a&p ch 6 bones

Bone functions

Shape Support Protection Movement Electrolyte balance Blood production Acid-base balance

Acid-base balance:

Bone absorbs and releases alkaline salts to help maintain a stable pH.

Blood production:

Bones encase bone marrow, a major site of blood cell formation.

Protection:

Bones protect delicate internal organs.

Electrolyte balance:

Bones store and release minerals such as calcium and phosphorus.

Medullary cavity:

Central, hollow portion

What is the basic structural unit of bone? Osteon Lacunae Canaliculi Osteocyte

Osteon

Periosteum:

A dense, fibrous membrane covering the diaphysis; some of the fibers of the periosteum penetrate the bone, whereas other fibers weave together with the fibers of tendons to ensure a strong connection between muscle and bone; the periosteum contains bone-forming cells and blood vessels, making it crucial for bone survival

Osteocytes:

Are mature osteoblasts embedded in hardened bone matrix

types of bone tissue

Compact bone - Forms shafts of long bones and surfaces of other bones Spongy (cancellous) bone - Found in ends of long bones and middle of other bones Compact bone is dense and solid. Spongy bone is always surrounded by compact bone.

Articular cartilage:

Covers the epiphysis; eases the movement of the bone within a joint

Which of the following is not one of the functions of bone? A. Electrolyte balance B. Blood production C. Acid-base balance D. Regulation of blood glucose

D. Regulation of blood glucose

Osteoclasts:

Dissolve unwanted bone

Endochondral ossification

Early in the life of a fetus, long bones are composed of cartilage; these cartilaginous bones serve as "models" for bone development. Osteoblasts start to replace the chondrocytes (cartilage cells), coating the diaphysis in a thin layer of bone. They then produce a ring of bone that encircles the diaphysis. Soon, the cartilage begins to calcify. Blood vessels penetrate the cartilage, and a primary ossification center develops in the middle of the diaphysis. The bone marrow cavity fills with blood and stem cells. Ossification continues—proceeding from the diaphysis toward each epiphysis—and the bone grows in length. Eventually, secondary ossification centers appear in the epiphyses.

Endosteum:

Epithelial membrane lining the medullary cavity

Red bone marrow:

Fills the medullary cavity in children; in adults, most marrow has turned to yellow marrow

Osteoblasts:

Help form bone

Diaphysis:

Hollow cylinder made of compact bone; gives the bone strength

fracture repair

Initial hematoma transforms into granulation tissue. Granulation tissue transforms into a soft callus. A hard callus forms around the fracture. Remodeling replaces the callus tissue with bone.

Movement:

Movement of the arms and legs, as well as the ability to breathe, results from the interaction between muscles and bones.

Bone tissue

Osteoblasts: Help form bone Osteoclasts: Dissolve unwanted bone Osteocytes: Are mature osteoblasts embedded in hardened bone matrix

Osteocytes have a dual role:

Some dissolve bone, whereas others deposit bone. This contributes to the maintenance of bone density whereas helping regulate blood levels of calcium and phosphorus.

bone development Intramembranous ossification Endochondral ossification

The bones of skull and face start out as connective tissue. Then groups of stem cells in the tissue differentiate into osteoblasts. Clusters of osteoblasts (called centers for ossification) deposit matrix material and collagen. Eventually, calcium salts are deposited and the bones are calcified. This is called intramembranous ossification. Most bones evolve from cartilage: After about 3 months' gestation, the fetus has a skeleton composed mostly of cartilage. At that time, the cartilage begins to turn into bone. This process, which begins in long bones, is called endochondral ossification.

Epiphyseal plate:

The layer of cartilage separating the epiphysis from the diaphysis at the ends of a long bone in growing children (When growth stops, it is replaced with an epiphyseal line.)

fracture

a break in a bone

Spongy (cancellous) bone

always surrounded by compact bone. Found in ends of long bones and middle of other bones

Short bones

are about as broad as they are long; they tend to be shaped like cubes. Examples include the carpal bones of the wrist and the tarsal bones of the ankle.

Trabeculae

are arranged in a way that offers maximum strength. If the stress a bone is exposed to changes, the trabeculae will realign to compensate. The cavities between the trabeculae are filled with bone marrow.

Layers of matrix

are arranged in concentric rings (called lamellae) around a central canal (called a haversian or osteonic canal).

Long bones

are longer than they are wide; they work like levers to move limbs. Examples include the femur of the thigh and the humerus of the arm.

Irregular bones

are often clustered in groups; they come in various sizes and shapes. Examples include the vertebrae and facial bones.

Sesamoid bones

are small bones imbedded in tendons. The kneecap is an example of a sesamoid bone.

Flat bones

are thin, flat, often curved bones; they protect organs (such as the bones of the skull, the ribs, and the sternum). Other flat bones (such as the scapulae) provide a large surface area for the attachment of muscles.

Spongy, or cancellous,

bone consists of a latticework of bone called trabeculae. Trabeculae are arranged in a way that offers maximum strength. If the stress a bone is exposed to changes, the trabeculae will realign to compensate. The cavities between the trabeculae are filled with bone marrow.

compound fracture

bone has pierced the skin, damage to surrounding tissue, nerves, and blood vessels may be extensive, broken through the skin and at risk for infection

closed reduction

broken bones can be manipulated into their original position without surgery

Transverse passageways connect the haversian canals.

called Volkmann's canals, These canals transport blood and nutrients from the bone's exterior to the osteocytes locked inside.

Microscopic passageways connect the lamellae to each other.

called canaliculi

Tiny gaps between rings of the lamellae

called lacunae, contain osteocytes.

A fetus' first skeleton is composed primarily of: epithelial tissue. osseous tissue. cartilage. fibrous connective tissue.

cartilage.

Bone matrix consists of

collagen fibers and crystalline salts (primarily calcium and phosphate); the matrix of bone is hard and calcified. Bone has a strength rivaling that of steel and reinforced concrete.

Bone widening

continues through life span.

Compact bone

dense and solid. Forms shafts of long bones and surfaces of other bones

Bone lengthening occurs at the

epiphyseal plate, which is a layer of hyaline cartilage at the each end of bone. On the epiphyseal side of the cartilage plate, chondrocytes multiply. As these cells move toward the diaphysis, minerals are deposited and the cartilage becomes calcified. As long as chondrocytes are produced in the epiphyseal plate, the bone continues to elongate. Between the ages of 16 and 25, the cartilage of the epiphyseal plate is replaced with spongy bone. Bone lengthening stops. What remains is a line of spongy bone called the epiphyseal line. Bone widening and thickening continue throughout the life span: Osteoblasts in the periosteum lay down new layers of bone around the outside of the bone, whereas osteoclasts on the inside of the bone dissolve bone tissue. This widens the marrow cavity. Bone remodeling (resorption and ossification) continues throughout life.

Shape: Bones

give the body its structure.

greenstick fracture

incomplete fracture, similar to when a green stick breaks, occurs in young kids because their bones have more collagen than adults, causing the bone to splinter rather than break completly

Bone marrow

is a type of soft tissue that fills the medullary cavity of long bones and the spaces of spongy bone. Red bone marrow is charged with producing red blood cells. Nearly all of a child's bones contain red bone marrow. In an adult, red bone marrow can only be found in the ribs, sternum, vertebrae, skull, pelvis, and the upper parts of the humerus (arm) and femur (thigh). All other bones contain yellow marrow. Yellow bone marrow replaces red marrow over time. The cells of yellow marrow are saturated with fat and no longer produce blood cells. In cases of severe, chronic blood loss or anemia, yellow marrow can change back into red marrow.

Red bone marrow

is charged with producing red blood cells. Nearly all of a child's bones contain red bone marrow. In an adult, red bone marrow can only be found in the ribs, sternum, vertebrae, skull, pelvis, and the upper parts of the humerus (arm) and femur (thigh). All other bones contain yellow marrow.

spiral fracture

line spirals around the bone, the result of a twisting force, the jagged bone ends often make it hard to reposition, seen in child abuse

Collagen fibers in the matrix

make bone highly resistant to stretching forces (tensile strength); calcium salts allow bones to resist strong squeezing forces. (compressional strength); bone cannot endure much twisting (torsional strength).

Bone lengthening

occurs at epiphyseal plate for fixed period.

Bone is called

osseous tissue.

Bone cells are

osteoblasts, osteoclasts, and osteocytes.

This basic structural bone unit is called an

osteon.

Yellow bone marrow

replaces red marrow over time. The cells of yellow marrow are saturated with fat and no longer produce blood cells. In cases of severe, chronic blood loss or anemia, yellow marrow can change back into red marrow.

bone fractures

simple compound greenstick comminuted spiral

open reduction

surgery is needed to reposition the bones, after which screws, pins, or plates may be used to stabilize the bone

comminuted fracture

the bone is broken into pieces, occurs in car accident

simple fraction

the bone remains aligned and the surrounding tissue is intact

Blood vessels and nerves run the length of the bone, through

the center of the canal.

Support

the legs, pelvis, and spinal column support the body and hold it upright.