Epithelia, Skin & Exocrine Glands Flashcards
What are two proteins found in the skin?
Keratin
Melanin
What is melanin?
A dark coloured light sensitive pigment protecting against excessive amounts of UV radiation.
What endocrine function does the skin carry out?
Vitamin D
What causes psoriasis? What does psoriasis result in? Particularly in which layers of the epidermis?
Increased production of skin cells. Red, flaky patches of skin. Stratum corneum
Which individuals are more at risk of vitamin D deficiency?
Dark skinned individuals
Vitamin D is produced in which reaction in the skin?
Reaction of 7-dehydrocholesterolwith UVb radiation
What can vitamin D deficiency result in?
Rickets
What individuals are at a higher risk of skin cancer? What is the reason for this?
Caucasians - in particular albinos
They lack skin pigmentation/melanin to protect from UV radiation
What are two types of membranes lining parts of the body?
Mucous
Serous
What do mucous membranes line?
Lines certain internal tubes which open to the exterior
Give an example of parts of the body that are lined by mucous membranes?
Alimentary tract
Respiratory tract
Urinary tract
What makes the mucous membrane mucousal?
It bares mucus-secreting cells to varying degrees
What 2 layers does a mucous membrane generally consist of?
Epithelium lining the tube Lamina propria (connective tissue)
What 3rd layer of the mucous membrane exists in the alimentary tract?
Smooth muscle cells —> muscularis mucosae
What do serous membranes line?
Closed body cavities
What is the structure of a serous membrane?
Thin
2 parts with lubricating fluid in between
Inside layer = visceral serosa
Outside layer = parietal serosa
What are the layers of a serous membrane?
1) A simple squamous epithelium mesothelium
2) A thin layer of connective tissue
What part of the serous membrane secretes the watery lubricating fluid?
The simple squamous epithelium (mesothelium)
Give 3 examples of serous membranes and the organs they each envelop.
The peritoneum - enveloping abdominal organs
The pleural sacs - enveloping the lungs
The pericardial sac - enveloping the heart
All epithelial tissue lies on top of …
A basement membrane and underlying connective tissue
What is the difference between simple and stratified epithelium?
Simple = one cell layer thick Stratified = more than 1 cell layer thick
What are 4 types of simple epithelium?
Squamous
Cuboidal
Columnar
Pseudostratified
What are 4 types of stratified epithelium?
Squamous
Cuboidal
Columnar
Transitional
What does a basement membrane consist of? What are its properties?
A basal lamina of type 4 collagen Reticular fibres (type 3 collagen)
A thin, flexible and strong layer for epithelia to adhere to
What is endothelium?
Simple squamous epithelium that lines all blood vessels
What is a mesothelium?
The epithelial lining closed body cavities (found in serous membranes) e.g. The pericardial sac, pleural sac and peritoneum
Give three examples of where simple squamous epithelium is found?
Lining blood vessels (endothelium)
Lining closed cavities (mesothelium)
Pulmonary alveoli
Bowman’s capsule/loop of Henle
Give two functions of simple squamous epithelium?
Lubrication
Gas exchange
What appearance do simple cuboidal epithelial cells take?
A single layer of uniform cuboidal cells
Give 3 locations of simple cuboidal epithelia in the body?
Lining pancreatic ducts
Lining thyroid gland follicles
Lining the collecting ducts of the kidney
Lining the surface of the ovary
Give 2 functions of simple cuboidal epithelial cells?
Absorption
Hormone synthesis/storage
What appearance do simple columnar epithelia take?
Taller than they are wide, column shaped - single layer
Where is simple columnar epithelium found?
In virtually all the GI tract (from the oesophagus onwards)
-stomach -small intestine -colon
Lining the fallopian tube
What are the functions of simple columnar epithelium?
Absorption
Secretion
Lubrication
What appearance does pseudostratified epithelium take?
Every cell attached to basement membrane but nuclei lie at different heights and some cells don’t reach the lumen
Where can pseudostratified epithelium be found in the body?
Lining the nasal cavity
Lining the trachea
Lining the bronchi
Give functions of pseudostratified epithelium.
Absorption
Secretion of mucus
Particle trapping and removing
In which sorts of locations is (non keratinised) stratified squamous epithelium found? Give specific examples
Moist areas, subject to abrasion
Lining the vagina
Lining the oesophagus
Lining the oral cavity
Surface of the cornea
Where is keratinised stratified squamous epithelium found?
Epidermis - lining of skin
What is the main cell of the epidermis? What do they secrete?
Keratinocytes
Keratin
What do keratinocytes differentiate into at the outermost layers of the epidermis?
Corneocytes, become highly keratinised and lose nucleus
What are the 4 layers of the skin, from the outside inwards?
Horny Layer (Stratum Corneum)
Granular Layer
Prickle cell layer
Basal layer
In which layer of the skin are keratinocytes produced? By which process are they produced? What happens to these cells once they are produced?
Basal layer
By mitosis
Pass up through the layers
In which layer of the epidermis do keratinocytes start differentiating into corneocytes? What happens to them?
Granular layer
Lose their plasma membrane, nucleus - become highly keratinised
What are the ‘granules’ of the granular layer of the epidermis?
Keratohyalin granules
What is contained within keratohyalin granules?
Keratin Enzymes to break down the phospholipid bilayer Fibrous proteins (e.g. Fillagrin and involucrin)
What are the functions of fillagrin and involucrin respectively?
Fillagrin - aggregates keratins
Involucrin - helps forms corneocyte envelope
What cells does the horny layer (stratum corneum) consist of?
Layers of flattened corneocytes
What is the rough transit time of a keratinocyte from the basal layer to the horny layer?
28-40 days
Name two cells of the epidermis (excluding keratinocytes and corneocytes)
Melanocytes
Langerhans cells
What is the function of melanocytes? At which layer of the epidermis do they exist?
Produce melanin
Basal layer
A dark skinned individual has more melanin, do they have more melanocytes?
No they have the same number
In which layer of the epidermis do Langerhans cells exist?
The prickle cell layer
What appearance does transitional epithelium take? Where is it exclusively found?
Surface cells vary in shape from columnar to cuboidal to flattened
Found only in urinary tract
Define gland
An epithelial cell or collection of cells specialised for secretion
Are exocrine and endocrine gland with or without ducts?
Exocrine = with ducts Endocrine = ductless
Give an example of a unicellular exocrine gland
Goblet cell
On which protein does Cystic fibrosis have its effect? What effect does this have in the respiratory tract?
CFTR - misfolded/not present in apical membrane of epithelial cells
Chloride ions cannot be pumped out of the cell, water can’t follow to hydrate secreted mucus —> mucus is too viscous —> pulmonary infection
What effect can cystic fibrosis have in the gut?
Can result in meconiumileus in new borns (cant pass 1st faeces)
In adults, constipation
Glands can be categorised into which 2 categories based on their physical appearance/structure?
Acinar (bunch of grapes —> 1 large duct)
Tubular (secretory cells line a tubule)
What are 3 methods of secretion at glands?
Merocrine
Apocrine
Holocrine
What is merocrine secretion?
Standard exocytosis - majority of glands
What is apocrine secretion? Give an example.
Secreted droplets are covered by plasmalemma
E.g. Breast milk
What is holocrine secretion? Give an example
Whole cell breaks down and becomes secretory product
Sebaceous glands of the skin
What test can be done to confirm a diagnosis of cystic fibrosis?
Salty sweat test
No CFTR - so chloride ions can’t be reabsorbed, often in high levels in sweat
What are the 3 major salivary glands? What do each of the glands largely secrete?
Parotid (enzymes)
Submandibular (mucus)
Sublingual (mucus)
What effects does cystic fibrosis have outside the respiratory tract and gut?
Infertility - no vas deferens
Blocking of ducts in the pancreas —> inflammation (pancreatitis)
