial fluid, an articular capsule, and articular cartilage, allowing for a wide range of motion (e.g., knee, hip, shoulder).

skeletal system functions

• Support: Provides a framework for the body

• Protection: Guards vital organs (e.g., brain, heart, lungs)

• Movement: Serves as attachment points for muscles, enabling locomotion

• Mineral Storage: Stores important minerals like calcium and phosphorus

• Blood Cell Formation (Hematopoiesis): Occurs in the red bone marrow

• Fat Storage: Occurs in the yellow bone marrow

periosteum

a dense, two-layered vascular connective tissue membrane that envelops the outer surface of bones, except at articular surfaces. It consists of an outer fibrous layer for protection and an inner osteogenic layer containing osteoblasts and osteoclasts, which contribute to bone growth in width, repair, and attachment for tendons and ligaments through Sharpey's fibers.

periosteum

a dense layer of vascular connective tissue that surrounds the bones, providing nourishment and serving as an attachment point for tendons and ligaments.