Lecture 3: The tissues of the human body - connective Flashcards
Connective tissue
It binds, supports, and strengthens other body tissues.
A major transport system of the body (blood is a connective tissue).
A major site of stored energy reserves (fat or adipose tissue is a connective tissue).
It
It binds, supports, and strengthens other body tissues.
A major transport
A major transport system of the body (blood is a connective tissue).
A major site
A major site of stored energy reserves (fat or adipose tissue is a connective tissue).
Features of Connective tissues
Unlike Epithelia
CT is NOT found on body surfaces
(Think of where bones, cartilage, and blood are located…)
CT can be highly vascular
(Exceptions: cartilage, which is avascular, and tendons, which have very little blood supply)
Like Epithelia
CT is supplied by nerves
(Exception: cartilage)
Unlike epithelia
CT is NOT found on body surfaces
(Think of where bones, cartilage, and blood are located…)
CT can be highly vascular
(Exceptions: cartilage, which is avascular, and tendons, which have very little blood supply)
Like epithelia
CT is supplied by nerves (exception: cartilage)
CT is composed of:
Extracellular Matrix (ECM)
Cells
Formula:
CT = ECM + Cells
ECM (I)
Ground Substance (GS)
Protein Fibres (3 major types in different proportions)
Formulas:
CT = ECM + Cells
ECM = GS + Fibres
ECM (II)
Protein fibres of the ECM are secreted by the cells in CT.
Structure of the ECM determines connective tissue qualities:
Cartilage → Firm and rubbery
Bone → Hard and inflexible
GS (Ground substance) (I)
Water
Proteins (e.g., gelatin in jelly)
Polysaccharides (sugars)
Formula:
GS = H₂O + Proteins + Polysaccharides
GS (II)
The sugars in GS are Glycosaminoglycans (GAGs) (also called mucopolysaccharides).
GAGs combine with core proteins to form proteoglycans.
Glycosaminoglycans (GAGs) (I)
Also called mucopolysaccharides.
They are long, unbranched polysaccharides.
GAGS (II)
Repeating Disaccharide Unit
* Amino sugar (e.g., N-acetylglucosamine)
* Uronic sugar (e.g., glucuronic acid)
Proteoglycans
Core Protein + Glycosaminoglycan (GAG)
Sulphated GAG Examples
- Dermatan sulphate
- Heparin sulphate
- Keratan sulphate
- Chondroitin sulphate
These bind to core proteins to form proteoglycans (PGs).
Non-Sulphated GAG Example
- Hyaluronic acid
Hyaluronic acid does not bind directly to the protein backbone but is joined to various PGs.
Hyaluronic acid (I)
The glycosaminoglycan hyaluronic acid is unusual in that it is not sulphated or covalently bound to a core protein.
Hyaluronic acid (II)
Highly polar and attract water so collectively, the glycosaminoglycans trap water to make the ground substance more jelly-like.
Application of GAGS (I)
Hyaluronic Acid: viscous slippery substance binds cells together, lubricates joints and maintains shape of eyeball
Hyaluronidase (I)
produced by some white blood cells, sperm and some bacteria.
Hyaluronidase (II)
This makes ground substance more liquid so they can move more easily in it or makes access to the egg easier for sperm.
Application of GAGS as part of ground substance
Chondroitin Sulphate: support and provide the adhesive features of cartilage, bone, skin, blood vessels.
Keratan Sulphate: found in bone, cartilage, cornea of the eye
Dermatan Sulphate: found in skin, tendons, blood vessels, heart valves
Sometimes can get abnormal ECM ground substance
Chondriotin sulphate
Chondroitin Sulphate: support and provide the adhesive features of cartilage, bone, skin, blood vessels.
keratan sulphate
Keratan Sulphate: found in bone, cartilage, cornea of the eye
Dermatan sulphate
Dermatan Sulphate: found in skin, tendons, blood vessels, heart valves
Sometimes
Sometimes can get abnormal ECM ground substance
Abnormal Periorbital ECM and thyroid disease (Exophthalmos)
Most common in younger women
Goitre (swollen thyroid gland)
Autoimmune over-activation of thyroid (goitre)
Autoimmune action on fibroblasts in ECM of eye (exophthalmos)
The deposition of glycosaminoglycans and the influx of water increase the orbital contents.
Most
Most common in younger women
Goitre
Goitre (swollen thyroid gland)
Autoimmune over
Autoimmune over-activation of thyroid (goitre)
Autoimmune action
Autoimmune action on fibroblasts in ECM of eye (exophthalmos)
The deposition
The deposition of glycosaminoglycans and the influx of water increase the orbital contents.
There are 3 different types of connective tissue fibres in the ECM
ECM = GS + Fibres
Collagen fibres
Reticular fibres
Elasic fibres
Collagen fibres (I)
Very strong but flexible to resist pulling forces
Features vary in different tissues, e.g., more water around collagen in cartilage than in bone.
Collagen fibres (II)
Collagen makes up 25% of your body and is the most abundant protein!
Common in: bone, cartilages, tendons, and ligaments
Parallel bundles
Reticular fibres (I)
Composed of collagen with coating of glycoprotein
Collagen in fine bundles with coating of glycoprotein (more protein than sugar)
Made by fibroblasts
Reticular fibres (II)
Provide strength and support
Form part of the basement membrane
Thinner, branching – spreads through tissue
Reticular fibres (III)
Form networks in vessels and through tissues, especially adipose tissue, nerve fibres, smooth muscle tissues
Elastic fibres (I)
Thinner than collagen fibres
Fibrous network
Elastic fibres (II)
Can be stretched 150% without breaking
Found in skin, blood vessels, and lung.
Elastic fibres (III)
Consist of the protein elastin surrounded by the glycoprotein fibrillin to give more strength and stability.
Marfan syndrome (I)
A hereditary defect in elastic fibres usually resulting from a dominant mutation in a gene on chromosome 15, which codes for fibrillin.
Marfan syndrome (II)
Fibrillin is a large glycoprotein (350 kDa) that contributes to a structural scaffold for elastin.
Marfan syndrome (III)
Body produces growth factor Transforming Growth Factor beta (TGFβ) – increases growth because it does not bind normally to fibrillin to keep it inactive (theory).
Marfan syndrome (IV)
Individuals with Marfan Syndrome are: usually tall, long-limbed, and often have a chest deformity (e.g., protruding or collapsed sternum). Normal life span but need medical vigilance to control BP, etc.
Marfan syndrome (V)
They may have weakened heart valves and arterial walls, which can be life-threatening.
Occurs in about 1 in 20,000 live births.
Two common Connective tissue cell types
Other cells cound in Solid CT
Classification of CT
Embryonic or mature
Embryonic connective tissues
Mature Connective Tissues
Apidose Connective Tissue
Dense regular connective tissue
Supporting CT: Cartilage
Supporting CT: Bone or osseous tissue
Bones are organs composed of several connective tissue types, including bone tissue (which is either compact or spongy (BM)).
Compact bone
- Outer layer of bone and forms the shaft of long bones.
- It is also known as cortical bone.
- Composed of many rod-shaped units known as either Osteons or Haversian systems (see soon).
Spongy bone
Porous inner bone tissue that lies underneath compact bone.
Also known as Cancellous bone.
Lacks osteons.
Bone
4 cell types found in bone
Osteogenic cells:
Osteoblasts:
Osteocytes:
Osteoclasts:
Osteogenic cells:
Mesenchymal stem cells that develop, start to lay down collagen, become trapped, and transform into osteoblasts.
Osteoblasts:
Bone-forming cells that lay down more collagen, initiating the mineralization process.
Osteocytes:
Mature bone cells derived from osteoblasts, trapped within the extracellular matrix.
Maintain bone tissue.
Osteocytes:
Involved in exchange of nutrients and wastes.
Have gap junctions.
Osteoclasts:
Large, multinucleated cells.
Formed from the fusion of blood monocytes.
Break down bone.
Osteons has 4 parts
- Lamellae:
- Lacunae:
- Canaliculi:
- Central (Haversian) cana
Osteons are aligned along lines of stress (e.g. long axis of bone
shaft).
Lamelle
oncentric rings of mineral salts for hardness (e.g.
calcium phosphate and calcium hydroxide, which together
form hydroxyapatite) and collagen (for tensile strength).
Lacunae
mall spaces between lamellae
that contain mature bone cells (osteocytes)
Canaliculi
“minute canals” (containing EC fluid and
minute osteocytic processes) that radiate from lacunae
and provide routes for oxygen, nutrients and waste.
Central (Haversian) canal:
blood, lymph and nerves
CT: blood
Consists of blood plasma (a liquid extracellular matrix)
and formed elements (red cells, white cells and platelets)
Erythrocytes
transport oxygen and carbon dioxide
Leukocytes
Leukocytes combat disease:
i. Neutrophils and monocytes (macrophages) are
phagocytic, engulfing bacteria.
ii. Basophils (mobile) and Mast cells (immature
circulate; mature are fixed in tissues), release
substances (e.g. histamine) that intensify the
inflammatory reaction.
iii. Eosinophils are effective against certain parasitic
worms and in acute allergic response .
iv. Lymphocytes are involved in the immune
response.
Platelets (from megakaryocytes in red marrow): clotting.
i. Neutrophils and monocytes (macrophages)
are phagocytic, engulfing bacteria.
ii. Basophils (mobile) and Mast cells
(immature circulate; mature are fixed in tissues), release substances (e.g. histamine) that intensify the inflammatory reaction.
iii. Eosinophils
are effective against certain parasitic
worms and in acute allergic response .
iv. Lymphocytes
are involved in the immune
are involved in the immune
response.
Platelets (from megakaryocytes in red marrow): clotting.
