TOB S5 - Connective Tissues and Skin Flashcards Preview

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Flashcards in TOB S5 - Connective Tissues and Skin Deck (108):
1

What is the embryonic origin of connective tissues?

Mesoderm

2

What are the three basic components of connective tissue?

Cells
Extracellular fibres
Amorphous ground substance

3

What are the basic functions of connective tissues?

Supporting organs
Filling spaces between organs
Forming tendons and ligaments

4

What are the Resident cell types in connective tissues?

Fibroblasts/cytes
Mesenchymal cells
Macrophages aka. Tissue histocytes

5

What are the Visitant cell types in connective tissues?

Mast cells
Plasma cells
Adipocytes
Leukocytes

6

What is the function of fibroblasts/cytes in connective tissues?

Synthesise and maintain extracellular matrix (Including collagen, elastic fibres, reticular fibres and ground substance)

Fibrocytes are more mature and less active fibroblasts.

7

What is the function of Mesenchymal cells in connective tissues?

Undifferentiated cells that differentiate into other cells and maintain extracellualar materials

8

What is the function of macrophages in connective tissues?

Ingest foreign material (bacteria, dead cells, cell debris)

9

What type of cells are macrophages derived from?

Monocytes

10

Give the specific names of monocytes found in:

The Liver
The CNS
Bone

Liver - Kupfer cells
CNS - Microglia
Bone - Osteoclasts

11

What is the function of mast cells in connective tissues?
Give 2 examples of molecules found in these cells.

Congregate near blood vessels and release pharmacologically active molecules

Eg Heparin, Histamine found in granules in the cell

12

What is the function of adipocytes in connective tissues?

Found in small clusters or aggregates, they store lipids and act as a insulator and shock absorber (cushioning organs and joints).

13

What is the function and derivation of leukocytes in connective tissues?

Derived from blood cells, responsible for production of immunocompetent cells

14

How does composition of connective tissue determine function?

The constituents of the extracellular matrix define whether the tissue is a loose packing tissue or of primary mechanical importance

15

What are the three fibres found in connective tissue's extracellular matrix?

Collagen
Reticular
Elastic

16

In what form does collagen occur in connective tissues?
Where does collagen synthesis occur?

Occurs in bundles of non-elastic fibres of variable thickness

RER of cells

17

What is the most common type of collagen?

Type 1

18

Describe the composition and form of Reticular fibres

Made up of type three collagen.

Forms thin branching fibres that form delicate networks around certain structures

19

Around what structures might a network of reticular fibres be found?

Blood vessels, adipocytes, smooth muscle cells, nerve fibres, certain epithelial cells

20

Around what organs do reticular fibres form a structural framework/supporting mesh?

Liver
Spleen
Bone Marrow
Lymphoid organs

21

Describe the structure and function of Elastic fibres

Highly elastic fibres containing amorphous protein and elastin surrounded by fibrillin

Can stretch up to 150% restin length due to high lysine content

22

Describe the structure and function of the amorphous ground substance in connective tissue

Gel like matrix in which fibres and cells are imbedded. Tissue fluid diffuses through it.

Composed of Glycosaminoglycans (GAGs), Proteoglycans and glycoproteins.

23

Where is loose connective tissue found in organs?

Forms the septa (walls) and trabeculae (rods) that make up the framework inside organs

24

How might loose connective tissue become distended?

During Oedema distended by Extracellular fluid (ECF)

25

Describe the composition of mucous connective tissue (Wharton's Jelly)
Where it might be found?

Large stellate fibroblasts (that will often fuse with similar adjacent cells)

Few macrophages and lymphocytes present

Ground substance has high concentration of Hyaluronic acid and a network of fine collagen fibres

Only found in Umbilical cord and Subdermal connective tissue of the embryo

26

Where might Areolar connective tissue be found?

Deep under the skin
Submucosa
Below mesothelium of peritoneum
Associated with adventitia of blood vessels
Surrounding parenchyma of glands

27

In terms of loose connective tisse what are the distinguishing features of areolar connective tissue

Contains fibroblasts and macrophages as well as some mast cells

Collagen fibres abundant but elastin fibres also present.

28

In terms of Loose connective tissue what is unique about the structure of Adipose tissue?

Loose connective tissue with adipocytes occuring singularly or in groups between collagen fibres

Adipocytes make up the majority of cells

29

What are the 4 common types of Loose connective tissue?

Areolar
Adipose tissue
Reticular tissue
Mucous connective tissue

30

How does the structure of Dense connective tissue vary from loose connective tissue?

Closely packed fibres
Fewer cells
Less ground substance

31

What is the defining feature of dense regular connective tissue and how does this relate to function?

Where is dense regular CT found?

Fibres oriented in parallel to provide maximum tensile strength

Tendons, Aponeuroses (flattened tendons) and Ligaments

32

How does fibre arrangement in ligaments differ from tendons?

Collagen fibres in ligaments less regularly arranged

33

In what types of Dense regular connective tissue can fibroblasts be found?

All of them

34

What is an elastic ligament?

A ligament where most fibres are elastin

35

What is a fascicle in a tendon?

A bundle of collagen and fibroblasts

36

Where does Loose connective tissue occur in tendons?

Endotendineum (layers of LCT interspersed through collagen)

Peritendineum (outer layer of LCT around tendon)

37

What surrounds tendons?

A fibrous sheath

38

Describe the structure of Dense irregular connective tissue and relate this to function

Collagen fibres criss cross in many directions to counteract multidirectional forces to which the tissue is subjected.

Mostly collagen with some elastic and reticular fibres

39

Where might Dense irregular connective tissue be found?

Deep fascia of muscles
Dermis of skin
Periosteum
Perichondruim
Dura matter
Capsules, large septa and trabeculae of many organs

40

What causes Systemic Sclerosis and what does it cause?

Excessive accumulation of collagen (fibrosis) in all organs

Causes hardening and functional impairment

41

What is a keloid scar and why do they form?

Scars on the skin caused by abnormal amounts of collagen

42

What is the result of vitamin C deficiency?

Defective collagen synthesis leading to degeneration of connective tissue.

Peridontal ligament is highly affected due to high collagen turnover

Loosening of teeth in their sockets with subsequent loss.

43

What causes Marfan's syndrome and what is a major effect of this?

Genetic defect in gene coding for fibrillin leading to undeveloped elastic fibres.

Large elastic arteries (eg. Aorta) can rupture due to weakened connective tissue.

44

What is the result of Ethlers-Danos disease?

Deficiency of type 3 collagen causing ruptures in tissue with high reticulin content.

45

What macroscopic features of skin are subject to variation?

Colour
Hair
Thickness
Laxity/Wrinkling
Oiliness

46

What reasons are behind variations in skin colour?

Ethnicity
UV exposure
Site (lips/areolar)

47

What reasons are behind variation in skin hair?

Site (Armpit vs Palm)
Sex (Facial and more profuse body hair in men)
Age (baldness in men, greying in both sexes)
Ethnicity (colour, character)

48

What are the reason/s behind variation in skin thickness?

Site (scalp vs ball of foot)

49

What factors affect skin laxity/wrinkling?

UV exposure
Site
Age

50

What factors might affect skin oiliness?

Puberty
Site

51

How does variation in skin colour influence presentation of vitiligo?

Much less of a problem in fair skinned as it is barely visible.

52

How does variation in skin colour influence susceptibility to skin damage or skin cancer?

Fair skinned more susceptible to:

UV induced acute sunburn
Freckling
Ageing
Skin cancer

53

What is the type of cell found in the epidermis?

Stratified squamous keratinised epithelium made up mainly of keratinocytes

54

What are the four layers of the epidermis?

Give in descending order.

Horny layer(stratum corneum)
Granular layer(stratum granulosum)
Prickle cell layer(stratum spinosum)
Basal layer(stratum basale)

55

Describe the processes of keratinocyte mitosis and differentiation

Keratinocytes from the stratum basale move upwards after undergoing mitotic division to form the stratum spinosum, where terminal differentiation begins

They then lose their ability to divide

56

What do keratinocytes produce?

Synthesise Keratins

57

What are the functions of keratins in the skin?

Contribute to strength of epidermis

Main constituent to hairs and nails

58

Describe the molecular structure of keratins.

Heterodimeric fibrous proteins

59

What changes to keratinocytes occur as they move into the granular layer?

Lose their plasma membrane

Begin differentiating into corneocytes (main cells of the stratum corneum)

60

Apart from cells, what is another component of the stratum granulosum?

Keratohyalin granules

61

What is the composition of keratohyalin granules?

Keratins

Other fibrous proteins (eg Filaggrin, involucrin)

Enzymes which degrade the phospholipid bilayer of cells
E.g. Phospholipases

Crosslink proteins (eg Filaggrin, involucrin)

62

What are the functions of filaggrin and involucrin?

Filaggrin: Aggregates keratins

Involucrin: Forms a major part of corneocyte envelope

63

What type do cells make up the stratum corneum?

What is the function of the stratum corneum?

Made up of layers of flattened corneocytes

Major function is as a barrier (resists abrasion etc)

64

What is the transit time from stratum basale to stratum corneum for a cell?

30-40 days

65

What are melanocytes, what is their embryonic origin and where are they found?

Dendritic cells of neural crest origin

Stratum basale

66

What is the function of melanocytes?

How does ethnicity effect their function?

Produce melanin

Produces more melanin in darker skin

67

What are Langerhans cells and where are they found?

Dendritic cells of bone marrow origin

Scattered throughout stratum spinosum

68

What is the function of Langerhans cells?

Present antibodies to T lymphocytes

Mediate immune reactions (Eg allergic contact dermatitis)

69

What is significant about the staining properties of melanocytes and Langerhans cells?

Difficult to see without special stains

70

Where is the dermo-epidermal junction and what does it consist of?

Just below the stratum basale

Basement membrane

71

What stain is used to best see the dermo-epidermal junction?

PAS

72

What are the constituents of the Dermis layer of skin?

Fibroblasts and extracellular matrix
Blood vessels
Lymph vessels
Mast cells
Nerves

73

What is the function of fibroblasts in the dermis?

Synthesise the extracellular matrix

74

What does the extracellular matrix of the dermis contain?

Collagens (especially type 1)
Elastin
Other extracellular matrix components

75

What is the main component of scar tissue?

Collagen

76

What is the result of excessive scar tissue production following wounding?

Keloids

77

Describe the form and distribution of blood vessels in the dermis?

Small blood vessels in the more superficial dermis
(Mainly capillaries, some small venules and arterioles)
Larger blood vessels in the deeper dermis

78

How do birthmarks arise?

Congenital malformation of dermis blood vessels

79

Where are mast cells found in the dermis?

Distributed around blood vessels

80

What is the major significant secretory product of mast cells in the dermis?

Histamine

81

What is the result of histamine release from mast cells in the dermis?

Increased vascular permeability leading to plasma leakage into dermis.

This results in localised oedema that causes urticaria (hives) and angio-oedema in the skin.

82

What is the function of nerves in the dermis?

Sensory nerves transmit sensation

83

Name the various skin appendages found in the dermis

Hair follicles and sebaceous glands (Pilosebaceous unit)
Sweat glands
Nails
Immediate subcutaneous fat (adipose tissue)

84

What type of glands are sebaceous glands and what type of secretion do they utilise?

Branched acinar

Holocrine secretion

85

What is the clinical significance of the sebaceous duct in a Pilosebaceous unit?

Acne obstructs flow of secretions through this duct onto hair

86

What are the two types of sweat glands?

Eccrine (merocrine)

Apocrine

87

What is the function of Eccrine sweat glands?

Where are they found?

How are they controlled?

Major sweat glands found in most areas of the body

Produce a clear, odourless secretion of water and NaCl (NaCl reabsorbed in duct to reduce salt loss)

Active in thermoregulation

Controlled by the hypothalamus

88

Describe the composition of an Eccrine sweat gland

Intra-epidermal spiral duct
Straight dermal portion of duct
Coiled acinar secretory portion in the dermis

89

Where are Apocrine sweat glands most abundant?

Axillae
Genitals
Submammary area

90

What is the function of Apocrine sweat glands?

Produce odourless, protein rich secretions
This function is of no discernible value

91

How is body odour produced?

Digestion of protein rich secretions from Apocrine sweat glands by cutaneous microbes

92

What are the main functions of the skin?

Barrier
Sensation
Thermoregulation
Pychosexual communication

93

Describe the barrier function of the skin.
How is this relevant to drug administration?

Give an example of a disease that might disrupt the barrier function.

Stratum corneum forms a major barrier preventing percutaneous absorption of exogenous substrates

The barrier must be overcome during percutaneous absorption of drugs

Barrier may be seriously disrupted by Psoriasis.

94

Describe the Sensory function of the skin.

Sensory nerves of the skin allow a sense of:

Temperature
Touch
Tissue damage (Pain)

95

Give two examples of diseases that affect the sensory function of the skin.

Leprosy - Disease of the peripheral nerves

Diabetic sensory neuropathy

96

What are the two methods of thermoregulation employed by the skin

Vascular thermoregulation
Thermoregulatory eccrine sweating

97

What are the twin processes involved in vascular thermoregulation and the consequences of each?

Dilation of skin blood vessels:
Leads to heat loss

Constriction:
Leads to pallor and heat conservation

98

How is eccrine sweating involved in thermoregulation?

Evaporation of eccrine sweat leads to cooling

99

How is the skin involved in psychosexual communication?

Appearance manipulated as a means of communication or expression (Eg Tattoos and piercings)

100

Describe the how Psoriasis leads to it's characteristic scaled appearance

Extreme proliferation of stratum basale cells Causing gross thickening of Stratum spinosum and excessive stratum corneum production

Hence leading to the characteristic excess scaling of the skin

101

What proportion of the population experiences Psoriasis in their lives?

2%

102

What is the cause of Psoriasis?

Exact cause not known

However, it runs in families and so is influenced by genetic factors.

103

What cells are associated with a malignant melanoma?

Tumour of melanocytes

104

How is the dermo-epidermal junction significant to maligant melanoma prognosis?

Superficial spreading melanoma doesn't penetrate the basement membrane and is associated with a good prognosis

More penetrating 'nodular' melanomas are associated with a very poor prognosis

105

What makes malignant melanomas hard to spot in a clinical environment?

The look like moles (benign growths of melanocytes)

106

What is Alopecia areata?

An autoimmune attack on hair follicles causing hair loss

107

What is Vitiligo?

An autoimmune disease in which the immune system attacks melanocytes causing areas of de-pigmentation

108

What is significant about the distribution of Vitiligo?

Usually occurs in symmetrical, localised areas

No known cause for this, possibly under neural control as melanocytes are derived from the neural crest