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Semester 1- MTM > The Structure & Function of Loose and Dense Connective Tissue > Flashcards

The Structure & Function of Loose and Dense Connective Tissue Flashcards

1
Q

What is connective tissue?

A

a diverse and abundant supporting tissue

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2
Q

what is the function of connective tissue?

A
  • structural support for body and organs
  • tensile strength
  • binding tissues together
  • immune defence
  • metabolism and energy storage (fat cells)
  • cushioning
  • elasticity
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3
Q

give examples of specialised connective tissue

A

bone, cartilage, blood, adipose, dentine and lymph

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4
Q

List the structural and functional characteristics of connective tissue that distinguish it from other basic tissue types (epithelial tissue)

A
  • In connective tissue the cells are separate and not packed like in epithelial tissue
  • Connective tissue has vast amounts of extracellular matrix whereas epithelial tissue has very little.
  • Connective tissue lies below the basement membrane (lamina propria) whereas epithelial tissue lies above the basement membrane.
  • Cells of connective tissue are bound by blood capillaries (to gain nutrients) whereas cells of epithelial tissue are not (gain nutrients via diffusion from the cells below them)
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5
Q

what are the 3 fundamental components of all connective tissue?

A

cells
extracellular matrix - fibres and ground substances

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6
Q

what are the 3 fibres in connective tissue?

A

Collagen
Elastin
Reticular

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7
Q

what are ground substances and name the 3 in connective tissue?

A
  • viscous clear substance that occupies the space between the fibres and the cells of connective tissue.
  • acts as a barrier for penetration by foreign bodies.
  • composed of:
    glycoproteins
    proteoglycans
    glycosaminoglycans (GAG)
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8
Q

what are fibroblasts?

A

‘blast’- means making
fibroblasts- make fibres
- have an elongated cigar shaped nucleus
- deposits all the extracellular matrix components (all fibres and ground substance)
- they secrete the precursors of GAG’s, collagen and elastin.
- its cytoplasm expands during synthesis of extracellular fibres and rER and golgi become more apparent.
- they maintain the continuous slow turnover of ECM components.

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9
Q

what is a fibrocyte?

A

the inactive state of a fibroblast, once it has deposited all ground substances and fibres

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10
Q

what is a plasma cell?

A

clock face nucleus, produces antibodies

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11
Q

what is an adipocyte?

A

Fat globule in centre (usually washed away during slide preparation)
Rim of cytoplasm is seen with the nucleus pushed to one end.
They store energy as fat

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12
Q

what is a macrophage?

A

phagocytic in function. The cells have ingested particles in their cytoplasm

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13
Q

what are eosinophils, neutrophils and lymphocytes?

A

eosinophils- 2 lobe nuclei, eosinophilic granules
neutrophils- multilobed nuclei, phagocytic functions
Lymphocyte- round nuclei with small cytoplasm white blood cells used in the immune response

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14
Q

what are mast cells?

A

contain many basophilic granules which store histamine and proteoglycans. These are released during allergic/inflammatory reactions.

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15
Q

what cells are wandering and which ones are fixed?

A

Fibroblast, fibrocyte, adipocyte and macrophage are fixed cells (or resident cells) in connective tissue
Plasma cells, Eosinophils, Neutrophils, lymphocyte, mast cells these are wandering cells which kills pathogens.

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16
Q

how do connective tissues carry out defence mechanism?

A
  1. Monocytes secrete cytokines to attract lots of other immune cells.
  2. Mast cells produce histamines making blood vessels leaky allowing white blood cells to enter the vessels easily.
  3. Macrophages are fixed cells already present in the connective tissue. They begin engulfing pathogens.
  4. Plasma cells, Eosinophils, Neutrophils, lymphocyte cells are extrinsic. They arrive via blood vessels and kill pathogens.
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17
Q

what are the cells of connective tissue?

A
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18
Q

what are collagen fibres?

A

Main and most abundant fibre type in the human body. It is secreted by fibroblasts into the ECM in the form of tropocollagen (monomer), which then polymerises to form collagen

19
Q

what are the properties of collagen fibres?

A

High tensile strength (however if you stretch them over 3% of original length they will break)
Thick bundled fibres
Do not branch
Flexible
Acidophilic (pink-stained)

20
Q

what are the 4 types of collagen fibres?

A

Type 1: dermis (skin) ligaments, tendons and bones
Type 2: cartilage
Type 3: make up reticular fibres (see below)
Type 4: forms mesh-like structures important in - basal laminar

21
Q

what are reticular fibres?

A

Crosslink to form a meshwork which is responsible for supporting the liver, spleen, bone marrow and lymph nodes.
Made up of Type 3 collagen fibres
Thin
Able to absorb metallic silver so are stained black

22
Q

what are elastic fibres?

A

Fibroblasts secrete tropoelastin (precursor form) which undergoes polymerisation in the extracellular tissues. Microfibrils of the structural glycoprotein fibrillin then become incorporated in an around to form elastin fibres

23
Q

what are the properties of elastic fibres?

A

Allows stretching and recoil to original shape e.g, cartilage of the ear
Thin fibres
Branched
Arranged in fibres or in discontinuous sheets in ECM
Loss of elastic fibres in the dermis of skin leads to wrinkling
Found: in the skin, lungs, arteries, veins

24
Q

what is the structure of the components of ground substances?

A
  • Each long unbranched GAG has many proteoglycans bound to it (via a link protein)
  • Proteoglycans are made up of a core protein with GAGs attached (This makes the sidechains charged)
  • Their charged sides chains are hydrophilic thus attracting water (trapping it within the matrix - makes the ground substance feel slippery) and ions, particularly sodium which makes up the extracellular fluid.
  • In loose connective tissue the main GAG backbone is hyaluronic acid.
  • In cartilage the GAG bound to the proteoglycan is chondroitin sulfate
  • In the dermis of the skin the GAG bound to the proteoglycan is dermatan sulfate.
25
Q

how does tissue fluid and ground substances interact?

A

Tissue fluid is associated with ground substance allowing passage of molecules and exchange of metabolites

26
Q

what are the 2 types of basic connective tissue?

A

loose
dense

27
Q

what is loose connective tissue?

A

plenty of ground substance with loose fibres (type 1 and 3 collagen and elastin) and scattered cells.

28
Q

where is loose connective tissue found?

A

Found within the lamina propria (under the basement membrane of epithelia)
Found surrounding blood vessels

29
Q

explain lamina propria as an example of loose connective tissue

A

immediately underlying certain epithelia
very thin CT layer
Ground substance + loosely arranged fibres Allows blood vessels to serve epithelial tissues above
Ad: Good for diffusion
Dis: Good breeding ground for microbes
Usually has immune cells

30
Q

what is the function of loose connective tissues?

A
  • Attaches epithelia to underlying tissue
  • Forms passages for blood vessels nerves and lymphatics.
  • Macrophages, mast cells, lymphocytes and plasma cells act as mobile ‘residents’ in loose connective tissues, and other white blood cells can be rapidly recruited from local blood vessels when required.
31
Q

what is dense connective tissue?

A

Less ground substance and fibroblasts and plenty of closely packed collagen fibres (dense)

32
Q

what are the 2 types of dense connective tissue?

A

dense regular
dense irregular

33
Q

what is dense regular connective tissue?

A

Type 1 Collagen fibres run in one direction. Dispersed fibroblast cells. Found in tendons (help anchorage) and ligaments (help in connecting). Resists tensile forces in one axis.

34
Q

what is dense irregular connective tissue?

A

Collagen fibres run transversely and longitudinally so you can see line and dots because of cut fibres. Found in the dermis of skin or capsule of joints. Resists tensile forces from all directions. This means the skin is resistant to tearing is all directions and in the capsule of joints it stops dislocation due to incoming force from all directions.

35
Q

what type of connective tissue is adipose tissue

A

loose connective tissue

36
Q

what are the 2 types of adipose tissue?

A

white
brown

37
Q

what is adipose white tissue?

A

Contains adipocytes which store lipids in a single vesicle (unilocular fat cell).
Their nuclei are peripherally located.
It forms the subcutaneous tissue
White adipose tissue is an important energy store and acts as thermal insulator under the skin.
It also acts as a shock absorber in areas, such as around the kidneys.
It is a pale staining as it contains mainly lipid
The cytoplasm is a thin rim around the periphery, containing mostly mitochondria.

38
Q

what is adipose brown tissue?

A

Contains adipocytes which store lipids in multiple vesicles (multilocular)
Nuclei are centrally located.
Responsible for generating heat 🡪 It is key in body temperature regulation.
Brown adipose tissue is found in new-born mammals and some hibernating animals.
Only a small amount is found in human adults.
Brown colour due to lots of mitochondria and capillaries

39
Q

what are genetic mutations connective tissue?

A

Type I collagen: osteogenesis imperfecta
- Brittle bones/ malformation

Type II collagen: Chondrodysplasia
- Cartilage defects, joint abnormalities

Type I, III or V collagen: Ehlers Danlos syndrome

Fibrillin: Marfan’s syndrome

40
Q

what is lipomas?

A

lump under the skin due to swelling of adipocyte cells.
It is simply a benign non-malignant harmless swelling

41
Q

what is an edema?

A

Excess accumulation of fluid within the tissue spaces
Pitting edema- leaves a pit when pressed down
Causes of edema:
CV disease (edema of extremities),
Renal disorders (puffiness of face)
Hyperthyroidism (generalised edema)

42
Q

what is Marfans syndrome?

A

Results from mutation in fibrillin gene.
Therefore, the tissue is less resistant to stretch as it has less functional elastic fibres
Risk of aortic aneurysms as the aorta walls are weak and stretch easily.
affects tissues rich in elastic fibres

43
Q

what is Ehler’s-Danlos syndrome?

A

A congenital abnormality resulting in abnormal production of collagen.
Symptoms: effects collagen containing connective tissue
Joints may be hypermobile
Hyper elasticity of the of skin
Bones are more prone to fracture
Fragile blood vessels etc.
Life span depends on the subtype of collagen fibres that are affected. Type 4 collagen fibres have the worse prognosis as they can lead to aortic rupture => death
extra elastic skin

Semester 1- MTM (15 decks)

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