A&P CH.6

compact bone

solid; denser and less porous; lamallae oriented around blood vessels that pass through rugh bone;

Steps of intramembraneous ossification

- Osteblast formation - spongy bone formation - compact bone formation

enchondral ossification steps

- cartilage model formation - bone collar formation: compact bone on surface - primary ossification center formation - secondary ossification center formation; created in the epiphyses by migrating osteoblasts - Adult bone

Processes of calcium homeostasis

1. stimulation of skeletal muscles contraction 2. stimulation& regulation of cardiac muscle contraction 3. exocytosis of cellular molecules

Bone Matrix

35% organic: collagen and proteoglycans 65% inorganic: calcium and phosphate hydroxyapatite

Osteocytes

90-95% of bone cells; inactive; connected through cell extensions; cell bodies are housed in lacunae, while cell extensions are housed in canaliculi

Parathyroid hormone

A hormone of the parathyroid gland that regulates the metabolism of calcium and phosphorus in the body.

Cartilage growth #1

Appositional growth: chondroblast in pericardium add new cartilage to outside of existing cartilage.

bone repair step 4

Bone remodeling eventually replaces the callus tissue with bone

Function #5 of the skeletal system

Blood cell production- cavities filled with red bone marrow that raises count of blood cells and platelets.

Function #3 of the skeletal system

Body Movement- contraction of muscles; muscles attached by tendons; joints that are two or more bones coming together that allow movement between themselves.

bone repair step 3

Callus ossification. Callus replaced by woven, cancellous bone

Cartilage growth #2

Interstitial growth: chondrocytes in the center of tissue divide and add matrix between existing itng cells

Calcitonin

Lowers blood calcium levels

calcium homeostasis

Maintenance of a stable level of calcium in the blood

Function #4 of the skeletal system

Mineral Storage- if minerals in body decrease, the bones release them (like calcium); adipose tissue also stored; if needed lipids are released into blood as sources of energy.

Function #2 of the skeletal system

Organ protection- bone is hard so it is able to protect the organs that it surrounds.

Functions of the skeletal system

Support, organ protection, movement, mineral storage, blood cell production,

Function #1 of the skeletal system

Supports- body structure with ligaments (bands of fibrous connective tissue)

Fontanels

The larger, membrane-covered spaces between the developing skull bones that have not yet been ossified.

Bone development- Intramembraneous Ossification

about 8 weeks of emryonic development- 2 years of age; centers have oldest bones, edges have younger bone. * end products: compact surfaces of bone with spongy centers *

Osteoblasts

bone building cells; produce collagen and proteoglycans; secrete matrix vesicles; ossification- creating new bone; occurs by appositional growth

effects of aging in bone #1

bone matrix decreases; less collagen; bone is brittle

Components of the Skeletal System

bones, cartilage, tendons, ligaments

osteoclasts

break down bone (reabsorption); important for metabolic processes;

bone repair step 2

callus formation; mass of bone tissue that forms at a fracture site; external callus connects the broken ends of bone; internal callus forms between the ends of broken bone and marrow cavity macrophages clean osteoclast breaks down dead tissue fibroblast produce collagen fibers and denser fibrous network.

What does the matrix contain?

collagen and proteoglycans that provide strength and make it resilient by trapping water.

Articular cartilage

covers the ends of bones that come together to form joints; no pericardium, blood vessels or nerves.

Woven bone

first type of bone that forms during ossification; immature; collagen fibers are randomly oriented;

Lamellar bone

forms after woven bone has been broken down; mature; organized into thin sheets called lamellae which are about 3-7micrometers thick; collagen fibers are adjacent to lamellae;

Factors affecting bone growth

genetics: nutrition: vitamin D for absorbtion of calcium, Vitamin C for synthesizing collagen, hormones: Growth hormone increases general tissue growth, thyroid hormone if a decrease then individuals are much smaller, reproductive hormones like estrogen and testosterone

bone repair step 1

hematoma formation; blood vessels damaged; clot;

Cartilage types

hyaline, fibrocartilage, elastic

effects of aging in bone #2

increased bone fracture

Chondrocytes

is surrounded by matrix; are rounded cells that reside in lacuna

Spongy bone

less matrix and porous; consists of interconnecting rods or plates called trabeculae;

Hyaline Cartilage

most identified with bone; how all bones starts off as;

Bone remodeling

ongoing replacement of old bone tissue by new bone tissue

osteocytes are derived from

osteoblasts

Basic multicellular unit

osteoblasts, and osteoblasts that travel through or across the surface of bone; 6 month life span

Perichondrium

protective connective tissue sheath; contains fibroblasts; blood vessels and nerves penetrate the outer-layer;

Chondroblasts

secrete matrix and are located within the cells of the perichondrium membrane

osteochondral progenitor cells

stem cells that can become osteoblasts or chondroblasts; located in the inner layer of perichondrium and in connective tissue that covers bone;

Osteon

structural unit of compact bone

Trabeculae

thin and have several lamellae with osteocytes within lacunae; filled with bone marrow; along mechanical stress lines;