Session 5.2c - Lecture 1 - Epithelial Tissues and Glands Flashcards
Slides 37 - 49
What are basal bodies?
A protein structure (ultrastructure) found at the base of the cilia
What do you find at the base of the cilia?
Basal bodies
How do basal bodies appear on a histology slide?
They create a distinct line at the base of the cilia
What type of epithelium is pseudostratified epithelium (simple or complex)?
Simple
Fig. 37
Where is the basement membrane?
Light pink layer underneath the psuedostratified epithelia (opposite side to cilia) (?)
How fast does the cilia beta?
12 Hz (12 beats per second)
What is a Hz?
One cycle per second
What is the SI unit that denotes one cycle per second?
Hz
What is the function of the cilia?
To move that mucous blanket along
As well as the mucous blanket of the cilia, what else does it move?
Trapped dust particles
What are trapped dust particles in the respiratory tract moved by?
The mucous blanket on the cilia
What does the mucous blanket of the cilia move with it?
Trapped dust particles/microbes
What do we call the process of movement of trapped dust particles on mucous to the pharynx?
This mechanism is termed the ‘mucociliary escalator’)
What is the mucociliary escalator?
The cilia (1) beat at 12 Hz within a watery sol exuded (1) by the epithelium (1). Above this (1) is a viscoelastic (1) mucous blanket (1), secreted (1) by the goblet cells (1), which immobilises (1) particles (1) and lubricates (1) their passage to the pharynx (1), where they are swallowed (1).
Where does the mucous ultimately end up in our mucociliary escalator?
At the back of our pharynx
What happens to the mucous from the mucociliary escalator when it reaches our pharynx?
We largely subconsciously swallow the dust/particles/microbes etc. brought along with it.
Where do the cilia beat?
Within a watery sol exuded by the epithelium
Why does the epithelium of the respiratory tract need to exude a water sol?
So the cilia can beat
What lies above the cilia?
A viscoelastic mucous blanket
What secretes the viscoelastic mucous blanket in the mucociliary escalator?
Goblet cells
What is the function of the viscoelastic mucous blanket?
To immobilise particles and lubricate their passage to the pharynx.
What happens to the mucous once it reaches the pharynx?
They are swallowed.
What is the mechanism of mucous movement in from the cilia to the pharynx known as?
The mucociliary escalator.
What is the mucociliary escalator?
The movement of mucous (secreted by goblet cells) that lies above the ciliated epithelium (the cilia itself lie in a watery solute exuded by the epithelium), which brings along with it dust particles and microbes, that it traps and sends to the pharynx, where it is subconsciously swallowed. The cilia beat at about 12 Hz (12x per second).
Fig. 37
Caption and label this image.
G G - for goblet cells
Note the distinct line created by the basal bodies of the cilia.
Pseudostratified ciliated epithelium of the trachea.
Draw the epithelium of the trachea as it would appear on a histology slide.
See Fig. 37
G G - for goblet cells
Note the distinct line created by the basal bodies of the cilia.
Pseudostratified ciliated epithelium of the trachea.
What are the locations of psuedostratified epithelia?
- Lining of nasal cavity
- Trachea
- Bronchi
(So a whole big area of the upper respiratory tract)
- Ductus deferens (vas deferens - male reproductive system)
What epithelia is mostly found in the upper respiratory tract?
Pseudostratified epithelia
What epithelia is found in the lining of the nasal cavity?
Pseudostratified epithelia
What epithelia is found in the trachea?
Pseudostratified epithelia
What epithelia is found in the bronchi?
Pseudostratified epithelia
What are the functions of pseudostratified epithelia?
- Secretion and conduit
- Mucus secretion
- Particle trapping and removal
Where does pseudostratified epithelia perform the function of secretion and conduit?
- Respiratory tract
- Ductus deferens (vas deferens of male reproductive system)
What functions does pseudostratified epithelia perform in the respiratory tract and ductus deferens?
Secretion and conduit
Where does pseudostratified epithelia perform the function of mucus secretion?
Respiratory tract
Where does pseudostratified epithelia perform the function of particle trapping and removal?
Respiratory tract
What functions does pseudostratified epithelia perform specifically in the respiratory tract?
- Mucus secretion
- Particle trapping and removal
What is the ductus deferens?
The vas deferens, found in the male reproductive system
What is the role of the ductus deferens?
Transports sperm for ejaculation
Where does the ductus deferens transport sperm to and from?
The epididymis to the ejaculatory ducts
What is stratified epithelia?
Epithelia that is several layers thick. These cells can be of all different types.
Cells within stratified epithelia can be of all different types (e.g. squamous, cuboidal, columnar etc.). How do we classify this epithelia?
By the layer which is furthest away from the basement membrane/closest to the lumen
- so if the cells closest to the lumen are flat we call it stratified squamous, and so on (even if the other cells are cuboidal, columnar etc.).
What are the layers, from lumen to basement membrane, of stratified squamous epithelia?
Lumen
Layer of squamous cells
Layer of any type of cells (squamous, cuboidal, columnar etc.)
Basement membrane
Fig. 39
Caption and label this image.
Stratified squamous epithelia contain multiple layers of cells, the outermost (nearest the lumen/furthest from the basement membrane) of which are thin squamous cells.
Draw a diagram depicting stratified squamous epithelia.
See Fig. 39
Stratified squamous epithelia contain multiple layers of cells, the outermost (nearest the lumen/furthest from the basement membrane) of which are thin squamous cells.
- Cells more than one cell layer thick (i.e. not all cells touch the basement membrane (BM)) (1)
- Cells touching the BM/in the middle can be of any cell type (1)
- Cells nearest the lumen MUST be squamous (1)
- Basement membrane and lumen indicated (1)
What epithelia lines the vaginal wall?
Stratified squamous, non-keratinised epithelium
What are the vaginal epithelial cells rich in?
Glycogen
Collagen?
Why is it important that vaginal epithelial cells are rich in glycogen (collagen?)?
This is a substrate for lactobacilli
What is lactobacilli?
Lactobacillus is a genus of Gram-positive, facultative anaerobic, rod-shaped, non-spore-forming bacteria. They are a major part of the lactic acid bacteria group (i.e., they convert sugars to lactic acid). In humans, they constitute a significant component of the microbiota at a number of body sites, particularly part of the vaginal flora to regulate the pH, keeping it acidic to prevent infections.
How does the the vagina keep a low pH?
Glycogen is used as a substrate for lactobacilli, which converts this to lactic acid.
Why is the production of lactic acid important in the vagina?
To keep a low pH.
What pH does the vagina need to be kept at?
Low (acidic)
What is the significance of the vagina being kept at a low pH?
A low pH is healthy for the vaginal wall and stops colonisation by all sorts of other bacteria
Give 2 examples of how epithelia have functions other than a barrier or lining.
ANY 2 from:
- Vagina: stratified squamous non-keratinised epithelia produce lactic acid to keep the vagina a low pH
- Upper respiratory tract: pseudostratified epithelia produce mucous for the mucociliary tract
- Thyroid: simple cuboidal epithelia produce thyroxine
Accept other reasonable answers.
Explain the function of stratified squamous, non-keratinised epithelium of the vagina.
The cells are rich in glycogen, a substrate for lactobacilli, which produce lactic acid and thereby maintain a suitably low pH.
Fig. 40
Caption this image.
Stratified squamous, non-keratinised epithelium of the vagina
Draw an image depicting stratified squamous, non-keratinised epithelium of the vagina.
See Fig. 40
- Multiple layers
- Nearest the lumen they are squamous (flat)
- Other cells of any cell type
- Basement membrane underneath
What epithelia lines the oesophagus?
Stratified squamous, non-keratinised epithelium
Why is it important the oesophagus epithelia is statified?
These cells can come off as well – these can just slough off, if you swallow a particularly chunky bit of shredded wheat, these protect your oesophagus from abrasions: some of them can just slough off but there are plenty of cells underneath and there’s no bleeding
What is the function of the epithelia in the oesophagus?
To protect from abrasions and bleeding
Where is the blood supply found in epithelia?
ALL epithelia are avascular: they sit on their BM and they have no blood vessel
Give 2 examples of tissues that are avascular.
- Epithelial tissue
- Cartilage
(Also accept:
- cornea
- lens of the eye)
Where is the blood supply found in mucous/serous membranes?
There are blood vessels all over the place in the subtending CT but epithelia don’t have them
Epithelia don’t have a blood supply. How do they get their nutrients?
Sitting up there w/o a blood supply, and sort of going we don’t need your blood, we get our NUTRIENTS just by DIFFUSION, and our OXYGEN from the AIR
(like an independent Scot sitting above Hadrian’s Wall in Northern England)
Epithelia don’t have a blood supply. How do they get their oxygen?
Sitting up there w/o a blood supply, and sort of going we don’t need your blood, we get our NUTRIENTS just by DIFFUSION, and our OXYGEN from the AIR
(like an independent Scot sitting above Hadrian’s Wall in Northern England)
Where are stratified squamous non-keratinised epithelia found?
Stratified squamous non-keratinised epithelia are found in areas that are moist and subject to varying degrees of abrasion.
What is the function of the epithelia that lines the oesophagus?
Stratified squamous non-keratinised epithelia lines the wall of the oesophagus protecting it from abrasion.
Fig. 41
Label and caption the image.
- epithelium
- blood vessels
- lamina propria
- muscularis mucosae
Stratified squamous non-keratinised epithelia lines the wall of the oesophagus
Draw stratified squamous non-keratinised epithelia lining the wall of the oesophagus.
See Fig. 41
- epithelium
- blood vessels
- lamina propria
- muscularis mucosae
Stratified squamous non-keratinised epithelia lines the wall of the oesophagus
Fig. 41
Is this a mucous or serous membrane? Explain.
Mucous membrane:
- Not in the pericardium, pleural sac or peritoneum (in the oesophagus)
- Epithelia is stratified: serosa ONLY have simple squamous mesothelium
- Has a lamina propria
- Muscularis mucosae is present (mucosae i.e. mucous) - only found in alimentary tract, however
NOT a serous membrane (double layered) bc:
- Only found in pericardium, peritoneum and pleural sac
- Epithelium is ALWAYS simple squamous
- Do not have a lamina propria, just a thin layer of connective tissue
Where is stratified squamous non-keratinised epithelium located?
- Oral cavity
- Oesophagus
- Vagina
- Part of anal canal
- Surface of cornea
- Inner surface of eyelid
What epithelia lines the oral cavity?
Stratified squamous non-keratinised epithelia
How can we visualise the stratified squamous non-keratinised epithelia in your oral cavity?
In your GCSE class you may have scraped off with your finger some simple squamous cells and put them on a slide and looked at them under a microscope
What epithelia lines the oesophagus?
Stratified squamous non-keratinised epithelia
What epithelia lines the vagina?
Stratified squamous non-keratinised epithelia
What epithelia lines part of the anal canal to protect from abrasion?
Stratified squamous non-keratinised epithelia
What epithelia lines the surface of our cornea?
Stratified squamous non-keratinised epithelia
Where is our cornea?
In our eye