Lecture 5: Skeletomuscular System

Skeletal System Function & What is it composed of?

Provides support

Protects tissues

Stores minerals

Forms blood cells

Axial skeleton, appendicular skeleton, teeth

How are skeletal and muscular systems conencted?

Cartilage (supportive connective tissue)

Ligaments (dense regular connective tissue)

Tendons (dense regular connective tissue)

Ligaments

Connects bone to bone

Matrix: Collagen and some elastin

Tendons

Anchors bone to muscle

Matrix: Mostly collagen and little to no elastin

Bone tissue (matrix composition and strength)

Matrix: Collagen, calcium salts, hydroxyapatite

Matrix strength: Strong, relatively rigid

Cartilage (matrix composition and strength)

Matrix: Chondroitin sulfates (+ proteins forming proteoglycans)

Matrix strength: Relatively flexible

Cartilage characteristics

Avascular (no blood vessels)

Contains chondrocytes residing in lacunae (little holes/pockets)

Perichondrium

Dense fibrous connective tissue layer

On the surface of cartilage

3 subtypes of cartilage

Hyaline, elastic, fibrocartilage

Hyaline, elastic, and fibro- cartilage components

Proteoglycans

Proteoglycans + elastin fibres

Proteoglycans + extra collagen

Bone tissue characteristics

Highly vascularized (supplied with blood)

Innervated (nerves are inside of tissue)

Periosteum

Dense membrane that covers the outer surfaces of bones

Endosteum

Thin membrane that lines the inner surfaces of bones

Subtypes of bone tissue organization

Compact and spongy bone

Compact bone structure

Dense to resist compression

Cells in lacunae, organized in cocentric rings separated by layers of matrix

Around the perimeter

Osteon and where are the blood vessels?

Bullseye rings of multiple layers within the central part of a piece of compact bone

Local blood vessels @ centre of osteon

Spongy Bone

Light and distributes force

Spaces round the trabeculae are filled with bone marrow (to decrease weight)

Better at equally resisting force in all directions compared to compact

Trabeculae

Small rod-shaped tissue structures providing mechanical support and internal framing

Bone tissue cell types

Osteogenic cells, osteoblasts, osteocytes, osteoclasts

Osteogenic cells

Produce other bone cells (stem cell)

In periosteum and endosteum

Osteoblasts

Produce bone matrix

In periosteum and endosteum

Osteocytes

Maintains bone matrix

Connected to one another to share contents of cytoplasm

In lacunae

Osteoclasts

Dissolves bone matrix

In endosteum

Calcium homeostasis

Osteoblasts continuously deposit new bone matrix

Osteoclasts erode existing matrix, releasing calcium and phosphate ions into circulation

Hormonally regulated