Histology of the Connective Tissue

Question 1

what is connective tissue made from?

which cells are connective tissues derived from?

what are role of connective tissue cells?

Answer 1

1. made from cells and ECM
2. derived from mesoderm.
3. role: storage of metabolites, immune / inflam reponse and tissue repair

Question 2

whar are the different classifications of connective tissue?

Answer 2

1. embryonic connective tissue

- mesenchyme

• mucous connective tissue

2. adult connective tissue

• loose connective tissue
• dense connective tissue

3. specialised connective tissue

• cartilage
• bone
• adipose tissue
• hemopoeitic tissue
• lymphatic tissue

Question 3

what is mesenchyme?

what does embroynic mesenchyme give rise to?

Answer 3

- loose tissue

• found in embryo and umblical cord
• embryonic mesenchyme gives rise to muscle, vasuclar and uro-genetial systems and serous membranes

Question 4

explain what mesenchyme embryonic connective tissue is like

Answer 4

mesenchyme

• embryo
• small spindle shaped
• ECM is filled with viscous ground substance
• collagen fibres are very fine and relatively sparse

Question 5

explain what mucous embryonic connective tissue is like

Answer 5

mucous connective tissue (wharton’s jelly)

• umbilical cord -> protects umbilical cord vessels (fibroblasts, macrophages)
• cells are seperated and look like fribroblasts
• thin collagen fibres

Question 6

how do we classify adult connective tissue?

what is adult connective tissue derived from

Answer 6

classifications:

• amount / number of collagen fibres
• organisation of collagen fibres
• type of collagen fibres

derived from: fibroblasts

Question 7

what are two types of adult connective tissue?

Answer 7

loose connective tissue

dense connective tissue

Question 8

for loose connective tissue, explain

a) structure
b) location
c) the site of what?
d) morphology?

Answer 8

loose connective tissue

structure:

a) thin and few fibres, but more cells.

b) abundant gel-like ground substance (facilitates diffusion of small molecules)

location: beneath epithelial tissue (dermis) (generally mucose or submucosa around BV, nerves, muscles)

site of: inflammatory and immune response

morphology: collagen fibres are thicker than elastic fibres, fibroblasts and mast cells presnet

Question 9

what are the two types of dense connective tissue?

Answer 9

regular and irregular dense connective tissue

Question 10

what is dense regular connective tissue characterised by?

what is dense regular connective tissue the main functional component of ?

Answer 10

dense regular connective tissue

• densely packed arrays of fibres and cells, all go same direction
• good resistance to pulling forces
• can stretch
• little ECM (c.f. loose connective tissue and irregular connective tissue)
• parralel bundles of collagen fibres (wavy appearance) and rows of fibroblasts - fibroblasts known as tendinocytes are surrounded by specialised ECM that seperates them from collagen fibres.

main functional component of:

- tendons, ligaments and cornea

Question 12

what are differences between tendons and ligaments?

Answer 12

tendons

• MUSCLE TO BONE

ligaments

• fibres are less regularly arranged
• BONE TO BONE
• can provide some elasticity

Question 13

describe the structure of dense irregular connective tissue

what does the structure allow with movement?

Answer 13

• mostly collagen fibres. few cells (of fibroblasts)
• fibres are arranged in bundles in various directions (unlike dense regular connective tissue)
• in hollow organs -> esp. submucosa (layer beneath epi. lining of organ)

- allow stretching and distension

Question 14

what is dense connective tissue type called that has more elastic tissue?

Answer 14

elastic tissue lol

- found between vertabrae

Question 15

what are the three types of connective tissue fibres?

Answer 15

1. collagen fibres

2. reticular fibres / tissue

3. elastic tissue

Question 16

• describe collagen fibre macrostructure
• what do collagen fibres look like under a) light and b) electron microscope?

Answer 16

macrostructure: triple helix of 3 polypeptides

shape: a) light microscope - wavy appearance. b) electron micrscope - bundles of fine, threadlike units

(need to know what stain?)

Question 17

• name strongest to weakest type of collagen

Answer 17

1. stength:
   - type 1, type 2, type 3, type 4:

- strongest —————> weakest

2. where are each type found?

Question 18

where is type 1 collagen found?

Answer 18

• type 1: bones, skin, tendons, fascia, cornea, teeth, mature scars

Question 19

where is type 2 collagen found?

Answer 19

cartilage, vitreous humor

Question 20

where is where is type 3 collagen found?

Answer 20

embroynic tissue, uterus, blood vessels

Question 21

where is type 4 collagen found?

Answer 21

basal membane

Question 22

where are reticular fibres found?

what do they support?

what associated with?

what is layout of cells like?

what made from?

what ar produced by?

Answer 22

• supporting stroma for highly cellular organs (like liver).
• found at boundary of connective tissue and epithelium.

- wound healing and scar tissue.

• branching pattern -> loose to allow passage of cells and fluid
• made of type III collagen. dont bundle
• produced by fibroblasts

Question 23

elastic fibres:

• where found?
• what look like?
• structure like compared to collagen?
• (stained with?)

Answer 23

• found in ligaments of vertebral column

- spring-like appearance

• thinner than collagen fibres

- (stained with orcein)

Question 24

what is ECM made of?

Answer 24

1. proteoglycans
2. collagens
3. noncollagenous glycoproteins (fibronectin and laminin)

Question 25

what are two categories of connective tissue cells? which are cells that make up each

Answer 25

**resident cells** - fibroblasts and myofibroblasts - macrophages - adipocytes - mast cells - adult stem cells **wandering cells - travel through hematopoietic system** - lymphocytes - plasma cells - neutrophils - eosniophils - basophils - monocyres

Question 26

- why are fibroblasts the main cells of the connective tissue? - what is shape like?

Answer 26

**fibroblasts:** - _principle cell bc_**: synthesis collagen and reticular fibres** - _shape:_ s**pindle shaped with elliptical nucleus (**squeezed at one end) (only nucleus visible under H&E)

Question 27

what are myofibroblasts like morphologically? - how are different to fibroblasts?

Answer 27

**myofibroblasts:** (- appear similar to fibriblasts) - express **alpha smooth muscle actin.** **-** differ from smooth muscle cells bc lack **external basal lamina**

Question 28

what do macrophages look like?

Answer 28

- kidney shaped nucleus - (micrscopically only visible when display phagocytic activity)

Question 29

what do mast cells look like? where ARE they present ? where NOT?

Answer 29

- large cells with **spherical** **nucleus** - large **basophilic granules in cytoplasm** (anitgen presenting cells) - found IN: CT of **skin and mucous** - NOT found in: **brain and spinal cord ( remember this!!)**

Question 31

what do mast cells react in response to?

Answer 31

inflammation

Question 32

what do adipocytes look like? do?

Answer 32

**- store** **fat** and produce variety of **hormones** **-** round cells**. nucleus** located on **periphery**

Question 33

what type of connective tissue is this?

Answer 33

**dense regular** CT

Question 34

what type of dense CT this?

Answer 34

elastic tissue

Question 35

what type of dense CT is this?

Answer 35

dense irregular CT

Question 36

what is the name of the thick layer of dense irregular connective tissue in the skin?

Answer 36

reticular layer