Chapter 7: Skeletal System

The adult human skeleton is composed of ____ bones.

206

The skeletal system ____ body structures an provides shape to the body.

Supports

The skeletal system ____ the soft and delicate internal organs.

protects

The skeletal system allows ____ and ____ of muscles.

movement and attachment

Ligaments

Fibrous bands that connect bones to bones and cartilage and serve as support for muscles.

Tendons

Fibrous cords that connect muscles to bone.

The skeletal system provides ___ storage. Serving as a depot for materials such as calcium and phosphorus.

mineral

The skeletal system is the site for ____, the formation of blood cells. In an adult, the ribs, sternum, and bones of the pelvis contain red marrow.

hematopoiesis

Osteocytes

Mature bone cells that maintain bone tissue.

Bone is made up of ___% organic material and ___% inorganic mineral salts and water.

35%, 65%

The organic portion of the bone is ____, a fibrous material with jellylike material in between the fibers. It gives the bone a certain degree of flexibility.

collagen

The inorganic portion of bone is made from mineral salts such as calcium phosphate, calcium carbonate, sodium oxide, and sodium chloride. These make the bones hard and ____.

Durable

The embryonic skeleton initially consists of collagenous protein secreted by osteoblasts. Later, ____ is deposited between the fibers. ____ is also found at the ends of certain bones in adults, providing a smooth surface for bones to move against each other.

Cartilage

During the 8th week of embryonic development, ___ occurs.

Ossification; Calcium-based material begins to replace the formed cartilage, creating bone. Infant bones are soft and pliable due to incomplete ossification.

Fontanel

Soft spots on a baby’s head where the bone has not yet formed.

Diaphysis

The central shaft of a long bone, a hollow cylinder composed of compact bone. It is what makes a long bone strong and hard yet light enough for movement.

Epiphysis

The end part of a long bone, initially separated from the diaphysis by a layer of cartilage. It contributes to joint articulation and houses red marrow.

Medullary Canal

The central cavity of a long bone that contains mainly yellow bone marrow and is involved in the production of blood cells.

Endosteum

The thin layer of connective tissue that lines the medullary canal and the spaces within spongy bone. It contains osteoblasts and osteoclasts and is involved in bone growth and repair.

Haversian Canals

The microscopic channels in bone that house blood vessels and nerves, facilitating nutrient and waste exchange within the bone matrix. They run vertically through the center of osteons.

Spongy/Cancellous Bone

A type of bone that is characterized by a porous, lattice-like structure, providing strength while reducing weight. It is found mainly at the ends of long bones and within the interior of others, and it houses bone marrow.

Trabeculae

The structural units of spongy bone, consisting of a network of thin plates that create a latticework appearance. They help to support bone strength while minimizing weight and are typically filled with bone marrow.

Periosteum

A dense external membrane that covers bones, serving as an attachment point for ligaments and tendons. Composed of tough, fibrous tissue. It contains blood vessels and nerves, contributing to bone nutrition and growth.

Articular Cartilage

A smooth, slippery tissue that covers the epiphyses in joints, allowing for easy movement and reducing friction between the articulating surfaces. Also acts as a shock absorber.

Bones grow and ossify from the center of the ___ toward the _____ extremities.

diaphysis, epiphyseal

Osteoblasts

Bone-forming cells that synthesize and secrete bone matrix, playing a crucial role in bone growth and repair. As bone girth increases, bone material dissolves from the central part of the diaphysis, forming the medullary canal.

Osteoclasts

Cells that break down bone tissue by secreting enzymes and are for bone remodeling and mineral release into the bloodstream. They digest bony material and split the minerals for use by the body (particularly calcium and phosphorus).

The length of a bone shaft continues to grow until the _____ is ossified.

Epiphyseal cartilage/plate

Bone remodeling

The process by which bone tissue is continuously renewed through the actions of osteoblasts and osteoclasts, allowing bones to adapt to stress and repair microdamage.

Resorption

The process by which osteoclasts break down bone tissue, releasing minerals back into the bloodstream.

Formation

The process by which osteoblasts create new bone tissue, contributing to bone growth and repair.

The average bone growth in females continues to about __ years of age; males grow for approximately 20-21 years.

18

The process of bone repair

Clot and granulation tissue formation, proliferation of cells at the site (soft bone deposit), remodeling of bone.

Long Bones

Bones that are longer than they are wide, primarily found in the limbs. They consist of a diaphysis and epiphyses, and are crucial for movement and support. Found in the upper and lower arms and legs.

Flat Bones

Bones that are thin and flat, providing protection to internal organs. Examples include the skull, ribs, and sternum.

Irregular Bones

Bones with complex shapes that do not fit into the other categories. They provide support and protection and include structures like the vertebrae and facial bones.

Short Bones

Bones that are as wide as they are long, mainly found in the wrists and ankles.

The ______ at a joint is determined by bone shape and joint structure.

Degree of movement

Axial Skeleton

The part of the skeleton that consists of the skull, vertebral column, and rib cage, providing central support and protection for the body's organs.

Hyoid Bone

A U-shaped bone located in the neck that supports the tongue and is not directly connected to any other bones.

There are ___ small bones in the ear.

six

Suture

An irregular band of connective tissue that holds cranial bones tightly together.