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Tissues of the Body > Lecture 2.2: Glands > Flashcards

Lecture 2.2: Glands Flashcards

1
Q

How are glands classified?

A

Destination of secretion: Exocrine, Endocrine (some are mixed)

Method of secretion: Merocrine/Eccrine, Apocrine, Holocrine

Nature of secretion: Serous, Mucous

Organisation/Structure: Simple, Compound, Uni/Multicellular

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2
Q

Destination of secretion: Exocrine

A

These glands secrete their products through ducts

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3
Q

Destination of secretion: Endocrine

A

Ductless
Directly into blood

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4
Q

Method of secretion: Merocrine/Eccrine

A

Exocrine Glands only

Most glands are merocrine

The secretions of that cell are excreted via exocytosis from secretory cells into an epithelial-walled duct or ducts and then onto a bodily surface or into the lumen.

Producing a secretion that does not contain cellular components and is discharged without major damage to the secreting cell, no part of the gland is lost or damaged

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5
Q

Method of secretion: Apocrine

A

Exocrine Glands only

Mammary glands, anogenital region and axillae.

They bud their secretions off through the plasma membrane producing extracellular membrane-bound vesicles.

It loses part of its cytoplasm in their secretions.

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6
Q

Method of secretion: Holocrine

A

Exocrine Glands only

Sebaceous glands of the skin, Meibomian glands of the eyelid

Secretions are produced in the cytoplasm of the cell and released by the rupture of the plasma membrane, which destroys the cell and results in the secretion of the product into the lumen.

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7
Q

Nature of secretion: Serous

A

Produce a watery (protein rich) secretion

Stain intensely with H&E

Sweat Glands, Mammary Glands

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8
Q

Nature of secretion: Mucous

A

Mucous glands secrete a protein called mucin (highly glycosylated polypeptides) , which with water forms the substance known as mucus

Mucus is washed way during H&E staining, so mucous glands stain more poorly, leaving a ‘foamy’ appearance

Along whole digestive tracts

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9
Q

Organisation/Structure: Simple (Ducts)

A

Unbranched

Single duct

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10
Q

Organisation/Structure: Compound (Ducts)

A

Branched ducts

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11
Q

Acinar

A

Pear-like secretory portions with wide base and little inner free space

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12
Q

Tubular

A

Tube-like secretory portions

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13
Q

Goblet Cells

A

Unicellular Glands

Contain large Golgi in which new carbohydrates are added to newly-synthesised protein to create mucin

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14
Q

Colonic Crypts

A

Simple Tubular Glands

Resorption of water and electrolytes

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15
Q

Eccrine Sweat Glands

A

Simple coiled tubular glands

Secretory portions are surrounded by contractile “myoepithelial cells”

Their contraction transports luminal contents towards the ducts

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16
Q

Simple branched acinar galnds

A

Simple: Duct
Branched Acinar: Secretory Portion

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17
Q

Complex Glands: Features + Examples (acinar/tubular)

A

Branching Ducts so compound ductal sections
Glands of Brunner in the Duodenum
Exocrine Pancreas (compound tubular)
Salivary Glands (compound acinar)
Mammary Glands (compound tubuloacinar)

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18
Q

Intercalated Ducts

A

Join acini with larger collecting ducts

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19
Q

What is an acinus?

A

An acinus is any cluster of cells that resembles a berry

20
Q

Exocrine Pancreas

A

Complex Acinar Gland

The simple squamous epithelium of the intercalated ducts penetrates the pancreatic exocrine acini

21
Q

The Pancreas Gland Type

A

Mixed
Exocrine/Endocrine Gland

22
Q

Cystic Fibrosis and Sweat Ducts

A

In CF, the absence of the CFTR in the apical membranes of the epithelial cells of the sweat duct results in poor reabsorption of Cl-

This suppresses Na+ reabsorption

Cystic fibrosis and sweat testing for abnormally can confirm a diagnosis of CF

23
Q

Why was Cystic Fibrosis previously known as ‘Fibrocystic Disease of the Pancreas’?

A

In CF, exocrine secretions contain too little water

They become thickened, and block ducts

The exocrine pancreas becomes painfully inflamed (pancreatitis) and fibrotic

The gut receives insufficient pancreatic digestive enzymes, and malabsorption results

24
Q

When do symptoms of insufficient secretion of pancreatic digestive enzymes appear in CF?

A

Usually in the first year of life in 90% of cases

25
Q

Major Salivary Glands: Parotid Glands

A

Largest of the 3 main salivary glands

Complex Tubuloacinar Glands

Exclusively serous acini producing α-amylase

Ingestion of food stimulates the release of saliva via parasympathetic innervation

Strong sympathetic innervation leads to a dry mouth (xerostomia)

Striated ducts are important in Na+ resorption

26
Q

Major Salivary Glands: Submandibular Gland

A

2nd largest of the 3 main salivary glands

Mixed serous/ mucous gland

Striated ducts

Saliva is hypotonic, and striated ducts have membrane folds bearing transporters in their basal aspect to facilitate electrolyte resorption

In addition to producing a-amylase, serous cells produce lysozyme

27
Q

Major Salivary Glands: Sublingual Gland

A

Smallest of the 3 main salivary glands

Contains mainly mucous acini

28
Q

Mammary Gland: Structure + Functionality

A

Compound Tubuloacinar Gland

Myoepithelialcells assist secretion of milk from acini

Contraction of myoepithelial cells under control of oxytocin is experienced as ‘let-down’

29
Q

Mammary Gland: Apocrine Secretion

A

Non-membrane bound lipid pushes through the plasmalemma, covering droplets with membrane and a thin layer of apical cytoplasm

Membrane becomes transiently smaller, requiring addition of extra membrane

30
Q

Mammary Gland: Merocrine Secretion

A

Other milk constituents (e.g. lactose, proteins and minerals) are released by merocrine secretion

31
Q

Apocrine Sweat Glands

A

Whereas eccrine sweat glands are widely distributed, apocrine sweat glands develop at puberty

In the axillae, areolae of nipples, and genital and perianal regions

Confusingly, despite their name, these cells use merocrine secretion

32
Q

Thyroid Gland

A

Endocrine gland located anterior and inferior to the larynx

Active thyrocytes form a cuboidal epithelium that produces thyroxine (T4) and triiodothyronine (T3)

These hormones regulate basal metabolic rate

Parafollicular (or C cells) produce calcitonin (which slows bone turnover to reduce plasma calcium)

33
Q

Control of Thyroid Hormones

A

Release of thyroid hormones is under the endocrine control of thyroid stimulating hormone (TSH)

This is produced by the anterior pituitary

34
Q

Synthesis of Thyroid Hormones Brief

A

The tyrosine-rich glycoprotein thyroglobulin is synthesised by thyrocytes (thyroid follicular cells) and released by exocytosis into the colloid

35
Q

Synthesis of Thyroid Hormones

A

Tyrosine residues within the thyroglobulin molecule undergo iodination at one
or two positions

A diiodinated tyrosine residue is conjugated with a monoiodinated tyrosine
residue to create a pre-T3.

A diiodinated tyrosine residue is conjugated with another diiodinated tyrosine to create a pre-T4

The modified thyroglobulin molecule is endocytosed following TSH stimulation

Then undergoes proteolytic cleavage in lysosomes to release mature T3
and T4 molecules from the polypeptide chain

Thyroid hormones are released from the basal aspect of the cell by exocytosis and enter the bloodstream

36
Q

What is the most abundant Thyroid Hormone?

A

T4 is the most abundant and stable thyroid hormone

37
Q

What is the most metabolically active Thyroid Hormone?

A

T3

38
Q

How can T4 be converted to T3?

A

T4 can be converted to T3 in tissues by the removal of an iodine molecule via deiodinase action

39
Q

What happens when iodine is removed from T3?

A

Removal of a further iodine molecule creates inactive forms rT3 or T2

40
Q

Parathyroid Gland

A

Parathyroid hormone (PTH) secreted by principal cells stimulates bone resorption by osteoclasts.

This raises blood calcium levels

41
Q

Adrenal (Suprarenal) Glands

A

Adrenal glands are embedded in perirenal adipose near the superior poles
of each kidney

The adrenal cortex has three layers and secretes corticosteroid hormones

The medulla secretes adrenaline and noradrenaline

42
Q

Blood Supply to the Adrenal Gland

A

The adrenal medulla has a dual blood supply

It receives arterial blood from the medullary arterioles and venous blood from the capillaries of the cortex

Sinusoids allow maximum exchange of macromolecules

43
Q

Outer Cortex of the Adrenal Gland

A

The outer fibrous adrenal capsule provides protection

The zona glomerulosa produces mineralocorticoids such as aldosterone

The zona fasciculata produces glucocorticoids such as cortisol

44
Q

Inner Cortex of the Adrenal Gland

A

The zona reticularis produces weak androgens

The medulla produces adrenaline and noradrenaline

45
Q

Adrenal Secretions (4)

A

Mineralocorticoids: aldosterone regulates Na+ uptake by renal tubules

Glucocorticoids: cortisol regulates carbohydrate metabolism

Gonadocorticoids: weak androgens

Catecholamines: stress responses

Tissues of the Body (18 decks)

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