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Histology > Connective Tissue > Flashcards

Flashcards in Connective Tissue Deck (94)
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1
Q

What are the four basic categories of cell in the body

A

Connective tissue

Nerve tissue

Muscle tissue

Epithelial tissue

2
Q

Supporting tissue is derived from which embryonic layer

A

Mesoderm

3
Q

What are connected tissue cells responsible for

A

The synthesis and maintenance of extracellular matrix

4
Q

What are the four types of connective tissue cells

A

Fibroblast

Adipocyte

Chondroblast and chondrocyte

Osteoblast and osteocyte

5
Q

What is the most common connective-tissue cell

A

Fibroblast

6
Q

What does a fibroblast look like and light microscopy

A

an elongated nucleus is usually the only visible structure

It can be difficult to distinguish other components due to the thickness of the cell and its fusiform shape tapering towards both ends

7
Q

What do you electron micrographs of mature fibroblasts look like

A

They show an elongated cell with a prominent nucleus and a scanty cytoplasm rich in rough ER

8
Q

Fibroblasts have a cytoplasm rich in rough ER. What does this reflect about the fibroblast’s role

A

It has a role in protein synthesis and secretion

9
Q

When activated what do fibroblasts give rise to in muscle

A

Myofibroblasts which have contractile function and play a role in tissue repair, defence and immunity

10
Q

What are the rules of white adipocytes

A

Energy storage

Protective cushioning

Thermal insulation

11
Q

How do you white adipocytes store fat

A

As a single lipid droplets occupies most of the cell, compressing and displacing the nucleus to one side

12
Q

What does a white adipocyte look like?

A

Has a sparse cytoplasm which is peripherally distributed as a thin layer around the lipid droplet

13
Q

How are white adipocytes distributed

A

They can be found on their own throughout loose and dense connective tissue or forming a solid tissue with very little intercellular material between them

14
Q

How do brown adipocytes store fat

What do these cells look like

A

As numerous lipid droplets

They have a large nucleus, numerous mitochondria whose cytochromes account for the brown colour and are smaller than white adipocytes

15
Q

Which organisms tend to have lots of brown adipocytes

A

Neonates and hibernating mammals

They have a key role in heat generation and body temperature regulation in such organisms

16
Q

What do chondroblasts and chondrocytes do

A

Secrete and maintain the extracellular matrix of cartilage

17
Q

What do osteoblasts and osteocytes do

A

Maintain the extracellular matrix of bone

18
Q

Describe the extracellular matrix

A

And organised meshwork of protein and polysaccharide molecules that fill the space between cells

It also participates in the regulation of cell differentiation, growth, shape, proliferation and migration

19
Q

How is the extracellular matrix synthesised and secreted

A

By fibroblasts

20
Q

What are the two components of extracellular matrix

A

Fibrous proteins e.g. collagen and elastin

Ground substance, a hydrated amorphous polysaccharide gel in which the fibrous proteins are embedded

21
Q

What is the most abundant protein in the body and what does it provide

A

Collagen

22
Q

What is the precursor of collagen

A

Tropocollagen / procollagen

23
Q

Where does assembly of tropocollagen into long collagen fibres occur

A

Extracellularly

24
Q

How many types of collagen are there and which is the most abundant

A

There are four types with type one being 90% of the total amount

25
Q

Where is type II collagen found

A

It consists of fine fibres embedded in cartilage matrix

26
Q

Where is Type III collagen found

A

Skin and round blood vessels

27
Q

Where is type IV collagen found

A

It forms a meshwork of fine fibres and is the main component of epithelial basement membranes

28
Q

How does collagen appear in LM

A

As an acidophilic mesh

Collagen molecules can only be seen as bundles, If they do not form a bundle they cannot be distinguished from the surrounding ground substance except by immunohistochemistry

29
Q

Describe the appearance of collagen one fibres under the EM

A

They have a striations at intervals of 67 mm along the length

This periodicity reflects the staggering of tropocollagen molecules in the fibres

30
Q

What do elastic fibres consist of

A

And amorphous glycoprotein called elastin and numerous proteinaceous microfibrils that become embedded in the elastin

31
Q

What synthesises elastin

A

It is synthesised in the fibroblasts as a precursor called tropoelastin

32
Q

What secretes the ground substance of the extracellular matrix

What does the aqueous phase of it allow

A

It is secreted primarily by fibroblasts and consists mostly of glycosaminoglycan and proteoglycan

The diffusion of salts, nutrients, hormones and metabolites between blood and tissue cells

33
Q

What are proteoglycans composed of

A

A core protein to which straight-chain polymers of repeating sugar heterodimers are covalently attached

These sugars differ giving different classes of proteoglycans

They are negatively charged and take on an extended form in tertiary structure

34
Q

The extracellular matrix contains glycoproteins. What are these?

A

Proteins to which she also branched oligosaccharide chains are covalently pound

the glycoproteins of ground substance are much smaller than proteoglycans

35
Q

Give examples of Glycoproteins in ground substance

A

Laminin (A component of basement membrane is that mediate attachment of epithelial cells)

Fibronectin (A component which promotes cell adhesion)

36
Q

True or false:

Ground substance is simply there to fill up the space

A

False

It contributes to the physical properties of the tissue

Ground substances orientate cells during development, control diffusion and are involved in healing and repair

37
Q

Describe loose connective tissue

A

The fibres (mostly collagen) are sparse ( 10–20% by volume) and the ground substance fairly fluid, providing ample opportunity for functional cellular growth and differentiation as well as space for considerable transient populations of white blood cells in places such as the gut epithelium

38
Q

Describe dense connective tissue

A

In some places, usually wear a polo or an expansion has to be resisted, the proportion of college and increases and a higher density of fibre is found

In places such as tendons and ligaments college and contribution can rise to 90% or more

39
Q

Describe elastic connective tissue

A

This shows a preponderance of elastic fibres and is found in the long Alviola sector, skin the wall of the year and your brother on the walls of the arteries

As tissues age the elastic content decreases

40
Q

Why does skin wrinkle with age

A

As tissues age the elastic content decreases

41
Q

What are chondroblasts

A

Connective tissue cells that produce the cartilage extracellular matrix consisting of connective-tissue fibres (mainly collagen and elastic fibres,) in the various proportions and abundant ground substance rich in proteoglycans

Secretion of the matrix traps the chondrocytes, separating them

42
Q

What is most cartilage surrounded By

A

A layer of irregular collagenous connective-tissue called perichondrium

This also contains some inactive fibrocytes

43
Q

What happens to the inactive fibrocytes in perichondrium

A

They can become chondroblasts in the inner surface

The Chondroblasts can grow, divide and produce new cartilage matrix

44
Q

Which are more mature:

chondrocytes or chondroblasts

A

Chondrocyte are more mature

45
Q

Where are chondrocytes found

What are they responsible for

A

They are located within small lacunae

Maintaining the integrity of the extracellular matrix

46
Q

How do you chondrocytes receive metabolites

A

Cartilage lacks blood vessels

So chondrocytes depend on metabolite diffusion from the capillaries at the edge through the water of the ground substance

47
Q

Describe hyaline cartilage

Where is it found

A

Contains abundant ground substance with scattered fibres to form a thick into cellular material

It is the commonest form of cartilage

In the trachea, nose, larynx , ribs and all articular surfaces

48
Q

How much of hyaline cartilage is ground substance and what kind of collagen does it to contain

A

70% ground substance

Type II cartilage

49
Q

Describe fibrocartilage

A

Contains abundant type II collagen fibres

This resilient cartilage is formed from alternating layers of hyaline cartilage matrix and layers of dense collagen fibres

50
Q

Where is fibrocartilage found

A

In intervertebral discs, where ligaments or tendons connect to bone and in the pubic symphysis

51
Q

Describe elastic cartilage

Where is it found

A

Has a structure similar to hyaline cartilage but contains abundant branching elastic fibres and Type II collagen

In the external air and external auditory canal as well as in part of the laryngeal cartilages and in the epiglottis

52
Q

How does bone differ from cartilage

A

Mineral salts are deposited in the intercellular material to give increased rigidity

53
Q

Why is blood considered to be a connective tissue

A

It originates in the mesoderm and has a matrix

54
Q

What do you all blood cells arise from

A

The same pluripotent uncommitted stem cell

55
Q

What is haematopoiesis?

A

The process of blood production which is usually carried out in the bone marrow

56
Q

What do pluripotent stem cells differentiate into

A

Progenitor cells which differentiate into various types of blood cells

57
Q

How many litres of red blood cells do we have

A

2 L

5x10^6 RBC per mm3

58
Q

How long is the lifespan of a human red blood cell

A

120 days

59
Q

What is the shape of a red blood cell

A

Biconcave

60
Q

What are reticulocytes

What do they contain

A

Immature RBCs that are releases from
The bone marrow to the circulation where they mature after 1-2 days

Some rER and small mitochondria

61
Q

What is the proportion of reticulocytes in human blood

A

1% of the total number of mature red blood cells

62
Q

How many blood cells are white blood cells

A

About one cell in 1000 blood cells is a leucocyte

63
Q

How are white blood cells classified

A

According to their appearance in the light microscope, the presence of granules in the cytoplasm and how the granules are covered with Leishmann’s stain

64
Q

How are white blood cells divided

A

Into granulocytes and agranulocytes

65
Q

Name the three granulocytes

A

Neutrophils

Eosinophils

Basophils

66
Q

Name the two types of agranulocytes

A

Lymphocyte

Monocyte

67
Q

What are thrombocytes

How big are they

A

Platelets

1-4μm in diameter

68
Q

Describe a platelet

A

Non-nucleated, by convex fragments formed in the bone marrow from the cytoplasm of megakaryocytes

They contain the most cytoplasmic organelles of any cell

69
Q

What consists of ~20% of the platelet volume

A

Electron dense granules containing serotonin and many proteins

70
Q

How many platelets are there

A

150-400x10^3 per μm of normal circulating blood

71
Q

What is the role of platelets

A

Haemostasis (control of bleeding)

Plugging sites of vascular damage

Facilitating vascular repair

72
Q

What are granulocytes generally

A

White blood cells with cytoplasmic granules that contain substances that participate in inflammatory and allergic responses

73
Q

Describe a neutrophil

A

Contains neutrophilic granules that do not stain well

It is best to identify them by the fact that the nucleus is divided into several lobes – the polymorphic nucleus

Neutrophils are the most numerous am on the white blood cells

74
Q

What percentage of white blood cells are neutrophils

A

60%

75
Q

What are eosinophils?

A

Eosinophilic Granules of relatively uniform size that stain red or orange with acidic dyes

76
Q

How do the sizes of eosinophils and neutrophils compare

A

Eosinophils > neutrophils

77
Q

Describe basophils

A

Contain course but you do feel like granules that staying with basic dies and pick up azure and stain blue

The granules vary in size and shape and a larger than those of eosinophils

These are the rarest I’m on the white blood cells making up only 1% of total leucocytes

78
Q

Describe a lymphocyte

A

Cells with a round nucleus and a clear scanty cytoplasm

79
Q

Describe a monocyte

A

A large cell with an indented bean shaped, curved nucleus and abundant cytoplasm

80
Q

Describe the function of neutrophils

A

They are the first line defence against infectious pathogens

They ingest and destroy antibody /antigen complexes and bacteria

The granules contain hydrolyses as well as proteolytic, lipolytic and carbohydrate digestive enzymes

The chemicals they release course fever and inflammatory responses

81
Q

What is the main constituent of pus

A

The dead remnants of neutrophils

82
Q

What is the half life of neutrophils

A

6 hours In Circulation

83
Q

How do many neutrophils into the tissues

A

between the endothelial cells of capillaries by dispedesis

84
Q

What do eosinophils do

What is the half life like

How do they enter tissue

A

Release inflammatory substances and kill parasites

The number increases in allergic reactions eg asthma

V short

Through capillary walls

85
Q

What do basophils do

A

Enter tissues and release inflammatory substances and histamine when activated

They play a part in the stomach anaphylaxis and hypersensitivity reactions which results in the release of vasoactive agents from their granules

86
Q

Name two things found in basophil granules.

A

Histamine

Heparin (an anticoagulant)

87
Q

How are lymphocytes divided

A

Functionally into B- and T- lymphocytes
Both of which help acquire immunity

NK cells (natural killer cells) Are larger and much less abundant than B- or T- lymphocytes and play a role in innate immunity

88
Q

Discuss B lymphocytes

A

Produced in the bone marrow and involved in the production of circulating antibodies

89
Q

Discuss T lymphocytes

A

Involved in cell mediated immunity

Produced in bone marrow but complete their maturation in the thymus

90
Q

What is the half life of a monocyte

What happens after this

A

~72 hours

They enter the tissues and become tissue macrophages

As macrophages they show avid phagocytosis and are important in and ingesting and destroying bacteria and foreign particulate material

91
Q

Tissue macrophages comprise…

A

Kupffer cells of the liver

Macrophages of the pulmonary alveolus (dust cells)

Microglia of the brain

92
Q

What are mast cells

A

Granulated, wondering cells that originate in the bone marrow but are released into the circulation as mast cell progenitors that mature when they are in the tissue

93
Q

What do the granules of mast cells contain

A

Histamine

Heparin

Proteases

94
Q

Where are mast cells found

What are other functions of mast cells

A

In areas of connective-tissue where they play A role in inflammatory responses e.g. post defence to invading parasites and allergic reactions

Recruitment of immune cells, smooth muscle contraction and increased vascular permeability