Lecture 3: Connective Tissue

Connective Tissue Function

Tissue that binds, supports, strengthens other body tissues. A transport system. Site of stored energy reserves (Fat). Is supplied by nerves, not found on body surfaces, can be vascular.

Composition of CT

CT = ECM + Cells

Composition & Function of ECM

ECM = Ground substance (GS) + Protein Fibres (3 major types)

The structure of the ECM largely dictates the CT qualities

Composition of GS

GS = Water + Proteins + Polysaccharides (Glycosaminoglycans/GAGS)

GAGS

GAGS bind to core proteins to create proteoglycans.

AKA long unbranched polysaccharides

Sulphated GAG examples

Dermatan sulphate, Heparin sulphate, Keratan sulphate, Chondroitin sulphate

Dermatan sulphate Location

Found in skin, tendons, BV

Keratan Sulphate Location

Found in bone, cartilage

Chondroitin Sulphate Location & Function

supports and provides structural integrity cartilage, skin, bone, BV

Non- Sulphated GAG

Hyaluronic acid

Instead it is joined to multiple proteoglycans, good at retaining water (physical buffer)

Hyaluronidase

Enzyme produced by WBC & some bacteria which liquifies GS for easier movement

Exophthalmos

Condition caused by abnormal deposition of GAGS affecting the eye, especially in cases of autoimmune thyroid disease

Collagen fibres

Strong, flexible to pulling forces. Found in bone, cartilage, tendons, ligaments

Reticular Fibres

Bundles of collagen with glycoprotein coating, providing support and forming networks in BV, adipose tissue.

Formed by fibroblasts

Elastic Fibres

Composed of elastin and fribilin, for stretching, stability. Found in BV & skin

Fibroblasts L&F

Secretes ECM components (GS and fibres)

Adipocytes (Fat cells) L&F

Stores fat, found under skin and around organs

Macrophages L&F

Phagocytic cells for immune response. Sites of inflammation, injury

Plasma Cells L&F

Produce antibodies, derived from B-lymphocytes. Found in spleen, gut, lung

Mast Cells L&F

Produce histamines for inflammation found alongside BV, and they are fixed in tissue

Leukocytes L&F

WBC involved in immune defence e.g neutrophils, eosinphils, Basophils, lymphocytes

Basophils L&F

They’re mobile and releases substances that intensifies the inflammatory reaction

Eosinophils L&F

Effective in acute allergic response

Lymphocytes L&F

Involved in the immune response

Platelets

Useful for clotting

2 Classifications of CT

Embryonic & Mature

Mesenchyme L&F

Embryonic tissue and the first to develop in embryonic gives rise to all other CT

Mucous CT L&F

Embryonic tissue found in the umbilical cord giving support and flexibility

Loose CT - Loose areolar tissue L&F

Has all 3 fibres, strength, elasticity, support

Loose CT - Loose adipose tissue L&F

Adipocytes (fat) dominant, insulation, energy source, temp control

Loose CT - Dense regular tissue L&F

Reguarly arranged collagen, slow healing, attachment. Tendons, ligaments, aponeuroses

Dense CT - Dense irregular tissue L&F

Composed of collagen fibres for strength and resistance. lymph nodes, digestive tract

Dense CT - Dense Elastin Tissue L&F

Elastin & Collagen for stretch in aorta and arteries

Fluid CT - Blood

Made up of blood plasma (liquid ECM) & formed elements (white cells, red cells, platelets)

Supporting CT - Hyaline Cartilage

Dense network of collagen & elastin for movement. Nose, trachea, bronchi

Supporting CT - Elastic Cartilage

Collagen & Elastin & chondrocytes, flexibility and strength

Supporting CT - Fibrocartilage

Tough, inflexible. Found in joints and tendons

Supporting CT - Spongy Bone L&F

lacks osteons, stores fat and produces blood cells, lies underneath compact bone

Supporting CT - Compact Bone L&F

Contains osteons, useful for protection and support, stores calcium and phosphorus, outer layer of bone

1. Osteogenic Cells L&F

Start to lay down collagen , become trapped and become osteoblasts

2. Osteoblasts

Bone forming cells, lay downs more collagen, mineralization process starts

3. Osteocytes

Mature bone cells trapped in the ECM they maintain bone tissue

4. Osteoclasts

Break down bone and large

Structure of Osteons (Haversian Systems)

1. Lamellae

2. Lacunae

3. Canaliculi

4. Central (Haversian) canal

1. Lamellae L&F

Rings of mineral salts for hardness which form collagen and other materials

2. Lacunae L&F

Small spaces between lamellae that contain mature bone cells

3. Canaliculi L&F

Contains EC fluid and provides routes for oxygen, nutrients and waste

4. Central Haversian Canal L&F

Contains blood, lymph and nerves