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MCD > Epithelial Cells and Tissues > Flashcards

Epithelial Cells and Tissues Flashcards

1
Q

What are the contents of the nucleus?

A

Nucleoplasm, nucleolis, and chromatin. Heterochromatin is the less active DNA.

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2
Q

What are the densities of the large and small subunits in the prokaryotic ribosome?

A

Small subunit is 30s, large subunit is 50s, and the total ribosome is 70s

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3
Q

What is the density of the large and small subunit of the eukaryotic ribosome?

A

Small subunit is 40s, large subunit 60s and total ribosome 80s.

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4
Q

What is the nuclear lamina and what is it involved in?

A

The specialised type of cytoskeleton that has developed on the internal surface of the nuclear envelope - important for assembly and disassembly of the nuclear envelope in cell division.

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5
Q

How can the rough ER and smooth ER be described as?

A

Rough ER is granular, smooth ER is agranular.

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6
Q

What are the functions of the SER?

A

Detoxification and lipid metabolism - also a storage of Ca2+ ions in the cells (important in cell signalling).

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7
Q

What are peroxisomes and what do they do?

A

Membrane bound organelles that contain enzymes involved in lipid and oxygen metabolism, the enzymes can crystallise to form the cores that are observed in TEM. Enzymes include oxidised, catalases and peroxidases.

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8
Q

What is the function and structure of microtubules?

A

Polymers of a and B tubulin heterodimers (two protein monomers) that are 20nm thick. They act as tracks for motor proteins, and are a component of the cilia and flagella. Also act as spindle fibres in mitosis.

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9
Q

What is the structure of cilia and flagella?

A

Microtubules are present in the 9 + 2 formation. Attached to ATP dependent motor proteins that distort the cilia or flagella to cause movement.

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10
Q

Where do microtubules originate from?

A

microtubule organizing center (MTOC)

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11
Q

What are the intermediate filaments present in epithelia?

A

Cytokeratins

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12
Q

What are the intermediate filaments found in mesenchymal cells?

A

Vimentin

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13
Q

What are the intermediate filaments found in neurones?

A

Neurofilament protein

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14
Q

What are the intermediate filaments found in muscle cells?

A

Desmin

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15
Q

What is the function of intermediate filaments?

A

Give mechanical strength to the cell, and connect cells together through the desmosomes. Nuclear lamins are intermediate filaments integrated in the nuclear envelope which stabilises the envelope.

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16
Q

What are microfilaments and what is their function?

A

Monomer of globular actin, and polymer of filaments actin. Gives the cell its shape and allows it to contract and expand (eg. Muscle cells/mitosis). Can be associated with myosin in the sarcomere. Associate with the adhesion belts in epithelia or epithelium.

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17
Q

What are the main cell types?

A

Connective, contractile, epithelial, haemopoietic, and neural.

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18
Q

Give some examples of connective tissue cells

A

Fibroblasts, chondrocytes (cartilage), osteocytes (bone).

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19
Q

Give some examples of contractile tissues.

A

Skeletal muscle, cardiac muscle, smooth muscle

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20
Q

Give some examples of haemopoietic cells

A

Blood cells, tissue-resident immune cells, bone marrow cells

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21
Q

Give some examples of neural cells

A

Neurones and glial cells (support cells)

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22
Q

What are epithelial cancers called?

A

carcinomas

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23
Q

What are mesenchymal cancers called (connective tissue and muscle)?

A

Sarcomas

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24
Q

What are haematopoietic cancers called?

A

Lymphomas (from lymphocytes) and leukaemia (from bone marrow cells).

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25
Q

What are neural cell cancers called?

A

Neuroblastomas (in neurones) or gliomas (from glial cells).

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26
Q

Define a tissue.

A

A group or groups of cells whose type, organisation and architecture are integral to its function.

27
Q

What are tissues made up of?

A

Cells, extracellular matrix and fluid

28
Q

What is the extracellular matrix?

A

Material deposited by cells that form the ‘insoluble’ part of the extracellular environment.

29
Q

What is the extracellular matrix made of?

A

Consists of fibrillar proteins (collagens/elastins) in a hydrated gel (proteoglycans/ground substance).

30
Q

What are the two forms of cell-cell junctions?

A

Zonulae (belts) and maculae (spots).

31
Q

How are cell cell junctions arranged in epithelia?

A

The apical junctional complex contains a tight junctions nearest the apex, then an adherent junction just below and then desmosomes scattered around the lateral membrane.

32
Q

What do gap junctions do?

A

Act as regions of direct communication between adjacent cells.

33
Q

What are tight junctions¬ and what is their function?

A

Zonula occludens (belt junctions). Points on the adjacent membranes that form close contacts - they form a network of contacts, the more elaborate the tighter the seal. They act to seal paracellular pathways (gate function) and segregate the apical and basolateral membrane (fence function).

34
Q

What is the adhesion belt and what is it’s function?

A

Also known as adherens junction or zonula adherens, it forms just nasal to the apical tight junction. Caderin is the transmembrane adhesion molecule that holds cells together and associate with the actin cytoskeleton. Controls the assembly of other junctions.

35
Q

What are desmosomes and what is their function?

A

Macula adherens, which are found at multiple spots between cell membranes. Contains a cadherin like molecule which links to intermediate filaments - provides mechanical continuity between cells.

36
Q

What are gap junctions¬ and what is their function?

A

Macula communicans, which are made of clusters of pores formed from 6 identical subunits in the membrane. The pores are continuous with those adjacent. Allows the passage of ions and small molecules between cells, they can be opened and closed by pH or ion concentrations. They are known as the electrical synapse, important in the passage of electrical signals in some tissues.

37
Q

What is the chemical synapse?

A

Mainly in neural tissue, button like junctions between neurones which uses a variety of receptors and chemical signals.

38
Q

What are simple squamous epithelial tissue and where is it found?

A

Simple means a single cell layer, while squamous means a flattened shape. Found in the alveoli and endothelium lining the blood vessels.

39
Q

What is simple cuboidal epithelial tissue and where is it found?

A

Single cell layer where cells are approximately cube shaped - line the kidney collecting duct.

40
Q

What is simple columnar epithelial tissue and where is it found?

A

Single cell layer that is pillar shaped, found in enterocytes (intestine) and other absorptive and secretory epithelia.

41
Q

What is stratified squamous epithelial tissue and where is it found?

A

Multiple layers where the top layer has a flattened shape, can be keratinising (skin - nuclei not visible in surface cells) or non-keratinising (vagina, anus, mouth - nuclei visible in surface cells)

42
Q

What is pseudostratified epithelium and where is it found?

A

Falsely stratified, all surface cells have contact with basal lamina. Found in the trachea and bronchi, and ducts in the urinary/reproductive tracts.

43
Q

Why are epithelial cells polar?

A

As most functions are directional, eg. Secretion and absorption.

44
Q

How do epithelial cells become polar?

A

Junctions separate the cells into the apical domain and the basolateral domain, which have different compositions and functions.

45
Q

What is the basolateral membrane?

A

Basal membrane is the membrane with contact to the extracellular matrix, the lateral membrane is the side.

46
Q

How do tight junctions establish polarity?

A

They prevent the mixing of proteins and lipids between different plasma membrane compartments.

47
Q

How are transporting epithelial cells structured?

A

The nucleus is basal, with many mitochondria at the basal membrane unfolding which provides ATP for the many active transporters present.

48
Q

What is the function of microvilli?

A

They increase the SA of the plasma membrane to make absorption more effective.

49
Q

When active transport of glucose occurs¬ why is the gradient not lost by back diffusion between cells?

A

Tight junctions seal the paracellular pathway, allowing concentration gradients to be made and allowing cell membranes to control the passage of glucose - via the distribution of transport proteins.

50
Q

How are exocrine secretory epithelial cells laid out?

A

Secretory granules at the top, nucleus and Golgi at the basolateral area. Often arranged into glands.

51
Q

How are endocrine secretory epithelial cells laid out?

A

Nucleus and Golgi apparatus at the top, with the secretory geniuses in the basal cytoplasm - as the compounds are secreted into the bloodstream.

52
Q

What are the three layers of the skin?

A

Epidermis, dermis, and hypodermis.

53
Q

What occurs if there are defects in the cytokeratins or cell junctions?

A

Blistering occurs - as there is a damage of epidermal cells. Desmosomes provide mechanical stability to tissues - therefore, if they are broken down the epithelia are easily damaged.

54
Q

What is the process of epithelial turnover in the small intestine?

A

The crypts of Leiberkhun contains stem cells in their mid-region that produce new epithelial cells. These cells then migrate up to the epithelium as the cells are lost from the villus tip (cell turnover).

55
Q

What are the crypts of Lieberkuhn?

A

Intestinal glands.

56
Q

How does chemotherapy affect cell turnover?

A

Stops cell division in the crypts of Leiberkhun, therefore the villi shorten as cells are lost but not replaced.

57
Q

What occurs when there is too much cell proliferation in the colon?

A

An adenoma forms - benign tumour with a risk of cancer.

58
Q

What is the process of cell turnover in the epidermis?

A

Surface cells are constantly lost, but replaced by new cells formed in the basal layer which migrate up while also differentiating to become flattened and keratinised.

59
Q

When are changes to the steady state of cell turnover normal?

A

Menstrual cycle in females and increase in epithelial glands in the breast of pregnant women (and the loss after weaning).

60
Q

How do calluses form?

A

The skin is irritated and pressure is applied. This simulates cells to divide rapidly and loss from the surface is less than rate of cell production, so there is an increase in tissue mass. Your skin adapts to changes in circumstances.

61
Q

How do warts form?

A

Warts form when the epidermal keratinocytes are infected by the human papilloma virus, which hijacks cell proliferation causing it to increase.

62
Q

What cells are present in the intestinal villi epithelium?

A

Enterocytes (absorptive), and goblet cells (secrete mucus).

63
Q

Which organelle type is abundant in the cells whose main function is secreting hormones?

A

Smooth endoplasmic reticulum.

MCD (56 decks)

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