BioSci 107 - Connective Tissues

What are the three important things about connective tissue?

1. Binds, supports and strenghtens other body tissues

2. Major transport system of the body (blood is a CT)

3. Major site of stored energy reseves (fat is a CT)

Where is connective tissue found?

It is found in bones, cartilage, where blood is located (not on body surfaces)

Is connective tissue highly vascular?

Yes, with the exception of cartilage which is avascular and tendons with very little blood supply

What does CT have in common with epithelia?

It is supplied by nerves

What is connective tissue composed of?

Composed of extracellular matrix (ECM) and cells

What is ECM compposed of?

1. Ground substance (GS)

2. Protein fibres

What does ECM do?

1. Protein fibres of ECM are secreted by the cells in the ECM/CT

2. Structure of the ECM largely dictates the CT qualities e.g cartilage: ECM is firm and rubbery. bone: ECM is hard and inflexible

What is ground substance is composed of?

1. Water

2. Proteins (gelatin in jelly)

3. Polysaccharides (sugars)

What else is sugar known as?

Glycosaminoglycans (GAGS or mucopolysaccharides)

What does GAGS do?

Join with core proteins to form proteoglycans

What is GAGS?

Long unbranched chains of sugar, repeating disaccharide unit

What is proteoglycans made up of?

Core protein and glycosaminoglycan

What does sulphated GAG do?

Bind core proteins to form proteoglycans (PGs), sulphate helps water binding)

What are examples of sulphated GAG?

1. Dermatan sulphate

2. Heparin sulphate

3. Keratan sulphate

4. Chondroitin sulphate

What are examples of non-sulphated GAG?

Hyaluronic acid, it does not bind directly to protein backbone but is joined to various PGs

What makes glycosaminoglycan hyaluronic acid unusual?

It is not sulphated or covalently bound to a core protein (still binds lots of water). It is highly polar and attract water.

What does hyaluronic acid do?

Viscous slippery substance binds cells together, lubricates joints and maintains shape of eyeball

What is hyaluronidase?

1. Produced by white blood cells, sperm and some bacteria

2. Makes GS more liquid so they can move more easily in it or makes access to egg easier for sperm

What is chondroitin sulphate?

Support and provide features of cartilage, bone, skin and blood vessels

What is keratan sulphate?

Found in bone, cartilage and cornea of eye

What is dermatan sulphate?

Found in skin, tendons, blood vessles and heart valves

What happens if there is abnormal ECM?

Exopthalmos where eyes swell up, more common in younger women, swollen thyroid gland and autoimmune over-activation of thyroid

What increases orbital contents?

Deposition of glycosaminoglycans and the influx of water

What are the three different types of connective tissue fibres in ECM?

1. Collagen fibres (thick)

2. Reticular fibres

3. Elastic fibres

Whats the function of collagen fibres?

1. Very strong but flexible to resist pulling forces

2. Features vary in different tissue e.g more water around collagen in cartilage than in bone

3. It is the most abundant protein

4. Commonly found in bone, cartilages, tendons and ligaments

5. Parallel bundles

What makes up reticular fibres?

1. Composed of collagen with coating of glycoprotein

2. Collagen in fine bundles with coating of glycoprotein (more protein than sugar)

3. Made by fibroblasts

Whats the function of reticular fibres?

1. Provide strength and support

2. Form part of the BM

3. Thinner, branching - spread through tissue

4. Form networks in vessels and through tissues especially adipose tissue, nerve fibres, smooth muscle tissues

What is elastic fibres composed of?

1. Thinner than collagen fibres

2. Fibrous network

3. Consists of the protein elastin surrounded by the glycoprotein fibrillin to give more strength and stability

4. Can be stretched 150% without breaking

5. Found in skin, blod vessels and lung

What is marfan syndrome?

Hereditary defect in elastic fibres usually resulting from a dominant mutation in the gene on chromosome 15, codes for fibrillin. Body produces growth factor TBFb increasing growth because does not bind normally to fibrillin to keep it inactive

What are the results of marfan syndrome?

Tall, long limbes and often with a chest deformality, occurs in about 1 in 20,000 births

What are the two common CT cell types?

1. Fibroblasts

2. Adipocytes (fat cells)

Where is fibroblasts located?

Widely distrubted in connective tissues; migratory

What is the function of fibroblasts?

Secrete components of the matrix (fibres and GS)

Where is adipocytes located?

Under skin and around organs

What is adipocytes function?

Store fat (triglycerides)

What are other important cells found in solid CT?

1. Macrophages (histiocytes)

2. Plasma cells

3. Mast cells

4. Leucocytes

What are macrophages?

Cells that eat and remove dead tissue, bacteria and debris.

What are the types of macrophages?

1. Dust cells in lungs

2. kupffer cells in liver

3. langerhans cells in skin

4. Wandering macrophages, move around CT especially in infection, inflammation or injury

What are plasma cells?

Cells that come from B-lymphocytes

What do plasma cells do?

Produce antibodies to help fight infections

Where are plasma cells found?

1. Gut

2. Salivary glands

3. Lymph nodes

4. Spleen

5. RB marrow

What are mast cells?

Cells located near blood vessels

What do mast cells do?

1. Release histamine

2. Histamine dilates blood vessels

Why are mast cells important?

Helps with inflammation and immune responses (like allergies)

What are leucocytes (WB cells)?

Immune cells found in blood e.g neutrophils and eosinophils

What does leucocytes do?

Migrate out of the blood into tissues to fight infection

What are two classification of CT?

1. Embryonic CT

2. Mature CT

What are the subtypes of embryonic CT?

1. Mesnchyme (embryonic)

2. Mucous

Whats the structure, location and function of mesnchyme?

Consists of CT cells found in semi-fluid GS containing reticular fibres and gives rise to all other connective tissue

Whats the structure, location and function of mucous?

Has widely scattered fibroblasts embedded in jelly-like GS and supports umbilical cord of fetus

What are the 3 categories for mature CT?

1. Connective tissue proper

2. Fluid connective tissues

3. Supporting connecitve tissues

What are the 3 types of loose CT?

1. Areolar CT (most common form)

2. Adipose CT

3. Reticular CT

What is Areolar CT?

Loose so has many cells and fewer fibres, subtype is aerolar

What is the structure/location/function of areolar CT?

3 types of fibres are present (collagen, reticular and elastic), widely distributed around almost every structure, gives strength, elasticity and support

What is adipose CT?

Loose so has many cells and fewer fibres, subtype is adipose

What is the structure/location/function of adipose CT?

Form: adipocytes dominante; central triglyceride droplet.

Found with areolar CT (including fibroblasts) and used for insulation, energy source and temperature control

What is white and brown adipose used for?

White is used for enegry storage and brown is used for heat production

What is reticular CT?

Loose so many cells and has less fibres, subtype is reticular

What is the structure/location/function of reticular CT?

Form: Reticular cells dominant (special type of fibroblasts)

Found and makes filter for RBC in spleen and microbes in lymph nodes

Serves as a stroma of organs (framework or scaffold that cells can move on), binds smooth muscle

What are the 3 types of dense CT?

1. Dense regular CT

2. Dense irregular CT

3. Elastic CT

What is dense regular CT?

Dense so has more fibres and fewer cells, subtype is dense

What is the structure/location/function of dense regular CT?

Form: regularly arranged collagen e.g tendons (pulling along fibre axis) and is shiny white colour

Found in tendons (bone to muscle), ligaments (bone to bone) and aponeuroses (muscle to muscle; muscle to bone)

Used for slow healing, tension strength along axis of fibres

What is dense irregular CT?

Dense so more fibres and fewer cells, subtype is irregular

What is the structure/location/function of dense irregular CT?

Form: Collagen fibres irregularly arranged around few cells

Found in sheets called fasciar and us used for tensile (pulling) strength in many directions

What is elastic CT?

Dense so more fibres and less cells, subtype is elastic

What is the structure/location/function of elastic CT?

Form: Mainly elastic fires with some fibroblasts between

Found in lung tissue, elastic arteries, bronchial tubes, true vocal cords, suspensor lig of penis, some intervertebral ligaments

Used for stretching with strong recoil - think lungs

What are the 3 types of supporting CT?

1. Hyaline cartilage

2. Fibro cartilage

3. Elastic

What is hyaline cartilage?

Cartilage dense network of collagen and elastic fibres, subtype is hyaline

What is the structure/location/function of hyaline cartilage?

Form: Glistening ; abundant

Relatively weak, resilient gel in which fibres are present but not obvious enough.g anterior ends of ribs; respiratory cartilage i.e nose, tranchea, bronchi

Used for flexibility and movement

What is fibrocartilage

Type of cartilage, subtype fibrocartilage

What is the structure/location/function of fibrocartilage

Form: dense network of collagen fibres with scattered chondrocytes

Found in pubic symphysis; intervertebral discs; menisci of knee, any tendons that join cartilage

Works to support and joining of structures together, strongets type of cartilage

What is elastic cartilage?

Type of cartilage, subtype is elastic

What is the structure/location/function of elastic cartilage?

Form: chondrocytes in thread like network of elastic fibres within extracellular matrix

Found in epiglottis; auricle of external ear, auditory eustachian tubes

Works for strength and elasticity, maintain shapes of structures

What is bone tissue? (Supporting CT)

Bones are organs composed of several connective tissue types, including bone tissue

What are the 2 types of bone tissue?

1. Compact bone

2. Spongy bone

What is compact bone?

Outer layer of bone and forms the shaft of long bones. Composed of many rod-shaped units known as either osteons or haversian systems

What is spongy bone?

Porous inner bone tissue that lies underneath compact bone. Bone marrow found around this bone tissue, lacks osteons

What is the structure/location/function of compact bone?

Contains osteons, stores calcium and phosphorous, used for protection and support

What is the structure/location/function of spongy bone?

Lacks osteons, stores triglycerides (yellow marrow) and produces blood cells (red marrow)

What are the 4 cell types found in bone?

1. Osteogenic cells

2. Osteoblasts

3. Osetocytes

4. Osteoclasts

What are osteogenic cells?

Mesenchymal stem cells that develop, starts to lay down collagen; become trapped and become osteoblasts

What are osetoblasts?

Bone forming cells, lay down more collagen, mineralisation process starts

What are osteocytes?

Mature bone cells derived from osteoblasts trapped wiithin the extracellular matrix, maintain bone tissue and involved in exchange of nutrirents and wastes, has gap junctions

What are osteoclasts?

Large multinucleated cells, formed from the fusion of blood monocytes and break down bone

What is the structure of osteons? (haversian systems)

1. Lamellae

2. Lacunae

3. Canaliculi

4. Central (haversian) canal

What is lamellae?

Concentric rings of mineral salts for hardness and collagen for tensile strength

What is lacunae?

Small spaces between lamellae that contain mature bone cells (osteocytes)

What is canaliculi?

“Minute canals” (containing EC fluid and minute osteocytic processes) that radiate from lacunae and provide routes for oxygen, nutrients and waste

What is central (haversian) canal?

Blood, lymph and nerves

What does osteoclasts do in fracture?

Reabsorb dead bone

What does chondroblasts do in fracture?

Lay down hyaline cartilage callus

What does osteoblasts do in fracture?

Lay down new bone

What does osteoclasts do in fracture?

Remodel new bone

What are the types of fluid CT?

Liquid CT blood

What is liquid CT blood?

Liquid subtype blood

What is the structure/location/function of liquid CT blood?

Consists of blood plasma (a liquid extracellular matrix) and formed elements (red cells, white cells and platelets)

What do erythrocytes (RBC) do?

Transport oxygen and carbon dioxide in the blood

What are leukocytes?

White blood cells that combat disease

Which leukocytes are phagocytic and engluf bacteria?

1. Neutrophils

2. Monocytes (macrophages)