Integumentary System Flashcards
What is the integumentary system?
The skin and its adnexal structures (hair and glands), horns, hoofs, claws, and other epithelial modifications
What molecule in the integumentary system helps it to act as a protective barrier?
Keratin
In what ways does the integumentary system act as a protective barrier
It reduces water loss, invasion by microorganisms, and abrasive trauma
What is skin?
An outside covering of an animal
What is skin continuous with?
Mucous membranes in the oral, anal, and urogenital orifices
Vestibule (inside) of the nostril
Palpebral fissure (area between eyelids)
What are the three layers of the skin?
Outer epidermis, the dermis, and the subcutaneous layer
What is the outer epidermis?
The layer we can touch
Describe the structure of the tissue that makes up the outer epidermis.
Keratinized, stratified, squamous epithelium
Why does the outer epidermis being stratified help
It allows for shedding and replacement of skin cells
What is the dermis?
The layer that hair and sweat glands originate from
Describe the structure of the tissue that makes up the dermis.
Dense, fibrous, vascular, connective tissue
What is the subcutaneous layer?
The hypodermis/bottom layer of skin
What is contained within the subcutaneous layer and what is its purpose?
Adipose/fat tissue
It insulates and absorbs shock
What determines how much adipose is in the subcutaneous layer?
The species of the animal
What is skin characterized by?
The mucocutaneous junction
In what two ways can skin thickness differ?
The species and the location on an individual
Where on an individual is skin the thickest?
Where it is the most exposed, like the back
Where on an individual is the skin the thinnest?
Where it is more protected, like the groin
How does skin adherence to structures beneath it vary?
By location on the individual
What are the three types of subcutaneous injections and what are the angles that they enter the skin at?
Intramuscular 90 degrees, subcutaneous 45 degrees, intradermal 10-15 degrees
What does an intramuscular injection penetrate and what is special about this kind of injection?
It penetrates the muscle
The length of the needle will vary based on species due to the varying thickness of adipose in the subcutaneous tissue that the needle has to pass through to reach the muscle
What does a subcutaneous injection penetrate?
The subcutaneous tissue
What does an intradermal injection penetrate?
The dermis
Where is the blood supply in the skin?
Only at the most basal layer of the epithelium/epidermis to help aide with production of new cells, which die off when they get further from the blood supply
What is the stratum corneum?
The most superficial layer of the epidermis that consists of layers of dead, flattened cells and has a smooth texture
What is the stratum lucidum?
A small layer of poorly stainable cells below the stratum corneum that is not always present
What is the stratum granulosum?
The layer below the stratum corneum (and stratum lucidum) that consists of spindle-shaped cells full of basophilic keratohyalin granules
What is the function of keratohyalin granules in the cell?
The cells in the stratum granulosum fill up with them, which kills the nucleus and causes the cytoplasm and organelles to go away, leaving the cells with no way to reproduce, so they dieI
What is the stratum basale?
A mitotically active layer of cuboidal or columnar cells that follow the shape of the dermis below it because it’s closely attached
Why is the stratum basale mitotically active?
Because it’s making cells to replace the cells that are dying off and being replaced
Where is the dermis in relation to the epidermis?
Below it
What are most of the cells in the epidermis?
Keratinocytes
What is a melanocyte?
A cell attached to the dermis that produces melanin, or pigment, that is absorbed into keratinocytes and provides protection from UV raysFr
What is a Merkel cell?
A cell close to nerve endings in the epidermis that contains hormones
What makes dead cells tough?
They’re filled with keratin
What happens to epidermis cells as they move further away from nutrients?
Cells flatten and die, but they leave a dense mat of their primary constituent- keratin
What is the process of drying and hardening the superficial cells called and what does it do?
Keratinization and cornification
It allows the skin to be tough and resistant while drying
What does the dermis contain?
Blood, sensory nerves, and glands
How does the dermis interact with the epidermis?
It interdigitates (interweaves) itself with the epidermis
What are the dermal papillae?
The dermal papillae are the interdigitating parts of the epidermis
What type of tissue makes up the dermis?
Fibrous connective tissue
What is the function of the dermis?
To support and strengthen skin
What is the papillary layer?
The layer containing the dermal papillae
What is the reticular layer?
The layer below the reticular layer that consists of 80% dense, irregular connective tissue
How do melanocytes interact with the dermis?
The melanin they produce is stored in melanosomes
What is a blister?
A disruption between the epidermis and dermis at the dermal papillae
How is a blister formed?
Epidermis is forced in a direction it’s not supposed to go, and the dermis isn’t made to go with it, so it rips
What is a callus?
Thickened stratum corneum
How does a callus form?
Repeated blisters prompts a thicker layer to form to help protect the dermis
Is the hypodermis a true layer?
No it’s a subcutaneous fat
What does hypodermis do?
Separates skin from muscle
What does the hypodermis have a lot of?
Connective tissue
What is the main type of tissue found in the hypodermis?
Areolar connective tissue
What is the variable amounts of fat in the hypodermis called?
Panniculus adiposus
What makes up paw pads?
Thick, tough skin with a thick layer of stratum corneum covering layers of fat and connective tissue
What does the increased adipose in paw pads do?
Provides a cushion
What are the purpose of paw pads?
Provide protection and reduce noise so predators can sneak up on prey
What is the planum nasale?
The top of the nose
The muzzle in horses and cows
How do different species keep the planum nasale moist?
In dogs, it is not glandular and is kept wet through nasal secretions and licking
In cows, sheep, and pigs, it is glandular with the glands keeping it moist
What are the three types of hair?
- Primary/Guard hairs
- Secondary/Undercoat/Wool hairs
- Tactile hairs
What is the structure of primary/guard hairs?
Straight or arched and thick and long
What is the function of primary/guard hairs?
Protect the undercoat and provide waterproofing
What is the structure of secondary/undercoat/wool hairs?
Soft and short, can be wavy or bristled
What is the function of secondary/undercoat/wool hairs?
Trap air and insulate
Where can tactile hairs be found?
As whiskers and throughout the coat
What surrounds the root of a tactile hair follice?
Touch receptors
What does the color of hair depend on?
The quantity and type of melanin (not the same type as skin pigmenting) produced by melanocytes in the papillae
What are the types of hair melanin and what colors do they produce?
Phenomelanin- yellowish and red colors
Tyrosine melanin- brown and black colors
The proportion of what type/s of hair depends on species?
Primary/guard hairs and secondary/undercoat/wool hairs
What is a hair follice?
A modification of the epidermis that an individual hair arises from
How is a hair follicle embedded in the skin?
It invaginates the epidermis and originates from it
How can you tell what layer of the epidermis the hair follicle is in?
The cells around it indicate which layer
What is the outermost layer of the hair?
The cuticle
What is the cuticle’s structure and what does it allow?
It has overlapping cells that form scales and allow for felting
Some species don’t have scales
What is the middle layer of the hair?
The cortex
What is the structure of the cortex?
Overlapping diamond-like structures
What is the innermost layer of the hair?
The medulla
What is the medulla made of?
Soft keratin
How is the medulla affected over time?
The medulla is where hair pigmentation is seen. With time, more air spaces appear in the medulla, leaving less room for dying, and giving a grey appearance
What is the arrector pili muscle?
A small, smooth muscle bundle, that when contracts, straightens the hair toward 90 degrees
Describe a hair follice.
A double-layered root sheath that surrounds the hair and ends in a hair bulb in the epidermis
How is the hair generated?
By the division of epithelial cells that cover the dermal papilla
What is the most superficial layer of the root sheath?
The dermal root sheath
What is the middle layer of the root sheath?
External epithelial root sheath
What is the deepest layer of the root sheath and what does it cover?
Internal epithelial root sheath, which covers the cuticle below the surface and connects to the sebaceous gland
What surrounds the hair bulb and what does it do?
The dermal papilla, which generates the hair
From superficial to deep, what are the layers of cuticle that surround a wool cell?
Epicuticle, exocuticle, endocuticle
What are the layers of a wool cell, from largest to smallest?
Cell, macrofibril, matrix, microfibril, protofibril, alpha-helix
What does wool grade judge?
Diameter, crimp, and length of the fibers
What is the most desirable wool fiber?
Fine, wavy, and long fibers
What is lanolin?
A product of the subcutaneous sebaceous glands
What are two other names for lanolin?
Wool grease and wool wax
What are sudoriferous glands commonly known as?
Sweat of glands
Where are sudoriferous glands found?
Over the entire body. Sparser in pigs
What are the two types of sudoriferous glands?
Merocrine and apocrine glands
How do merocrine grands release their substances?
Through exocytosis with secretory vessels
What is the structure of merocrine glands?
Tubular glands with cuboidal epithelium surrounded by myoepithelium
How do merocrine glands expel substances?
By contracting to squeeze liquid onto the skin
What is myoepithelium?
Cells that surround glands and respond to hormones to contract and squeeze the cells to force the substance out onto the skin
Why do salivary glands use exocytosis instead of destroying the cell?
Since the glands are already in a spot with a lot of stress, they’re being damaged enough. If they’re damaged any more, they’ll waste too many resources repairing themselves and enough saliva won’t be produced
What areas of the body lack sweat glands?
Modified epithelial structures like hooves and horns
How does an apocrine gland get rid of its substances?
By removing the top portion of the cell to remove the substances within
What type of gland is thought to be a modified tubular sweat gland?
The mammary gland, which is a modified apocrine gland
What is another word for sebaceous glands?
Holocrine glands
What do sebaceous glands secrete?
An oily product called sebum
How is sebum produced?
By completely disintegrating the epithelial cells of the glands
How do holocrine cells get rid of their substances?
A whole cells moves away, disintegrates, and is replaced so it can repeat
What do excretory products do in holocrine glands?
They accumulate in the cell until the whole thing ruptures and the product is released
What aids holocrine glands in releasing their substances?
Contraction of the arrector pili muscle
Where do holocrine glands open and where are some examples of where they can be found?
They open directly onto the skin’s surface and can be found in the ear canal, anus, penis, prepuce (foreskin or clitoris), vulva, and tarsal glands in the eyelid
What is the defining characteristic of ungulates?
Presence of a well-developed hoof associated with the distal phalanx
What is the periople?
A thin waxy layer that covers the hoof
What makes up the bulk of thickness of the hoof?
The hoof wall
How is the hoof wall produced?
From the coronary band, which is a belt of epidermis
How do the hoof wall and the coronary band (corium) interact?
They are interdigitated
What are the interdigitations of hoof wall and corium called?
Laminae
What are the two types of laminae and where are they located?
The insensitive laminae is part of the epidermis
The sensitive laminae is part of the corium
What are the two parts of the hoof that make contact with the ground?
The horny sole and the soft hoof bulbs
What species has a more extensive hoof bulb?
Horses
What is the digital cushion?
The shock-absorbing modification of the hoof that bears a significant portion of the animal’s weight
What is the keratinized V-shaped frog?
A feature found only in the equine hoof that is more flexible than the sole, but harder than the bulbs of other ungulate species
What is acute laminitis?
When a separation gap is present either between the epidermal (insensitive) laminae and the phalanx or between the phalanx and the sole
What is severe laminitis?
When there is a wide gap between the phalanx and the insensitive laminae and the phalanx has rotated downward
What are dewclaws?
Accessory structures that don’t typically touch the ground
What digits do dewclaws correspond to in ruminants?
II and V
Can dewclaws bear weight in ruminants?
No. They have little clinical significance
In what way are porcine dewclaws developed?
They have three phalanges and a small developed hoof
Can porcine dewclaws bear weight?
Yes, occasionally
What are horns?
Keratinized epidermal tissue
What is significant about a fully developed horn?
It’s very close to a lot of nerves and is highly vascularized
What is the horn itself made of?
Dense keratin
Where does the horn elongate from?
The base
What does the horn’s corium surround and blend with?
It envelops the cornual process and blends with periosteum
What is the epikeras?
A soft type of horn that covers the base of the horn’s surface and extends toward the apex/point of the horn
What does the epikeras resemble?
The periople of the hoof
What is the cornual nerve?
A nerve that follows the edge of the temporal bone in the skull to the base of the horn
What is the auriculopalpebral nerve?
A nerve that crosses the zygomatic arch
What is the diverticulum of frontal sinuses?
An empty air space below the corium and periosteum that connects to the sinuses
What do antlers do yearly?
Grow and shed
What do antlers lack?
A central core and internal blood supply
Where do antlers receive their blood supply from?
The outer velvety covering
What happens when the antler growth is complete?
A ring of cartilage forms at the base and cuts off blood supply to the velvet and the velvet dies off
What does the loss of velvet do to an antler?
Causes it to harden
What are antlers used as?
A weapon, a status symbol, and an attractive male attribute
What happens to antlers with time?
The bony connection to the skull breaks down and the antlers fall off, allowing new growth to begin
What are cutaneous pouches in sheep?
Pouches that contain sebaceous glands
Where are cutaneous pouches found in sheep?
Rostral to the eye, between the digits and proximal to the hooves (interdigital), and in the groin
What do sebaceous horn glands in goats do?
Increase secretion during breeding season
Where are the sebaceous carpal glands found in pigs?
On the mediopalmar aspect of the carpus
Where are chestnuts and ergots found in horses?
As growths on the limbs
