The Common Integument Flashcards
Lect 3 Week 1 Basu
What is the common integument?
the outer barrier of the organism
What does the common integument reflect?
the health of the animal
What is the common integument often affected by?
underlying diseases
What are the components of the common integument?
The subcutis and the cutis
What is the cutis made up of?
The dermis and the epidermis
What is the subcutis also known as?
Hypodermis or superficial fascia or subcutaneous tissue
What is the subcutis?
the piece of tissue that is beneath the skin
Give 5 examples of modified skin structures which fall under the common integument:
hair follicles + hairs
Skin glands, incl. mammary glands
foot pads
nails/claws/hooves
Horns + antlers
Describe what the subcutis is:
loose connective tissue between the skin and the muscle fascia
What component of the skin contains white fat?
the subcutis
What is white fat also known as in terms of tissue?
adipose tissue
Give three uses and benefits of adipose tissue:
Insulation, energy source, padding/protection (e.g. footpads)
The texture of the subcutis is dependent on what?
on water content
DRIER = STIFFER
What causes folds in the subcutis?
regional variations in fat and thickness of subcutaneous tissues
Why is the subcutaneous space important?
subcutaneous injection site
and is also a source of breed variation in dogs
What does the subcutis ‘sit on’, what is it attached to?
underlying cutaneous muslce
What is cutaneous muscle?
‘flat muscle sheets’
Thin, interrupted sheets spread over the body in the subcutis
What provides means for active movement of the skin?
muscle
Why is active movement of the skin useful?
e.g. horses use it as a diagnostic tool to shift flies
What is the cutaneous muscle called that is found over the neck and face?
platysma
What is the cutaneous muscle found over the frontal bone of the skull?
Frontalis
In which animal is the frontalis absent?
horses
What is the cutaneous trunci?
Covers the lateral sides of the trunk (torso) AND DORSALLY IN CATS to the tail
Describe the location of the cutaneous colli?
from sternum. spreads up neck
In what animal is the cutaneous colli best developed in?
horses
Name 6 cutaneous muscles:
platysma, frontalis, cutaneous trunci, cutaneous colli, cutaneous omobrachialis (continuation of trunci), preputial muscles
Describe the location of the cutaneous omobrachialis:
continuation of the cutaneous trunci over the shoulder and arm (ruminants and horses)
Describe the location of the preputial muscles:
connecting ventral midline to prepuce (carnivores, ruminants, pigs)
How is the dermis attached to the epidermis?
via interlocking papillae and ridges
What can adhesion (between the dermis and epidermis) be disrupted by?
repeated mechanical stress e.g. a blister
What is the dermis primarily composed of?
Connective tissue
What is the connective tissue composed of and what property does this give the skin?
composed of collagen (types I & II) and elastin = makes skin tough and stretchy
Describe quantity of cells the dermis has?
has few cells
What two regions does the dermis have?
a superficial papillary region & a deeper reticular region
What are papillae?
finger like projections, like interlaced fingers locking them together JOINING the dermis and the epidermis
Why are the papillae and ridges interlocking?
If they were flat then the dermis and epidermis would rub together easily and be easier to peel off
What is the superficial papillary region?
where the actual ‘finger-like’ projections are, the papillae
What is the deeper reticular region?
deeper, under the papillary dermis
How are the collagen fibres orientated?
in a particular way known as tension lines or Langer’s lines
Why are tension lines important to be aware of?
when making an incision, you do not want to make an incision across the lines of tension, you would want to make it ALONG the lines of tension
Explain why you wouldn’t want to make an incision across the lines of tension?
much harder to bring wound back together as the lines of tension would pull the wound apart
Name 7 components of the dermis:
blood vessels, lymphatic vessels, nerves, sensory receptors e.g. Pacinian corpuscule, hair follicles, arrector pili muscles, sebaceous + sweat glands
Which layer is the most superficial layer of the skin?
the epidermis
describe the quantity of the cells in the epidermis:
rich in cells
what does the epidermis lack?
nerves and blood vessels
what kind of epithelium is the epidermis?
stratified squamous epithelium
How many layers make up the epidermis?
4 or 5 layers
How do we name a stratified epithelium?
Named after the most superficial layer/most visible layer
Give the meaning behind the name stratum basale:
right next to the basement membrane
What are the 5 layers of a stratified squamous epithelium?
Stratum basale (near BM)
Stratum spinosum
Stratum granulosum
Stratum lucidum
Stratum corneum (most superficial)
What are keratinocytes?
skin cells
Where are keratinocytes produced?
stratum basale - by mitotic cell division
what is the duration of the complete cycle of keratinocytes?
20-30 days
Briefly describe the complete cycle of the keratinocytes:
they move to the surface of the skin (produced in stratum basale, near BM remember)
Differentiating (changing) as they go before eventually sloughing off (falling off)
What does the duration of the complete cycle of cell moving from stratum basale to skin surface depend on?
external circumstances: temperature
internal circumstances: age, hormonal status
Describe what happens in the stratum basale and where it is found?
Attachment to the dermis, most closely spatially related to the dermis (basement membrane)
and it is the site where mitosis of keratinocytes occurs
What happens in the stratum granulosum?
The keratinocytes are synthesising the protein/keratin granules which are needed for keratinisation.
what is keratinisation?
the process of turning keratinocytes INTO corneocytes
Tell me about the stratum lucidum:
very thin layer, sometimes it is there and other times it isn’t
Describe the stratum corneum:
thick (depends on where you are in the body) waterproof cell membrane
dead cells (no organelles or nuclei)
fewer cell-cell attachments so can slough off
all of their proteins inside have been replaced by keratin which essentially suffocates and kills the cell
Describe the varying thickness of the layers, especially the stratum corneum:
different layers can be different thicknesses in different parts of the body e.g. S.corneum is thicker at footpad
and it is especially the stratum corneum because this layer has direct contact with the external environment
What are melanocytes and where are they found?
they are pigment cells and are found in the stratum basale and they protect against sun radiation
What 4 cells are found in the epidermis?
keratinocytes, corneocytes, melanocytes, langerhans (immune) cells
What do melanocytes produce?
melanin pigment
What do melanocytes do with the melanin pigment?
distribute it to other cells - pass to keratinocytes via cellular processes
What is the basement membrane (BM) sometimes called?
The basal lamina
why don’t the melanocytes cells found in the most superficial layer of the epidermis take up stain very well?
because the nuclei have died, fewer proteins so don’t take up dye
What are Langerhans cells also known as?
epidermal macrophages
What are Langerhans cells?
antigen-presenting cells with cytoplasmic processes
What other cells - apart from melanocytes also appear as poorly histologically stained cells?
Langerhans cells
What do epithelia cells rely on for nutrients?
diffusion
the epidermis has no…
BLOOD VESSLES (no blood supply)
The dermis is very well…
vascularised
meaning of vascularised?
lots of blood vessels
how are the blood vessels in the dermis arranged?
into three plexuses
what is a plexus?
a network - a mesh type of arrangement of blood vessels
Describe the blood supply to the skin in three different points:
- Cutaneous arteries (and veins) leave the subcutaneous plexus and pierce into the dermis
- Form a deep network of vessels: reticular vascular plexus
- Arterioles and venules reach the papillary dermis: Superficial papillary plexus
What are the three plexuses that the dermis is contains?
Subcutaneous plexus
Reticular vascular plexus
Superficial papillary plexus
Which plexus do the capillaries branch off of?
Off of the superficial papillary plexus
How can we control the blood supply to the skin?
The walls of the arteries can dilate or constrict in order to increase/reduce blood supply
What does this mean ‘Dermis and the subcutis are well-innervated’
That the dermis and the subcutis have a good supply of nerves
What two types of nerves do the dermis and subcutis have?
Sensory and autonomic
What do the autonomic nerves do?
regulate bodily functions e.g. temperature
What 3 things do the autonomic nerves within the dermis supply?
sweat glands, arrector pili muscles, blood vessels
Sensory nerves can terminate in free nerve endings, what three different types are they?
pressure, heat and pain
Other sensory nerves terminate in what else? (STATE 2)
Corpuscles or hair follicle receptors
What are corpuscles?
encapsulated nerve endings
Which type of sensory neurone are very sensitive pressure sensors?
the sensory nerves that terminate in corpuscles or hair follicle receptors
How do adipocytes appear under a microscope?
they appear as vacant cells with the nucleus pushed to the side - the nucleus is found at the periphery
What layer of the integument is the ‘quick’?
the dermis
Name the 11 components of the foot of the horse:
The toe
Quarter
Heel
Bar
Apex of the frog
Central sulcus
Lateral/medial sulcus
Bulb
Sole
White line
Hoof wall
