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
What epithelia lines the inner surface of the eyelid?
Stratified squamous non-keratinised epithelia
What are the functions of stratified squamous non-keratinised epithelia?
- Protection against abrasion (all sites)
- Reduces water loss but remains moist (all sites)
How can we remember where we find stratified squamous non-keratinised epithelia?
Anywhere really that is prone to abrasion but is a moist surface is likely to have stratified squamous non-keratinised epithelium next to it or lining it.
What is the difference between SSNKE and stratified squamous keratinised epithelia (SSKE)?
SSKE contains multiple layers of cells, but the outermost ones are dead.
What does cornified mean?
Conversion of epithelium to the stratified squamous type. These cells are dead and have lost their nucleus.
What do we call cells that have been converted to dead, stratified squamous epithelia?
Cornified
What are the cornified cells of SSKE made out of?
They’re pure kertain, virtually
What is the outermost layer of cells on our epidemis made up of?
Cornified stratified squamous keratinised epithelium - this is what we can see and touch.
What are the outermost dead cells of the skin epithelium called?
The stratum corneum
What is the stratum corneum?
The outermost dead cells of the epithelium are collectively called the stratum corneum.
Describe the appearance of the stratum corneum
- squamous
- no nuclei
- highly keratinised
Where are squames of keratin found?
On the outermost layer of skin
What is a squame? (i.e. squame of keratin)
A scale or flake (as of skin)
What is the function of the stratum corneum?
- greatly reduces water loss and ingress (entry);
- prevents ingress of toxins;
- protects against abrasion;
- reduces microbial colonisation
How does the skin reduce water loss?
Due to the stratum corneum, which greatly reduces water loss and ingress
What is the role of stratum corneum and water?
- greatly reduces water loss and ingress (entry);
What is the role of stratum corneum and toxins?
- prevents ingress of toxins
What is the role of stratum corneum and abrasion?
- protects against abrasion
What is the role of stratum corneum and microbes?
- reduces microbial colonisation
Does our skin have microbes?
We’ve got loads of microbes on our skin, which is actually slightly acid, but we’d have many more, they’d be having a bonanza of a time if our skin was moist and wet and didn’t have stratum corneum on it
What is the pH of our skin?
Slightly acidic
Why is the pH of our skin slightly acidic?
Due to the presence of microbes
Why do we need the stratum corneum to protect us from microbes if we already have microbes on the skin?
we’ve got loads of microbes on our skin, which is actually slightly acid, but we’d have many more, they’d be having a bonanza of a time if our skin was moist and wet and didn’t have stratum corneum on it
Describe SSKE.
Stratified squamous keratinised epithelium contains multiple layers of cells, the outermost of which are squamous cells that have lost their nuclei and cornified (i.e. become ‘squames’ of keratin).
Fig. 43
Caption and label this image.
Keratinised stratified squamous epithelium
Stratified squamous keratinised epithelium contains multiple layers of cells, the outermost of which are squamous cells that have lost their nuclei and cornified (i.e. become ‘squames’ of keratin).
Draw an image of stratified squamous keratinised epithelium.
See Fig. 43
Stratified squamous keratinised epithelium contains multiple layers of cells, the outermost of which are squamous cells that have lost their nuclei and cornified (i.e. become ‘squames’ of keratin).
What does the epidermis of the skin contain?
- Stratum corneum (outermost dead layer)
- Living epithelial cells
- Basement membrane
Which part of the epidermis is dead?
The stratum corneum
Which part of the epidermis is alive?
The living epithelial cells, that is not the stratum corneum.
What lies underneath the epidermis?
The dermis
What is the dermis?
Connective tissue
Where in the skin do we find stratified squamous keratinised epithelium?
The epidermis of the skin is the primary site of stratified squamous keratinised epithelium.
Fig. 44
Label this image.
- Stratum corneum (dead squames of keratin)
- Epidermis
- Basement membrane
- Dermis
The epidermis of the skin is the primary site of stratified squamous keratinised epithelium.
Draw the skin as seen on a histology slide, up to the layer of the dermis.
See Fig. 44
- Stratum corneum (dead squames of keratin)
- Epidermis
- Basement membrane
- Dermis
The epidermis of the skin is the primary site of stratified squamous keratinised epithelium.
What separates the epidermis and the dermis?
The basement membrane
Where does the basement membrane lie in the skin?
Between the epidermis and dermis
What happens to the stratum corneum?
It is sloughed off all the time
What is 90% of house dust?
Stratum corneum
How much % does stratum corneum make up of house dust?
90%
Stratum corneum makes up 90% of what?
House dust
What do we lose all the time in our body, that can fall onto the floor?
Stratum corneum (outermost dead layer of skin)
What are house dust mites main source of food?
Stratum corneum (outermost dead layer of skin)
How can the stratum corneum be linked to allergies?
- Stratum corneum is outermost dead layer of skin
- This is constantly being shed
- The main source of food for house dust mites is dead skin cells that have shed (stratum corneum)
- House dust mites are one of the biggest causes of allergy
- Thus, the stratum corneum can propagate the reproduction of house dust mites, thus causing allergy
(This can be managed by regular cleaning, vacuuming, and specific dust-proof equipment etc.)
What do house dust mites eat?
House dust mites love shedded stratum corneum bc it’s their main source of food – they eat the fungi and bacteria that grow on it, as well as the squames themselves
Why do house dust mites eat stratum corneum?
They eat the fungi and bacteria that grow on it, as well as the squames themselves
The stratum corneum all the way down to the basement membrane is known as what layer?
Epidermis
What type of connective tissue is the dermis?
Dense irregular connective tissue
Where is dense irregular connective tissue predominantly found?
In the dermis of the skin
What structural components make up the dermis?
Type I collagen and elastin
What is the function of type I collagen in the dermis?
These are arranged in a dense irregular fashion, so you can move your skin quite roughly in every direction and it doesn’t damage.
Which fibre in the dermis is responsible for movement of the skin without damage?
Type I collagen
What is the function of elastin in the dermis?
Elasticity of the skin
Which fibre in the dermis is responsible for elasticity of the skin?
Elastin
Fig. 45
Label the image
- Stratum corneum
- Epidermis (like all epithelia epidermis contains no blood vessels - it is avascular)
- Dermis (dense irregular connective tissue consisting of collagen and elastin bundles orientated in all directions; leather is made out of dermis (collagen are the pink bundles, elastin cannot be seen on this stain)
Fig. 45
What are the pink bundles running in different directions?
Each one of these pink things is bundle of collagen I lying in every conceivable direction, which is why you can move your skin quite roughly in every direction and it doesn’t damage
Fig. 45
Where is the elastin on this stain?
Not shown on this stain
What is leather made out of?
Dermis - bc of the strong collagen bundles that can are in a dense irregular fashion, so can be made to withstand pressures and mechanical forces in many different directions
Draw a diagram showing the epidermis and dermis of the skin as it would appear on a histology slide.
See Fig. 45
- Stratum corneum (dead cells)
- Epidermis (like all epithelia epidermis contains no blood vessels - it is avascular) (living cells and BM)
- Dermis (dense irregular connective tissue consisting of collagen and elastin bundles orientated in all directions; leather is made out of dermis (collagen bundles)
Fig. 46
Caption this image.
- Artists’ diagram of the skin
- Epidermis pulled back in corner, showing interdigitation of epidermis and dermis
- Sweat gland lying down
What are dermal papillae?
The interdigitation between the epidermis and dermis layers of the skin
What interdigitates the epidermis and dermis together?
Dermal papillae
Why do the epidermis and dermis interdigitate?
Probs bc we don’t want blisters, you don’t want your epidermis slipping off the subtending CT and if everything was smooth it would move like this like sheets of paper, but if I put took 2 egg boxes and put them inside each other they wouldn’t move like that: and that’s the same reason for these dermal papillae – interdigitiation of epidermis and dermis
(To prevent blisters from movement)
What muscle is associated with hair follicles in the skin?
Arrector pili muscle
What is the arrector pili muscle associated with?
Hair follicles
What is the function of the arrector pili muscle?
Contraction of these muscles causes the hairs to stand on end, known colloquially as goose bumps.
What is a sebaceous (oil) gland?
A small gland in the skin which secretes a lubricating oily matter (sebum) into the hair follicles to lubricate the skin and hair.
What puts oily secretions onto hair?
Sebaceous glands
What are hair follicles associated with?
Arrector pili muscles (causes it to stand up on end) and sebaceous glands (secretes oil)
Where do sweat glands lie?
Deep in the dermis
What is the structure of a sweat gland?
A sweat gland is just a tube that dives down and then is highly curled – it’s a blind-ended (closed at one end) tube at its end and it produces sweat
What does blind-ended mean?
Closed at one end
Give an example of a blind-ended tube
- Eccrine sweat glands
- Lymphatic vessels
What produces sweat?
Apocrine or eccrine sweat glands
What is an eccrine gland?
Open by a duct directly onto the skin surface
Give an example of an eccrine gland.
Sweat gland
Where do we find blood vessels specifically in the dermis?
Deep plexus of slightly thicker little arterioles and venules connected by connecting vessels and then a finer plexus, just under the epidermis
What does the deep plexus of blood vessels in the dermis contain?
Slight thicker little arterioles and venules
What are the arterioles and venules in the deep plexus of the dermis connected by?
Connecting vessels
Where is the finer plexus of blood vessels in the dermis, specifically?
Just under the epidermis
Fig. 46
Label the image
- Hair shaft
- Dermal papillae
- Free nerve ending
- Sebaceous (oil) gland
- Sensory nerve fiber
- Arrector pili muscle
- Hair follicle
- Hair root
- Artery
- Vein
- Pacinian corpuscle
- Root hair plexus
- Adipose tissue
- Eccrine sweat gland
- Hypodermis (superficial fascia)
- Dermis
- -Papillary layer
- Reticular layer
- Epidermis
- Stratum corneum
- Stratum lucidum
- Stratum granulosum
- Stratum spinosum
- Stratum basale
- Pore
- Meissner’s corpuscle
Draw a cross-section of skin including all its components, e.g. hair follicle.
See Fig. 46
- Hair shaft
- Dermal papillae
- Free nerve ending
- Sebaceous (oil) gland
- Sensory nerve fiber
- Arrector pili muscle
- Hair follicle
- Hair root
- Artery
- Vein
- Pacinian corpuscle
- Root hair plexus
- Adipose tissue
- Eccrine sweat gland
- Hypodermis (superficial fascia)
- Dermis
- -Papillary layer
- Reticular layer
- Epidermis
- Stratum corneum
- Stratum lucidum
- Stratum granulosum
- Stratum spinosum
- Stratum basale
- Pore
- Meissner’s corpuscle
Fig. 46
Explain what each of these components do.
See page 292-295 for more details on the skin
How many sweat glands do we have?
Millions on our body surface
What happens to the blood vessels just under our epidermis when we get cold?
Our body can avoid losing heat by clamping down on these and stopping the blood flowing
Why do we look pale in cold weather?
The blood vessels in our epidermis clamp down, to prevent us from losing heat. Thus, the blood vessels constricting rids the skin of its colour, so we look pale.
Why do patients who have had a shock look pale?
Shock is the state of not enough blood flow to the tissues of the body as a result of problems with the circulatory system. The blood vessels in our epidermis therefore clamp down (vasoconstrict) to redirect blood flow to the major organs (heart, lungs, brain). Thus, the blood vessels constricting rids the skin of its colour, so we look pale.
Why do we look pink when we get too hot?
Our blood vessels open up (vasodilate) and the blood flows much more regularly.
Explain why we can get symptoms of looking pink or looking pale.
In diseases where pathophysiology results in vasoconstriction, we look pale bc blood flow is diverted away from the skin. Conversely, where pathophysiology results in vasodilation, we look pink bc blood flows much more regularly.
Give an example of a condition where we look pale, and explain the pathophysiology behind it.
Shock
- blood flow is directed away from the skin, thus the blood vessels vasoconstrict
- this rids the skin of its colour, so we look pale.
What is the pilosebaceous unit?
The pilosebaceous unit is the hair follicle, with its associated sebaceous gland and arrector pili muscle.
The hair follicle, sebaceous gland and arrector pili are associated together and have a name. What is it?
Pilosebaceous unit.
What is an apocrine sweat gland?
A sweat gland which is an exocrine gland, whose mechanism of secretion is via membrane budding.
Where are apocrine sweat glands found?
Only in certain places,
e. g. - axilla
- areola and nipples of the breast
- ear canal
- eyelids
- wings of the nostril
- perianal region
- some parts of the external genitalia
What type of sweat gland is associated with the hair follicle?
Apocrine or eccrine sweat gland, depending on the location
Where are eccrine sweat glands found?
All over the body, you including palms of your hands and soles of your feet where there are no hair follicles, they’re independent of hair follicles, and they produce the normal sweat that you make.
What are the differences between apocrine and eccrine sweat glands?
Apocrine:
- found only in certain regions, e.g. axilla, breast, ear canal etc.
- secretes sweat via the membrane budding
Eccrine:
- found all over the body, including areas where there is no associated hair (palms and soles of hands and feet, respectively)
- releases sweat via a duct directly onto skin
Fig. 47
Caption and label the image.
Pilosebaceous unit with apocrine and eccrine sweat glands
- Acrosyringium
- Eccrine duct
- Secretory coils of eccrine sweat gland
- Arrector pili muscle
- Sebaceous gland
- Hair follicle
- Apocrine sweat gland
What is the acrosyringium?
Eccrine glands are composed of an intraepidermal spiral duct, the “acrosyringium”; a dermal duct, consisting of a straight and coiled portion.
Draw a pilosebaceous unit with associated sweat glands.
See Fig. 47
Pilosebaceous unit with apocrine and eccrine sweat glands
- Acrosyringium (intraepidermal duct)
- Eccrine duct
- Secretory coils of eccrine sweat gland
- Arrector pili muscle (muscle attached to follicle)
- Sebaceous gland (Like a grape lump)
- Hair follicle
- Apocrine sweat gland (also has secretory coils. Both sweat glands are blind-ended)
Name 2 places where there is skin without any hair follicles.
- Sole of the foot
- Palm of your hand
What happens to the stratum corneum on the sole of your foot and palm of your hand?
It becomes much much thicker here
What happens to the cells of the stratum corneum?
Cells become granular and lose their nuclei (from the living epidermal cells) - that becomes really thick
Which cells of the epidermis become granular?
Stratum corneum
Fig. 48
Caption and label this image.
Epidermis of thick skin from the foot (stratified squamous keratinised epithelium).
- Dead keratinised epidermal cells
- Living epidermal cells
- Dermis (connective tissue)
Note the interdigitation between the dermis and the epidermis.
What epithelia is found on the thick skin of the foot?
SKIN - stratified squamous keratinised epithelium
Draw the epidermis of thick skin from the foot .
See Fig. 48
Epidermis of thick skin from the foot (stratified squamous keratinised epithelium).
- Dead keratinised epidermal cells
- Living epidermal cells
- Dermis (connective tissue)
Show interdigitation between the dermis and the epidermis.
Where is the granular layer of skin?
The layer of cells just underneath the stratum corneum
What occurs in the granular layer?
The squamous cells are becoming much more granular bc they’re filling up with keratin.
What is important about the basal layer?
It’s the one layer that divides/where mitosis takes place.
Which layer of the epidermis is dead?
Stratum corneum
Which layer of the epidermis do squamous cells fill up with keratin?
Granular layer (they become more granular bc they’re filling up with keratin)
Which layer of the epidermis undergoes mitosis?
Basal layer
In which direction do cells differentiate?
From deep to superficial - mitosis occurs in the basal layer and move up, all the while becoming terminally differentiated, and eventually die at the top layer (stratum corneum)
How long does one skin cell live for before it drops off (i.e. moves from the basal layer to stratum corneum)?
5 weeks
What takes 5 weeks in the skin?
For the cell to move up from the basal layer, up to the top before it drops off.
Fig. 49
Label and caption the image.
- stratum corneum
- granular layer
- prickle cell layer
- dermis
- basal layer
Normal epidermis from the side of finger.
Draw the normal epidermis from the side of finger, as would be seen on a histology slide.
See Fig. 49
- stratum corneum (dead squamous cells, no nuclei - mainly pink)
- granular layer (squamous cells becoming granular, pink and blue bc nuclei present)
- prickle cell layer (pink and blue bc nuclei present)
- dermis
- basal layer (lowest level of epidermis layer, even in interdigitation).
- Epidermis and dermis clearly defined from each other.
Normal epidermis from the side of finger.
