Mod 23 - Bone Tissue Part 1

5 functions of the skeletal system

Support

Protection

movement

Storage

Blood cell production

How does the skeletal system provide support

bone, cartilage, ligaments

How does the skeletal system provide protection

Surrounds organs

How does the skeletal system provide movement

muscles pulling on bones to move via tendons

How does the skeletal system provide storage

Ca and P stored and released when needed

fat stored in marrow cavities (yellow marrow)

How does the skeletal system provide blood cell production

Bone marrow produces blood cells

Characteristics of cartilage

Firm, smooth, resilient, non-vascular CT

What is cartilage made of

Cartilage cells

Matrix (70-85% water, protein, ground substance)

What does the amount of water do to cartilage

gives it its resiliency

What does protein do to cartilage

give its it strength

What are the 3 types of cartilage

hyaline, elastic, fibrocartilage

Characteristics of hyaline cartilage

Most common

Joints

associated with bone

used in embryological development, nose, trachea, articulate cartilage

Characteristics of fibrocartilage

Strongest

Collagen fibres

In areas that need more support

In between body of vertebrae, knee

Characteristics of elastic cartilage

flexible

auricle of ear

lots of elastic fibres

What does bone develop from

cartilage

What is the main cell type in cartilage

chondrocytes

What are immature chondrocytes called

Chondroblasts

What is the perichondrium

Double layer of CT that covers cartilage

Nerve and blood supply

Why is articulate cartilage hard to repair

no perichondrium so no blood supply

What is appositional growth

Growth on outside of cartilage beneath perichondrium

Chondroblast secrete matrix and trap themselves to create chondrocytes

What is interstitial growth

Happens in region with mature cartilage

Mature chondrocytes divide into many cells

When are interstitial and appositional growth common

Interstitial - child and during puberty

Appositional - After puberty

What is the difference between bone and cartilage

Bones constantly breakdown and replace bone matrix

What is the bone matrix made of

65% inorganic

- Hydroxyapatite: calcium phosphate crystals

35% organic

- Collagen/proteoglycans, water

What are the organic parts of the bone matrix responsible for

Flexible strength

What are the inorganic parts of the bone responsible for

Compressive (weight-bearing) strength

What builds the framework of the bone cells

Collagen and proteoglycans vesicles

What fills up the vesicles to make calcify the bone

Ca2+ and PO43- hydroxyapatite

What do osteochondral progenitor cells do

stem cells that become osteoblasts or chondroblasts

What are osteocytes

when the osteoblast surround themselves by bone matrix

Maintain ability to produce components necessary to maintain bone matrix

What is the canaliculus

a small channel in the matrix of bone to transport nutrients and oxygen

What are osteoclasts

Large cells that resorb or break down bone using acids and enzymes

Process of how osteoclasts break down bone

1. Osteoclast bind to bone via podosomes and creates a sealed compartment

2. ruffled border is made

3. releases acid and enzymes into compartment to break down bone

4. bone fragments taken up into osteoclast and released on the opposite side to get dissolved in blood

Why are do we break down bones

To use the minerals inside bone if needed when body levels are low