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Body Logistics > 4. Epithelial Cells > Flashcards

4. Epithelial Cells Flashcards

1
Q

What are mucous membranes?

A

Line certain internal tubes which open to the exterior.
Consists of epithelium lining lumen of a tube, adjacent layer of connective tissue (lamina propria)
Smooth muscle cells - muscularis mucosae

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2
Q

What are some examples of mucous membranes?

A

The GI tract, respiratory tract and urinary tract linings

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3
Q

What are serous membranes?

A

thin, two-part membranes lining closed body cavities
Envelope the viscera.
Secrete a lubricating fluid reducing friction.
Squamous epithelium secretes watering fluid.
Thin layer of connective tissue, attaches epithelium to adjacent tissues.

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4
Q

How do serous membranes develop?

A

Develop into bag-like cavity which they invaginate into. Become surrounded by cavity, not lying within it.
Outer wall parietal, inner wall visceral.
Visceral closest to organs in cavity, parietal outer edge.

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5
Q

Describe the structure of the pleurae of the lungs

A

Each lung has its own serosal membrane surrounding its surface.
Parietal pleura attached to inner layer of ribcage.
Visceral attached to parenchyma of the lung.
Serosal membrane releases moist pleura.
5ml of serum in each membrane.

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6
Q

Define epithelia

A

Sheets of contiguous cells, of varied embryonic origin, that cover the external surface of the body and line internal surfaces including the body’s vessels.

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7
Q

Where are epithelial tissues derived from?

A

From all embryological germ layers.
Ectoderm - epidermis
Endoderm - inner and outer linings of GI tract
Mesoderm - inner linings of body cavities

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8
Q

What surfaces contain epithelial linings?

A

Skin, GI respiratory and genitourinary tract,

pericardial, pleural sacs, peritoneum, blood vessels

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9
Q

What are the classifications of epithelial cell types?

A

Simple, one cell layer thick:
squamous, cuboidal, columnar, pseudostratified
Stratified/compound:
squamous, cuboidal, columnar, transitional

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10
Q

Describe the appearances of different simple epithelial tissues

A

Squamous - squished
Cuboidal - square
Columnar - tall, longer than wide (3x)

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11
Q

Describe the appearances of different stratified epithelial tissues

A

Squamous - several layers of squished
Cuboidal - square
Columnar - taller, longer than wide
Pseudostratified columnar - tall. nuclei are at different levels but still all directly attached to basement membrane
Transitional - different cell types, but characterised by cell type on top surface

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12
Q

What is the position, structure and function of the basement membrane?

A

Basement membrane = basal lamina

Sits below simple squamous epithelium

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13
Q

What are some examples of simple squamous epithelia?

A

Bowman’s capsule, lining vein, lung parenchyma

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14
Q

What are some functions of simple squamous epithelia?

A 
Fast material exchange and barrier to fluids
Barrier in the brain and CNS
Material exchange and lubrication
Barrier in Bowman's Capsule
Lubrication of lungs, heart and viscera
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15
Q

What are some examples of simple cuboidal epithelium?

A

A single layer of polygonal cells, height and width equal.
Lining of pancreatic duct, surrounded by connective tissue.
Bounds thyroid gland follicles.
Lining collecting ducts of the kidney - lots of basement membranes and connective tissue as barrier.

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16
Q

What are some functions of simple cuboidal epithelium?

A

Absorption and conduit (exocrine glands)
Absorption and secretion in kidney tubules
Barrier, Hormone synthesis and storage

17
Q

What are some examples of simple columnar?

A

Single layers of cells, heights greater than width.
Basement membrane has nuclei close to basal surface.
Lining the crypts of Lieberkuhn in intestinal glands.
Can contain microvilli - lining small intestine.

18
Q

What are some functions of simple columnar?

A

Absorption in small intestine and colon
Secretion in stomach lining and gastric glands
Lubrication in small intestine and colon

19
Q

What are some examples of pseudostratified epithelia?

A

Epithelia in which all cells make contact with the basement membrane, but not all cells reach surface.
Nuclei lie at different levels.
Upper respiratory tract, above basement membrane and connective tissue layers.
Lining of nasal cavity, trachea and bronchi.

20
Q

What are some functions of pseudostratified epithelium?

A

Secretion and conduit - respiratory tract
Mucus secretion
Particle trapping and removal

21
Q

What are some examples of stratified squamous epithelia?

A

Multiple layers of cells, outermost are squamous.
Non-keratinised lining vagina and oesophagus.
Part of anal canal, surface of cornea, inner eyelid.

22
Q

What are some functions of non-keratinised stratified squamous?

A

Protection against abrasion, reduces water loist, remains moist.
In the vagina, cells are rich in glycogen for lactobacilli maintaining low pH, destroys non-native bacteria.

23
Q

What is stratified squamous keratinised epithelium?

A

Outermost are squamous that have lost their nuclei and become squames of keratin.
Epidermis of skin is primarily this epithelium.
Outermost dead cells known as stratum corneum.

24
Q

What are some functions of the stratum corneum?

A

Stratum corneum layer greatly reduces water loss.
Prevents ingress of toxins, protects against abrasion.
Reduces microbial colonisation.

25
Q

Describe the structure of the skin.

A

Top layer is stratum corneum dead squames.
Epidermis - avascular epithelia epidermis.
Basement membrane, basal cells proliferating closest to membrane brown due to melanin.
Dermis - dense irregular connective tissue, made of collagen and elastin bundles in all directions.

26
Q

What are keratinocytes?

A

Stratified squamous keratinised epithelium is made up of mainly epithelial cells called keratinocytes.
Keratinocytes mitosis occurs in basal layer.
Daughter keratinocytes move towards surface, differentiate and lose ability to divide.
Keratinocytes synthesise keratins - strengthen epidermis.

27
Q

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

A

28-40 days

In diseases such as psoriasis, transit time is greatly reduced 2-4 days so stratum corneum is silvery scales.

28
Q

What other cells are present in the epidermis?

A

Melanocytes, intervals of 1:8 in basal layer.
Produce melanin, all have same number but some produce more than others (darker skin)
Melanocytes at basal layer, dendritic structure into cell.

Langerhans cells, highly specialised capacity to present antigens to T lymphocytes, mediate immune reactions.

29
Q

What are some functions of stratified squamous keratinised epithelium?

A

Protection against abrasion and physical trauma
Prevention of water loss
Prevention of microbial ingress
Shielding against UV light damage

30
Q

What is transitional epithelium?

Where is it found?

A

Surface cells vary in shape, different types.
Alter between a relaxed and stretched shape.
In urinary tract, proximal urethra at tip is keratinocytic.

31
Q

What are some functions of transitional epithelium within the urinary tract?

A

Distensibility, protection of underlying tissue from toxic chemicals

32
Q

What are some cell surface specialisations?

A

Keratin prevents water loss, protects against abrasion
Cilia controls micro-movement of luminal contents
Goblet cells - mucus secretions, moistens and lubricates.
Clara cells/club cells protect bronchioles and act as stem cells for respiratory epithelium.
Microfold cells, and stereocilia

33
Q

What are goblet cells?

A

On apical surface, no cilia present instead have microvilli.
Release mucins through exocytosis, water release increased by release of ions.
Nucleus at bottom of cell, secretory vesicles packed in containing mucin.
Epithelium of upper respiratory tract 9+2 actin and myosin arrangement.

34
Q

Describe the symptoms of cystic fibrosis

A

CTFR mutation - transmembrane conductance regulator
Deficiency of chloride ion release results in sticky immovable mucus.
Tissues that have mucins and cilia all affected, cannot use mucociliary escalator.
Airways - thick mucus, clogged airways, damages lungs
Liver - small bile duct blocked, disrupts digestion
Pancreas - zymogen secretions not released, digestion
Small Intestine - thick motile stools, can kill neonates
Reproductive tracts - absence of fine ducts, infertility
Skin - malfunctioning of sweat glands, salty sweat, crystals

35
Q

What are clara cells?

A

On the airway side of the terminal bronchioles, have club like apical surface, no cilia or basal bodies.
Protect bronchiolar epithelum.
Secrete products e.g. uteroglobin and surfactant.
Detoxify harmful substances in the lungs.
Contain P450 enzymes in SER.
Act as stem cell, to ciliated cells to regenerate epithelium.

36
Q

What are microfold cells?

A

Only in small intestine and close to lymphatic nodules.
Trap pathogens and other molecules.
Present these to underlying dendritic cells, that process material to lymphocytes and macrophaes in basal pocket.
Have a folded extension like a mushroom cap.
Represent a weak point as pathogens can enter here.

37
Q

What are stereocilia?

A

In the inner ear to respond to fluid motion for hearing and balance. Mechanosensing organelles of hair cells.
In epididymis and vans deferens - facilitate absorption of residual sperm body after spermiation complete.
Contain actin and myosin filaments, debated whether they can be involved in ejaculation.

38
Q

What are cell renewal rates within the lungs?

A

In the early stage, normal mucus layer thickens, cilia die off and ciliagenesis takes 2-4 days if stopped smoking.
Chronic stage - goblet cells and basal cells proliferate
Clara cells die and cannot regenerate.
Pneumocytes in alveoli die, fibroblasts lay down scar tissue.
Cells in trachea take 1-2 months, alveoli 8 days
Goblet cells take 10 days, clara cells always dead.

39
Q

What are some common respiratory conditions related to smoking?

A

Acute bronchitis - cough and mucus production, reduced lung function, excess mucus, swelling, inflammation
At later stages increased risk of serious respiratory diseases.
Chronic bronchitis - chronic inflammation, at least 2 episodes lasting 3 months, reduced lung function.
Irreparable damage to bronchioles and alveoli.
Emphysema - shortness of breath, permanent widening of airspace, destruction of air sacs.
Elastase destroys elastin, absence of alpha1 antitrypsin.
COPD - emphysema and chronic bronchitis, umbrella term
Asthma - wheeze, shortness of breath, chest tightness, due to bronchospasm, tightening of smooth muscle

Body Logistics (9 decks)

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