1 - common integument Flashcards
What is the definition of the common integument?
The outer barrier of the organism, not just skin
What does the common integument include?
Subcutaneous tissue
Dermis and Epidermis (skin)
Modified skin structures
Give some examples of modified skin structures
Hair follciles Hair Skin glands, including mammary glands Foot pads Nails/claws/hooves Horns and Antlers
What is the general relevance of the common integument (why is it useful to look at)?
It reflects the underlying health of the animal and is affected often by underlying disease.
What is the subcutaneous tissue?
Loose connective tissue between the skin and muscle fascia.
What does the subcutaneous tissue contain and what is the purpose of these things?
White fat (adipose tissue) - for insulation, as an energy source and for padding and protection. Tiny tendons from underlying muscles for skin movement (skin twitching)
What is the relevance of regional variations in fat and thickness of subcutaneous tissue?
- Causes skin folds that are characteristic of some breeds
- Is important when considering subcutaneous injection sites
What is the skin composed of?
Dermis and epidermis
What is another name for the subcutaneous tissue?
Subcutis
What are other names for the skin?
Cutis and hypodermis
What determines thickness of the skin?
Why
dermis
Because theres regional variations in its thickness
What is the dermis made up of?
Fibrous connective tissue which includes collagen fibres and elastin fibres
What Type of collagen fibres are in the dermis?
Type 1, 3 and 5
Why must the collagen fibres in the dermis be considered?
They are oriented in ways in the dermis called langers lines/tension lines. Tension runs along these lines pulling wounds apart.
Important to consider in surgery planning/wound healing.
What happens to wounds perpendicular to langers lines?
They open
What happens to wounds parallel to langers lines?
They close
Aside from connective tissue what else does the dermis contain?
Blood vessels Lymphatic vessels Nerves Sensory receptors Hair follicles Arrector pili muscles Sebaceous and sweat glands
What do arrector pili muscles do?
Attach to base of hair follcile and flatten and raise the hairs.
Name the layers of the epidermis from bottom to top (give both names)
- Stratum basale/basal layer
- Stratum spinosum/spiny layer
- Stratum granulosum/granular layer
- Stratum lucidum/ clear layer
- Stratum corneum/ corneal layer
What are skin cells called?
Keratinocytes
Where are keratinocytes produced and by what type of cell division?
Stratum basale by mitotic cell division.
What journey to keratinocytes make after they have been produced (what happens to them).
And how long does this process take?
They move up through the epidermal layers to the skins surface and differentiate as they go, then eventually slough off.
Takes 20-30 days depending on species.
Where is the stratum basale?
Attached to the dermis
What happens in the stratum basale?
Proliferation of cells by mitosis
Describe the cells in the stratum spinosum.
The cells are closely adhered by desmosomes, these desmosome junctions make cells look spiny under the microscope.
Why do cells in the spinosum look spiny?
When processed the cells shrink so all that remains is the desmosome attachments.
Describe the cells in the stratum granulosum.
The keratinocytes here contain densely staining keratohyalin granules.
These granules contain products needed for keratinisation.
What is keratinisation?
The process of turning keratinocytes into corneocytes.
Describe the stratum lucidum and say where it is found.
Clear layer.
Its found only in thick non hairy skin like the footpad.
Its the young cells of the stratum corneum and its not always very evident
Describe the cells of the stratum corneum
They have a thick
waterproof cell membrane
They look dead because they’ve no organelles or nuclei - but are a little metabolically active
They have fewer desmosome attachments so cells can slough off.
Give an example of where the spinosum is very thick?
Footpad
What 4 cell types make up the skin
And which are most abundant
They are mostly keratinocytes/corneocytes.
But theres also melanocytes, langerhans cells and merkels cells
Where in the skin are melanocytes and what do they do?
In the basal layer.
They produce the pigment melanin which protect cells against sun radiation.
Name the 7 functions of the integument.
- Protection
- Immune defence
- Sensing the environment
- Thermoregulation
- storage and excretion
- Communication and camouflage
- Selective permeability
How does the integument give protection to animals (hint 3 ways)
Physical protection - e.g. fat, collagen and keratin
Protection from radiation - e.g. the melanocytes
Epidermal organs e.g. horns and claws
How is the integument involved with immune defence?
It is a physical barrier to infection
There are immune cells in the skin
Some skin gland secretions have antimicrobial properties
How is the integument involved in sensing the environment?
It has:
- Pressure receptors
- Pain receptors
- Heat and Cold receptors
- Tactile hairs
- Toruli tactiles
What are toruli tactiles and what do they do?
They are raised elevations on the rkin like little bumps which help the animal sense whats around it.
How does the integument help with thermoregulation?
Through:
- Sweating
- The hairs, piloerection and arrector pili (can make hairs stand up or lie flat)
- Blood flow to the skin
- There is fat which insulates
How does the integument function in storage and excretion?
Fat in the skin stores energy, water and vitamins
Glands in the skin can excrete water and electrolytes.
How does the integument function in communication and camouflage?
Animals can secrete smelly substances from glands like pheromones that are used to communicate
The integument includes epidermal organs like horns which are used in threat displays
Animals can raise feathers or hairs via arrector pili muscles which can be used in displays
Skin pigmentation via melanocytes mean that the skin is coloured which can convey a message.
How is the integument involved in selective permeability?
Most animals skin is impermeable to water (because the epidermis is waterproof and oily secretions from glands help waterproof) this maintains water balance.
But some medications can be absorbed across the skin.
And some species use the skin for respiration (they have permeability across the skin)
What are the 3 germ layers?
Where are these layers in relation to each other (when flat)?
Ectoderm - top
Mesoderm - middle
Endoderm - bottom
What group of tissues does the ectoderm form?
Epidermal and neural cells
These form things like skin , brain and hair, nails, claws…
What group of tissues does the mesoderm form?
Musculoskeletal system, connective tissues, organs and blood
What group of tissues does the endoderm form?
Lining of the gut and respiratory system, and outpouchings of the gut like liver and pancreas
Which germ layer does the epidermis develop from?
Ectoderm
Which germ layer do the dermis and subcutis develop from?
Mesoderm
Which germ layer do melanocytes develop from?
Ectoderm (neural crest cells)
Which germ layer do somites form from?
Mesoderm
What are dermatomes?
A section of dermis which is derived from one somite so is therefore innervated by a spingle spinal nerve
