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TOB > Session 5 > Flashcards

Session 5 Flashcards

0
Q

What are the functions of connective tissue?

A
  • Provides substance and form to the body and organs
  • Provide a medium for diffusion of nutrients and wastes
  • Attach muscle to bone and bone to bone
  • Provides a cushion between tissues and organs
  • Defends against infection
  • Aids in injury repair
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1
Q

Define connective tissue and give examples

A
  • Is found in a continuum throughout the body connecting muscle, nervous and epithelial tissue in a structural way, but also provides metabolic and physiological support
  • Blood (gas transport and immune defence functions)
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2
Q

What is connective tissue made up of?

A
  • Cells
  • Extracellular matrix: ground substance (hyaluronate proteoglycan aggregates) and fibres (collagen, reticular and elastic)
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3
Q

How do connective tissues differ?

A
  • Type of cells contained
  • Abundance/density of cells
  • Constitution of extracellular matrix: ground substance composition; fibre type, abundance and arrangement
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4
Q

What are the types of embryonic connective tissue?

A
  • Mesenchyme

- Mucous

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5
Q

What types of regular/proper connective tissue are there?

A
  • Loose/areoles

- Dense: regular; irregular

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6
Q

What are types of specialised connective tissue?

A
  • Adipose Tissue
  • Blood
  • Bone
  • Cartilage
  • Haemopoietic tissue
  • Lymphatic tissue
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7
Q

Where does Mesenchyme cells come from?

A
  • Proliferation and Migration of Mesodermal cells of the Middle germ layer (and a few ectoderm all cells)
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8
Q

What happens to the mesenchyme cells?

A
  • Maturation and proliferation produces various connective tissue (eg cartilage, adipose, ligaments, tendons, bone and skeletal muscle), serous membranes, vascular and Urogenital systems and muscle
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9
Q

What type of cells does Mesenchyme consist of?

A
  • Multipotent progenitor cells
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10
Q

What type of Mesenchyme cells are in the adult?

A
  • Pluripotent cells that can produce new connective tissue cells for healing
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11
Q

What type of connective tissue is in the umbilical cord?

A
  • Mucous connective tissue makes up the Wharton’s jelly
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12
Q

Explain the structure of the hyaluronate proteoglycan aggregate in the ground substance

A
  • Hyaluronic acid molecules have many proteoglycan monomers attached, which themselves are made up of a core protein with glycosaminoglycan (GAG) units attached
  • The high density of negative charges on the GAGs attract water, forming a hydrated gel
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13
Q

Give examples of types of collagen

A
  • Type I:most widely distributed; fibres aggregate into fibres and fibre bundles (eg in tendons, capsules of organs and skin dermis)
  • Type II: Fibrils do not form fibres (in hyaline and elastic cartilage)
  • Type III (Reticulin): Fibrils form fibres around muscle and nerves cells and within lymphatic tissues and organs
  • Type IV: Unique form present in basal Lamina of Basement membrane
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14
Q

What are fibroblasts?

A
  • Secrete procallagen from which collagen fibrils are assembled and are associated with the fibroblasts
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15
Q

What type of connective tissue is in the testis capsule?

A
  • Dense irregular
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16
Q

What type of fibres are in a lymph node?

A
  • Capsule contains collagen bundles
  • Reticular fibres (collagen type III)
  • Also contain lymphocytes
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17
Q

What are elastic fibres?

A
  • Elastin is the main component of elastic fibres which is itself surrounded by microfibrils called fibrillin
  • Occurs in most connective tissue but varies (eg is important in the dermis, artery walls and sites with elastic cartilage
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18
Q

What is Marfan’s syndrome?

A
  • An autosomal dominant disorder in which expression of the fibrillin gene is abnormal, causing the elastic tissue to be abnormal
  • Sufferers are abnormally tall, exhibit arachnodactyly (abnormally long and slender fingers), have frequent joint dislocations and can be at risk of catastrophic aortic rupture
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19
Q

Describe the structure of a small elastic fibre

A
  • Tunica intima (indistinct endothelial cells) (lumen side)
  • Tunica media (elastin lamellae)
  • Tunica adventitia (collagen) (outside)
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20
Q

Describe the structure of the aorta wall

A
  • Tunica intima (thin layer)
  • Tunica media (thick layer with many elastic lamellae): contains smooth muscle cells which produces elastin, collagen and extracellular matrix
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21
Q

Describe the structure of a mammary gland (masson’s trichromatic)

A
  • Glandular epithelium
  • Loose irregular connective tissue (wispy collagen and many fibroblasts)
  • Dense irregular connective tissue (thicker and more abundant collagen and fewer fibroblasts)
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22
Q

What type of connective tissue is in the Submucosa eg in the colon?

A
  • loose
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23
Q

What is contained in loose connective tissue?

A
  • Branching elastic fibres
  • Collagen fibres
  • Small blood vessel
  • Nuclei of fibroblasts
  • Mast cells
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24
Q

What type of connective tissue is the dermis?

A
  • Dense irregular
  • Bundles of collagen are densely packed but irregular arranged
  • Can resist forces in multiple directions to prevent tearing
  • Elastic fibres allow a degree of stretch and restores the original shape
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25
Q

What are capsules?

A
  • Protect tissues that the connective tissue surrounds (eg adrenal gland, spleen, ovary, testis, prostate, joint)
  • Type of Connective tissue varies depending on location from loose to dense irregular
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26
Q

What type of connective tissue makes up the tendon?

A
  • Dense regular
  • connects muscle to bone
  • parallel densely packed collagen bundles with rows of elongated flattened fibroblasts between them
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27
Q

Describe the structure of myotendinous junctions

A
  • Skeletal muscle fibres interdigitate with tendon collagen bundles
  • Sarcolemma always lies between the collagen bundles and the muscles’s myofilaments
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28
Q

Describe the structure of a short ligament

A
  • Connects bone to bone
  • Collagen bundles densely packed in parallel arrangement, are arranged in fascicles surrounded by loose connective tissue
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29
Q

What cells are commonly found in connective tissue?

A
  • Fibroblasts
  • Macrophages
  • Mast cells
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30
Q

What is the function of fibroblasts?

A
  • Synthesis and secrete ground substance and fibres that are in the ground substance
  • Important in wound healing, are primarily responsible for the formation of scar tissue
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31
Q

Where do macrophages come from?

A
  • Blood monocytes which move into loose connective tissue, especially when there is local inflammation
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32
Q

What is the function of macrophages?

A
  • Are phagocytic: degrade foreign organisms and cell debris

- Are ‘professional antigen presenting cells’: present foreign material to T lymphocytes of the immune system

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33
Q

Where are mast cells found?

A
  • Connective tissue near blood vessels

- Not found in CNS to prevent damaging effects of odema there

34
Q
  • What do mast cells contain?
A
  • Abundant granules which contain:
    ~ Heparin (anticoagulant)
    ~ Histamine (increases permeability of blood vessel walls)
    ~ Substances that attract eosinophils and neutrophils
    (part of immune system)
35
Q

What is the function of mast cells?

A
  • Are coated with Immunoglobulin E (IgE) (molecules that specifically bind allergens)
  • The contents of the granules are rapidly released from the cell when an allergen cross-links with the surface-bound IgE molecules
  • Granule secretions can result in immediate hypersensitivity reactions, allergy and anaphylaxis
36
Q

How do adipose tissue cells develop?

A
  • Mesenchymal cells develop into fibroblasts or preadipocytes (early lipoblasts)
  • The early lipoblasts develop numerous lipid droplets in their cytoplasm
  • In brown adipocytes the multiple lipid droplets remain separate, but in a mature lipoblasts (white adipocyte) the multiple lipid droplets fuse to form a single droplet that displaces all cell content to the cell periphery
37
Q

Why do white adipocytes look empty in H&E stains?

A
  • Toluene and xylene have dissolved the lipid
38
Q

What is the function of white adipocytes?

A
  • Contain fats which acts as a: fuel reserve; thermal insulator and shock-absorber
39
Q

Where are brown adipocytes found?

A
  • Near to scapula, sternum and axillae (especially in newborns)
  • Also present in upper chest and neck of adults
40
Q

What is the function of brown adipocytes?

A
  • High respiratory capacity for the generation of heat (further promoted by uncoupling oxidative phosphorylation) as there is a rich vascular supply and abundant mitochondria
  • Non-shivering thermogenesis is important for babies and hibernating animals
41
Q

What are some variations in the macroscopic structure of human skin?

A
  • Colour: Ethnicity; Site (lips,areole); UV exposure
  • Hair: Site (hairy vs hair-free areas eg palms, soles, lips); Sex (facial and more profuse body hair growth in men); Age (baldness in men, greying in both sexes); Ethnicity (colour, character)
  • Laxity/Wrinkling: Site; Age; Ultraviolet exposure
  • Oiliness: Puberty; Site
42
Q

How do some macroscopic variations of skin influence the susceptibility to and/or manifestations of skin disease?

A
  • Vitiligo: psychosocial impact if it affects visible areas of darker-skinned individuals; less of a problem in fair-skinned people as not so visible
  • Alopecia areata/Alopecia totalis (autoimmune response leading to hair loss): more psychosocial impact if it affects scalp, especially in women
  • UV induced abnormalities: fair skinned people more susceptible to sunburn, freckling, ageing and skin cancer (eg basal cell carcinoma and malignant melanoma) especially in individuals with red hair
  • Acne: more common during puberty
43
Q

Describe the structure of the epidermis

A
  • Consists of stratified squamous keratinised epithelium, made up of keratinocytes and their products
  • Layer:
    ~ Horny layer (stratum corneum)
    ~ Granular layer (stratum granulosum)
    ~ Prickle cell layer (stratum spinosum)
    ~ Basal layer (stratum basale)
44
Q

What happens in the basal layer?

A
  • Keratinocytes mitosis

- Keratinocytes then move upwards to the prickle cell layer

45
Q

What happens in the prickle cell layer?

A
  • Terminal differentiation begins and keratinocytes loose thei ability to divide
  • Keratinocytes synthesise keratinocytes (hetrodimeric fibrous protiens) which contribute to the strength of the epidermis, also the main constituent of hair and nails
46
Q

What abrupt changes occur in the granular layer?

A
  • Keratinocytes lose their plasma membrane (phospholipid bi layer)
  • Keratinocytes begin differentiating into corneocytes (main cells of horny layer/stratum corneum)
47
Q

What does the granular layer contain?

A
  • Keratohyalin granules, which are aggregates of:
    ~ Keratins
    ~ Other fibrous proteins (eg filaggrin, involucrin)
    ~ Enzymes which: degrade phospholipid bilateral (phospholipase); cross-link proteins eg filaggrin (aggregates proteins), involucrin (forms a major part of corneocyte envelope)
48
Q

What is the structure and function of the horny layer (stratum corneum)?

A
  • Layers of flattened corneocytes

- Major role in skin barrier function (eg prevents loss of water-water barrier function)

49
Q

What is the transit time of a keratinocyte from the basal layer to the stratum corneum?

A
  • 30-40 days
50
Q

What other cells are in the epidermis?

A
  • Melanocytes

- Langerhans cells

51
Q

What are malanocytes?

A
  • Dendritic cells of neural crest origin
  • Occur at intervals along basal layer of epidermis (1/5 to 8 cells)
  • Difficult to see histologically without special stains
  • Produce melanin (pigment that gives skin colour)
  • In dark-skinned individuals produce more melanin but are not increased in number
52
Q

What are Langerhans cells?

A
  • Dendritic cells of bone marrow origin
  • Scattered throughout prickle cell layer
  • Difficult to see histologically without special stains
  • Highly specialised capacity to present antigens to T lymphocytes
  • Mediates immune reactions eg allergic contact dermatitis
53
Q

How is melanin transferred to neighbouring keratinocytes?

A
  • Pigment donation: Phagocytosis of tips of dendritic processes to transfer mature melanosomes (organelles containing melanin)
54
Q

How are prickle cells joined?

A
  • Prickle-like desmosomes (intercellular junctions)
55
Q

What are some disorders of epidermal components?

A
  • Psoriasis (abnormal epidermal growth and differentiation)
  • Allergic contact dermatitis (mediated by Langerhans cells)
  • Malignant melanoma (malignant growth of malanocytes)
  • Vitiligo (Autoimmune destruction of melanocytes)
56
Q

What is psoriasis?

A
  • Common skin disease (affects 2% of population)
  • Cause unknown, but runs in families so is influenced by genetic factors
  • Extreme proliferation of epidermal basal layer, causing gross thickening of prickle cell layer and production of excessive stratum corneum cells
  • Manifests clinically as excessive scaling
  • Can affect any area of the skin (can cover entire body surface)
57
Q

What is malignant melanoma?

A
  • An aggressive malignant tumour (neoplasm) of melanocytes, most commonly found in the skin
  • Superficial spreading melanoma (tumour cells above epidermal basement membrane) has a good prognosis while penetrating, nodular melanomas have a poor prognosis
  • Common moles are benign growths of melanocytes but can be difficult to distinguish from melanomas clinically
58
Q

What is vitiligo?

A
  • Autoimmune disease where the immune system attacks malanocytes, usually in symmetrical, localised areas of the skin causing depigmentation
  • Is more visible in dark skin
  • No explanation for symmetrical nature - could be under neural control as melanocytes are derived embryologically from neural crest
59
Q

What is Alopecia areata?

A
  • Autoimmune attack on hair follicles
60
Q

Where is the dermo-epidermal junction? (Basement membrane zone)

A
  • The epidermal basement membrane at the dermo-epidermal junction is below the basal layer of the basal layer of the epidermis
  • Best seen with a PAS stain
61
Q

What is the dermis?

A
  • Dense irregular connective tissue
  • Tough, fibrous and vascular layer
  • Main component of leather
62
Q

What does the dermis consist of?

A
  • Extracellular matrix: collagen (especially type I); elastin; other extracellular matrix components
  • Fibroblasts (synthesise extracellular matrix)
  • Blood vessels
  • Lymphatic vessels
  • Mast cells
  • Nerves
63
Q

What can damage to collagen and elastin in the dermis cause?

A
  • Solar elastosis (excessive UV exposure)
  • Stretch marks (eg pregnancy)
  • Keloids (excessive scar tissue following wounding - consists of mainly collagen synthesised by fibroblasts)
64
Q

What are birthmarks (port wine stain) caused by?

A
  • Congenital malformation of dermal blood vessels
65
Q

Where are tissue mast cells found in the skin?

A
  • Around dermal blood vessels
66
Q

When and what happens when mast cells are activated?

A
  • Type I immediate hypersensitivity (allergic) reactions
  • Histamine is released
  • Causes increased vascular permeability and leakage of plasma into extravascular sites
  • Causes local oedema (swelling due to increased tissue fluid)
  • In skin can cause urticaria and angio-oedema
  • May have serious consequences in vital structures eg Upper respiratory tract
67
Q

Describe the layout of blood vessels in the dermis

A
  • Small blood vessels in the superficial dermis (mainly capillaries, small venules and arterioles)
  • Larger blood vessels in the deeper dermis
68
Q

Give examples of skin appendages

A
  • Hair follicles ) pilosebaceous
  • Sebaceous glands ) unit
  • Sweat glands (eccrine (merocrine)/appocrine)
  • Nails
69
Q

What type of secretion is used by sebaceous glands?

A
  • Holocrine
70
Q

What is acne?

A
  • Skin disease affecting sebaceous glands
71
Q

What is acne caused by?

A
  • Abnormal differentiation of sebaceous gland ducts which become obstructed
  • Increased sebum production
  • Infection with normally harmless skin bacteria
72
Q

Why does acne normally occur on the face?

A
  • Most abundant location of sebaceous glands
73
Q

What are eccrine sweat glands?

A
  • Major sweat glands of the body
  • Use eccrine/merocrine secretion
  • Found in most of skin
  • Produce a clear, oderless substance consisting of water and NaCl (NaCl is reabsorbed in the duct to reduce salt loss)
  • Active in thermoregulation and are controlled by the hypothalamus
74
Q

What do eccrine glands consist of?

A

(Cuboidal epithelial cells)

  • Intraepidermal spiral duct (acrosyringium)
  • Straight dermal portion
  • Coiler acinar portion in dermis
75
Q

What is hyperhydrosis?

A
  • Increased sweating
  • Cause usually unknown
  • May effect only palms and soles
76
Q

What are apocrine sweat glands?

A
  • Large sweat glands most abundant in axillae, genital and submammary areas
  • No function of value
  • Produce an oderless, protein-rich, apocrine secretion
  • Digestion of this by cutaneous microbes causes body odour
77
Q

What are the main functions of skin?

A
  • Barrier function
  • Sensation
  • Thermoregulation
  • Psychosexual communication
78
Q

What is the barrier function of the skin?

A
  • Outer epidermis (stratum corneum) forms a barrier preventing percutaneous absorption of exogenous substrates
  • Much studies as must be overcome in the percutaneous absorption of drugs
  • May be seriously disrupted by many disease eg psoriasis
79
Q

What does a poor barrier function lead to?

A
  • Loss of fluid
  • Loss of protein
  • Loss of other nutrients
  • Loss of heat
  • Excessive absorption of
    potential harmful exogenous
    agents eg drugs
80
Q

What is the sensation function of the skin?

A
  • Sensory nerves in the skin allow sense of touch, temperature, tissue damage
  • Affected by leprosy (disease of peripheral nerves) and diabetic sensory neuropathy
81
Q

What is the thermoregulation function of the skin?

A
  • Vascular thermoregulation (dilation/constriction of blood vessels) and thermoregulatory eccrine sweating (evaporation of eccrine sweat causes cooling) are critically important in maintenance of body temperature
  • Failure of either can have serious consequences
82
Q

What happens if vascular thermoregulation fails?

A
  • Widespread vasodilation of erythrodermic psoriasis and the inability to vasoconstrict in a cold environment leads to heat loss
  • Patients are often shivery and may become hypothermic
84
Q

What is the psychosexual function of the skin?

A
  • Skin and its appearance are manipulated as a means of communication and expression eg tattoos and piercings

TOB (12 decks)

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