Integument 1; structure & function Flashcards
What are the 3 main layers of the common integument?
1) Epidermis
2) Dermis
3) Subcutis (hypodermis)
What other structures are included within the outer integument?
- Hair follicles
- Hairs
- Hooves
- Skin glands
- Mammary glands
- Footpads
- Horns
What is the subcutis?
A loose connective tissue between the skin and the muscle fascia
What are the thicker areas of the subcutis used for and why?
They are used for subcutaneous injections as they can cope with large volumes of fluid being injected.
What does the subcutis mainly contain?
What is this tissue used for?
Contains = adipose tissue (white fat)
Used for = Insulation, Energy source, Padding and protection
What are cutaneous muscles and where are they found?
- Thin, interrupted sheets of muscle
- Found in the subcutis
- Allow for skin movement
Where are each of these cutaneous muscles found?
1) Platysma
2) Frontalis
3) Cutaneous colli
4) Cutaneous trunchi
5) Cutaneous omobrachialis
6) Pre-putial muscles
1) Platysma = over face and neck
2) Frontalis = over frontal bone
3) Cutaneous colli = from sternum, spreads up the neck
4) Cutaneous trunci = covers side of the trunk
5) Cutaneous omobrachialis = Over the shoulder
6) Pre-putial muscles = Along the ventral midline
What is the cutis?
This is the skin, composed of dermis and epidermis.
Which layer of the cutis determines the thickness of the skin?
The dermis
Which muscle is responsible for making hairs on the skin stand up?
Arrector pili muscle
What type of nerve fibres innervate the arrector pilli muscles to make the hairs stand on end?
Sympathetic nerve fibres
What is the dermis?
- A fibrous connective tissue packed with collagen and elastic fibres
- Very few cells.
What type of collagen are found in the dermis?
Types I, III and V
What are the tension lines of an animal’s skin?
Lines determined by the orientation of collagen fibres in the dermis?
What are the two layers of the dermis?
- Superficial papillary region
- Deeper reticular region
What key components are found in the dermis?
- Blood vessels
- Lymph vessels
- Nerves
- Sensory receptors
- Hair follicles
- Arrector pili muscles
- Sebaceous + sweat glands
What is the clinical importance of tension lines?
It is easier to close and incise parallel to these tension lines.
What are the 5 layers of the epidermis?
1) Stratum corneum (TOP)
2) Stratum lucidium
3) Stratum granulosum
4) Stratum spinosum
5) Stratum basale (BOTTOM)
Can Long Giraffe Spines Bend
In which layer are keratinocytes first produced?
In the stratum basale
What happens to these keratinocytes once they have been synthesised?
Move up through the layers, towards the skin surface, differentiating as they do so
What is the function of the stratum basale?
- Provides attachment to the basement membrane
- Proliferation (constant division) of stem cells occurs here
What are the important functions of the stratum spinosum?
- A thick layer in which cells are connected by desmosomes
- Contains dendritic cells important for immune response
What is significant about to the stratum granulosum?
- Keratinocytes contain keratohyalin granules
- Keratohyalin granules contain the products needed for keratinisation (the process of turning keratinocytes-> corneocytes).
Where is the stratum lucidium found?
- A clear layer
- Found only in thick, non-hairy skin
What is the function of the stratum corneum?
- Thickest layer
- Waterproof cell membrane
- No organelles/ nuclei
- Few desmosome attachments so cells can slough off
- Made of corneocytes
What other cells are present in the cutis as well as keratinocytes and corneocytes?
- Melanocytes
- Dendritic cells
- Merkel’s cells
What is the function of dendritic cells and Merkel’s cells?
- Dendritic cells aid immunity
- Merkel’s cells form touch receptors
What is the function of melanocytes and where are they found?
- Produce melanin to protect the DNA in the nucleus from UV radiation
- Found in the stratum basale
Which parts of the developing embryo are responsible for forming the epidermis, the dermis and the melanocytes?
- Epidermis formed from ectoderm
- Dermis formed from mesoderm
- Melanocytes made from neural crest cells
What do the dorsal and ventral branches of the spinal nerve innervate in relation to the skin?
- Dorsal branches supply the dorsal cutaneous nerves innervating the dorsal skin
- Ventral branches supply the ventral and lateral cutaneous nerves innervating the ventral and lateral skin.
Nerves from which plexus help to innervate the skin of the limbs?
- brachial plexus
- lumbar plexus
What are autonomous zones?
Non-overlapping regions supplied by a single nerve
Why are autonomous zones important?
Important for successful local anaesthesia and diagnosis of peripheral nerve lesions
What are the 3 main structures used to detect sensory information in the integument?
- Free nerve endings (detect pain and itch)
- Merkel cells (detect touch and pressure)
- Pacinial corpuscles (detect deep pressure)
What 3 things are innervated by sympathetic motor neurons in the integument?
- Blood vessels
- Sweat glands
- Pilomotor apparatus
1) How does the common integument provide protection of the body?
2) How about protection from radiation?
1) Fat, collagen and keratin help to provide physical protection
2) Melanocytes aid protection from radiation
What epidermal organs help to provide protection?
Horns and claws
In what 3 ways does the outer integument aid immune defense?
1) Acts as a physical barrier to infection
2) Immune cells present in the skin
3) Antimicrobial properties in skin gland secretions
How does the outer integument help with sensing the environment?
Has pressure receptors/ pain receptors/ temp. receptors/ tactile hairs
How does the outer integument aid with thermal regulation?
- Sweating
- Piloerection
- Controls blood flow to skin
- Insulation by fat
1) How does the skin aid with storage and secretion?
2) How does it aid with communication and camoflague?
1) - Fat stores energy, water and vitamins.
- Glands excrete water and electrolytes
2) - Scented substances released from glands
- Raising of hair/ feathers
- Pigmentation
What is the significance of the selective permeability of skin?
- Some medications can be absorbed across the skin
- Some species use their skin for respiration
