Epithelial tissues & glands Flashcards Preview

ESA 1 - Body Logistics > Epithelial tissues & glands > Flashcards

Flashcards in Epithelial tissues & glands Deck (30)
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1
Q

What is a gland?

A

Epithelial cell or collection of cells (epithelium invagination) specialised for secretion.

2
Q

According to what can glands be classified?

A
  1. Destination of secretion
  2. Gland structure
  3. Nature of secretion
  4. Method of discharge
3
Q

How are glands classified according to destination of secretion?

A
  1. Exocrine glands: have ducts to carry secretions to surface (e.g. Goblet cells secrete mucus from epithelium of upper respiratory tract)
  2. Endocrine glands: are ‘ductless’ but secrete directly into the bloodstream
4
Q

How are glands classified according to structure?

A
  • Can be: unicellular (e.g. Goblet cell) or multicellular.
  • Can be: tubular, acinar or alveolar.
  • Can be: coiled or branched.
5
Q

How can glands be classified according to method of secretion?

A
  1. Merocrine = exocytosis (vast majority of glands)
  2. Apocrine = secreted droplets covered by plasmalemma (e.g. Mammary gland - fat droplets in milk)
  3. Holocrine = whole cell breaks down, e.g. Sebaceous gland of skin undergoes holocrine secretion to fill hair follicle with sebum.
6
Q

What are the 3 major salivary glands?

A
  • Parotid
  • Submandibular
  • Sublingual
7
Q

Give an example of an organ that is both an exocrine and an endocrine gland.

A

The pancreas

  • endocrine cells in pancreatic ilets secrete insulin
  • exocrine cells in pancreatic acini secrete alkali and enzymes
8
Q

How does CF affect glands of patients?

A
  • Absence of CFTR in apical membrane of epithelial cells lining sweat gland ducts - poor reabsorption of chloride ions - sweat is rich in chloride and sodium ions (sweat testing for abnormally salty sweat).
  • Exocrine pancreas secretions thickened as contain too little water
    1) blocking of the ducts - exocrine pancreas painfully inflamed (pancreatitis) and fibrotic.
    2) gut receives insufficient pancreatic digestive enzyme - malabsorption.
9
Q

Skin is composed of which type of epithelium?

A
  • Stratified squamous epithelium (also found in oral cavity)
10
Q

What is the function of skin?

A
  • Protects against abrasion/physical trauma and pathogens
  • Prevents water loss
  • Shields against UV light damage
11
Q

Describe the layers of the skin epidermis.

A
  • Stratum corneum
  • Stratum granulosum
  • Stratum spinosum
  • Stratum basale
12
Q

Which cells are found in the skin epidermis?

A
  • Keratinocytes: synthesise keratins (heterodimeric fibrous proteins) which contribute to strength of epidermis).
  • Keratinocyte mitosis occurs mainly in basal layer. Daughter keratinocytes then move upwards to form stratum spinosum, where terminal differentiation begins and cells lose their ability to divide.
  • Stratum corneum = layer of dead keratinocytes.
13
Q

Apart from keratinocytes, which cells are found in the epidermis?

A
  • Melanocytes: dendritic cells of neural crest origin which occur at intervals along the basal layer of the epidermis. Produce melanin pigment.
  • Langerhans cells: dendritic cells of BM origin, scattered throughout prickle cell layer. Highly specialised capacity to present antigen to T lymphocytes. Mediate immune reactions, e.g. Allergic contact dermatitis.
14
Q

What is transitional epithelium and where is it found?

A
  • Found in bladder.
  • Specialised type of stratified epithelium that can stretch without breaking - from stratified cuboidal (empty bladder) to stratified squamous (full bladder)
15
Q

What are the functions of transitional (urinary) epithelium?

A
  • Distensibility

- Protection of underlying tissue from toxic chemicals

16
Q

What are epithelia?

A

Sheets of contiguous cells, of varied embryonic origin, that cover the external surface of the body (i.e. Skin) and line internal surfaces (e.g. GI, GU & resp tracts, blood & lymphatic vessels, pericardial & pleural sacs and peritoneum).

17
Q

What is the basement membrane?

A
  • Thin, flexible, acellular layer which lies between epithelial cells and the subtending connective tissue.
  • Consists of a basal lamina laid down by epithelial cells. Thickness can be augmented by a variably thick layer of reticular fibrils (type 3 collagen), elaborated by the subtending connective tissue.
18
Q

What is the function of the basement membrane?

A

1) Strong flexible layer to which epithelial cells adhere

2) Cellular and molecular filter

19
Q

What is the endothelium?

A

Simple squamous epithelium lining blood and lymph vessels.

20
Q

What is mesothelium?

A

Simple squamous epithelium lining body cavities - pericardium, pleura, peritoneum.

21
Q

Where can simple squamous epithelium be found?

A
  • Lining of blood and lymph vessels (endothelium)
  • Lining of body cavities - pericardium, pleura, peritoneum (mesothelium)
  • Pulmonary alveoli (gas exchange epithelium)
  • Bowman’s capsule and Loop of Henle (kidney)
22
Q

What are the functions of simple squamous epithelium?

A

(Good Nifflers Like Bright Accessories)

  • Gas and Nutrient exchange (endothelium and alveoli)
  • Lubrication (pericardium, pleura, peritoneum)
  • Barrier (Bowman’s capsule)
  • Active transport by pinocytosis (endo- and mesothelium)
23
Q

Where is simple cuboidal epithelium located and what is its function?

A
  • Thyroid follicles - hormone synthesis, storage & mobilisation
  • Small ducts of many exocrine glands - absorption & conduit
  • Surface of ovary - barrier/covering
  • Kidney tubules - absorption & secretion
24
Q

Where is simple columnar epithelium found and what is its functions?

A
  • Stomach lining & gastric glands - secretion
  • Small intestine & colon - absorption, secretion & lubrication
  • Gallbladder - absorption
  • Oviducts - transport (cells are ciliated), uterus
25
Q

Where is pseudostratified epithelium found?

A
  • Lining of conducting portion of respiratory system - nasal cavity, trachea & bronchi
26
Q

What are the functions of pseudostratified epithelium?

A
  • Secretion, e.g. Of mucus by Goblet cells
  • Conduit
  • Particle trapping and removal (are ciliated)
27
Q

Where can non-keratinised stratified squamous epithelium be found and what is the functions of this.

A
  • Located e.g.
    • Oral cavity
    • Larynx
    • Vagina
    • Surface of cornea and inner surface of eyelid
  • Functions:
    • Protection against abrasion
    • Reduced water loss but remains moist
28
Q

What is the difference between mucous and serous membranes?

A
  • Mucous membranes: line certain internal tubes which open to the exterior, i.e. The digestive, respiratory and urinary tracts. These mucosae bear mucus-secreting cells to varying degrees.
  • Serous membranes: thin, two-part membranes which line certain closed body cavities and envelop the viscera. Line the:
    • peritoneum (envelops many abdominal organs)
    • pleural sacs (envelop the lungs)
    • pericardial sac (envelops the heart)
      Secrete a lubricating fluid which promotes relatively friction-free movement of the structures they surround.
29
Q

What is a mucous membrane composed of?

A
  • An epithelium (type depends on site) lining the lumen of the tube.
  • An adjacent layer of connective tissue (lamina propria).
  • In the alimentary tract, a 3rd layer consisting of smooth muscle cells (muscularis mucosae).
30
Q

What does a serous membrane consist of?

A
  • Mesothelium: a simple squamous epithelium which secretes a watery lubricating fluid.
  • A thin layer of connective tissue (attaches the mesothelium to adjacent tissues and carries blood vessels and nerves).