Integument 1 Flashcards
What is the common integument?
- the outer barrier of the organism
The common integument is not just skin what else does it include?
- subcutis (AKA hypodermis/superficial fascia)
- skin = dermis and epidermis
- hair follicles and hairs
- skin glands and marry glands
- foot pads
- hooves, nails, claws
- horns and antlers
What is the subcutis?
- loose connective tissue between skin and the muscle fascia
What does the subcutis contain?
- white fat (adipose tissue)
What does adipose tissue in the subcutis provide?
- insulation
- energy source
- padding/protection (e.g., footpads)
There are regional variations in fat and thickness - describe these:
- fat accumulation such as nuchal region of horse
- local thickenings allow folds
- provide areas for subcuticular injections
What muscles are in the subcutis?
- cutaneous muscles
What are cutaneous muscles?
- thin, interrupted muscle sheets spread over the body in the subcutis allow for skin movement
Name the cutaneous muscles:
- platysma
- frontalis
- cutaneous colli
- cutaneous trunci
- cutaneous omobrachialis
- preputial
Where is the platysma located?
- over the neck and face
Where is the frontalis located and what animal does not have this?
- over the frontal bone (absent in horses)
Where is the cutaneous colli located and what animal is this muscle best developed in?
- from the sternum and spreads up neck (best developed in horses)
Where is the cutaneous trunci located?
- covers the side of the trunk - not in humans
Where is the cutaneous omobrachialis located and what animals is it found in?
- continuous of the cutaneous trunci over the shoulder and arm (ruminants and horses)
Where us the preputial muscles located and what animals it is found in?
- muscles connecting ventral midline to prepuce (carnivores, ruminants and pigs)
What is the cutis (skin) composed of?
- composed if dermis and epidermis
What does the dermis determine?
- the dermis determines the thickness of the skin
- there are regional variations
The dermis is the deep layer - what is it made up of?
- fibrous connective tissues
= few cells, not may nuclei
= collagen fibres (types 1, 3, 5)
= elastin fibres
The collagen fibres un the dermis are orientated un particular ways what are these known as?
- tension or langers lines
Why are langer lines useful?
- they make closing incisions easier
The dermis contains different regions what are these regions called?
- a superficial papillary region
- a deeper reticular region
What can regions in the epidermis do?
- can project up into epidermis
- some regions have ridge-like projections (increase surface area/ contact between dermis and epidermis)
- papilla region anchors down
What components does the cutis - dermis also contain?
- blood vessels (vasodilation and constriction)
- lymphatic vessels
- nerves
- sensory receptors e.g., pacinian corpuscle
- hair follicles
- arrector pili muscles (sympathetic innervation)
- sebaceous and sweat glands (thermoregulation)
The epidermis within the cutis contains 4-5 layers what are these called?
- stratum basale (deepest)
- stratum spinosum
- stratum granulosum
- (stratum lucidum)
- stratum corneum (closes to top)
= can long giraffe spines bend
What are skin cells called?
- keratinocytes
Where are keratinocytes produced?
- produced in the stratum basale by miotic cell division
How does skin replace itself?
- keratinocytes move to the skin surface, differentiating as they go, before eventually sloughing off
- complete cycle 20-30 days depending on species
Describe the stratum basale:
- attachment to basement membrane
- proliferation (stem cells) = new cells being produced to replace skin cells
Describe the stratum spinosum:
- cells closely adhered by desmosomes
- desmosome junctions make cells look spiny under microscope
Describe the stratum granulosum?
- keratinocytes here contain densely staining kertohyalin granules
- kertohylain granules contain products needed for keratinisation
What is keratinisation?
- process of turning keratinocytes to corneocytes
= flattened tough cell on outside of dermis for protection
Describe the lucidum:
- clear layer
- found only in thick, non-hairy skin such as the footpad
Describe the stratum corneum:
- thick waterproof cell membrane
- look dead (non organelles or nuclei)
- fewer desmosome attachments so cells can slough off
The thickness of the epidermal layers varies in thickness in different parts of the body.
Where is the spinosum thickest?
And what is the thin skin?
- the spinosum is very thick at footpad
- granulosum = hard to see in thin skin
What cells does the epidermis contain?
- mostly kertinocytes/corneocytes
- melanocytes (pigment cells to protect against the suns radiation)
- Langerhans/dendritic cells = immune cells
- Merkel’s cells (touch receptors)
Where are melanocytes and what do they do?
- sit in deep layer and pass pigment packets around them
- cells look clear in stratum basale and help to protect from irradiation damage
What germ layer does the epidermis (hair follicles, nails, and glands) come from?
- ectoderm origin
What germ layer does the dermis and subcutis come from?
- mesoderm origin
What germ layer do melanocytes come from?
- derive from the neural crest cells
- also found in eyes and ears
At a later embryonic stage what does the mesoderm organise itself into?
- blocks of tissue (somites)
What is the dermatome?
- segment of dermis derived from one somite, and thus innervated by a single spinal nerve (per body half)
- can vary between individual
- some overlap in innervation
How can innervation of the skin be represented?
- it can be mapped
After exiting the vertebra, the spinal nerve does what?
- splits into dorsal and ventral branches
What does the dorsal branches generally supply?
- supply the dorsal cutaneous nerves innervating the dorsal body skin
What does the ventral branches generally supply?
- supply the ventral and lateral cutaneous nerves innervating the ventral and lateral body skin
What can the dorsal and ventral branches aid in?
- helps to localise nerve issues
The limb skin is also supplied by spinal nerves - what do these form within the limb?
- form the brachial and lumbar plexuses
Nerve regions can overlap in the skin what does this lead to?
- multiple nerves receiving skin sensations
What are non-overlapping regions?
- areas supplied by a single nerve = autonomous zones
What are autonomous zones critical for:
- diagnosis and prognosis of peripheral nerve lesions
- successful local anaesthesia
Cutaneous innervation can be split into sensory information and sympathetic motor innervation -
What is involved in sensory information?
- free nerve endings (pain, itch)
- Merkel cells (touch, pressure)
- Pacinian corpuscles (deep pressure)
= afferent
Sympathetic motor innervation innervates what?
- blood vessels
- sweat glands
- pilomotor apparatus
How does the common integument provide protection?
- physical (fat, collagen, keratin)
- radiation (melanocytes)
- epidermal organs (horns and claws)
How does the common integument provide immune defence?
- physical barrier to infection
- immune cells in skin
- antimicrobial properties of skin gland secretions
How is the common integument involved in sensing the environment?
- pressure receptors
-pain receptors - heat receptors
- cold receptors
- tactile hairs
- toruli tactile
How is the common integument involved in thermoregulation?
- sweating
- hairs, piloerection and arrector pilli
- blood flow to skin
- insulation by fat
How is the common integument involved in storage excretion?
- fat stores energy, water and vitamins
- glands can excrete water and electrocytes
How is the common integument involved in communication/camouflage?
- smelly substances from glands (olfactory)
- epidermal organs (horns) = status symbol
- raising of hair or feathers (arrector pili) = aggression
- pigmentation (melanocytes) = camouflage
How is the common integument involved in selective permeability?
- impermeable to water (waterproof epidermis, oily secretions from glands) maintain water and electrolyte balance
- some medications can be absorbed across the skin
- some species use skin for respiration
What can burns lead to?
- can lead to loss of water from skin and dehydration
