Integument Flashcards
6 structures derived from skin:
-hair
-nails
-glands
-hooves
-horns
-scales
12 functions of skin
-capture prey
-calcium homeostasis
-protection from parasites & microbes
-immune response
-protection from UV
-locomotion
-social functions
-secretion
-sensory reception
-temperature regulation
-physical protection
-environmental barrier
Areas of skin that go through wear and tear are highly
Cornified
4 social functions of skin
-pigmentation
-hair and feathers
-horns
-glands (pheromones)
3 ways skin regulates temperature
-hair and feather
-sweat glands
-cutaneous blood supply (vasoconstriction/dilation)
2 ways the skin protects against parasites and microbes
-keratinisation (physical barrier)
-sebum (oily secretion “seals” skin and stops bacteria from dividing)
Vitamin D is produced by ___ in response to ___. It is then converted to ___ which regulates ___ in the body.
Skin; sunlight. Calcitriol; Calcium
2 layers of skin
-epidermis (outer layer)
-dermis (inner layer)
Epidermis is derived from the ___ while dermis is derived from ___
Ectoderm; Mesoderm
Hypodermis (4)
-not formally “skin”
-loose connective tissue layer
-attaches skin to underlying fascia, muscle, and bone
-contains Adipocytes
Appendages are __ and consist of ___
-keratinsied
-hair, horns, hooves
Outer layer of skin is called
Epidermis
Epidermis (5)
-outer layer of skin
-stratified squamous epithelium
-keratinised
-avascular (O2 and nutrients derived from Dermis)
-4-5 layers
5 layers of the epidermis
-stratum basale/germinativum
-stratum spinosum
-stratum granulosum
-stratum lucidum (not present all the time, only in heavily keratinized skin)
-stratum corneum
The most outer layer of the epidermis is
Stratum corneum
The most inner layer of the epidermis is
Stratum basale/germinativum
Which layer of the epidermis is ONLY present in heavily keratinised skin (ie. footpads, teats, planum nasale)
Stratum lucidum
Stratum baseale/germinativum (5)
-innermost layer of the epidermis
-cuboidal or columnar cells
-mitosis
-separated from dermis by basal lamina
-contains desmosomes and hemidesmosomes
Stratum spinosum (4)
-thickest layer of the epidermis (especially in hairless areas)
-large polyhedral cells become flatter
-cell separation increases, making desmosomes highly visible (cells appear “prickly”
-also called prickle cell layer
Stratum granulosum (3)
-thin layer of flattened cells
-most superficial cells lack a nucleus
-cells contain keratohyalin (precursor to keratin)
Which layer of the epidermis is also called the prickle cell layer
Stratum spinosum
Stratum corneum (4)
-dead cells (no nuclei / organelles)
-cells filled with keratin
-surface cells are sloughed off
-thick layer in areas subject to wear and tear
Stratum lucidum (7)
-layer of epidermis only found in areas that are heavily keratinised
-clear, translucent layer
-cells are dead and lack organelles
-may be water repellent
-eleidin replaces keratohyalin (derivative of keratin)
-found in footpads, planum nasale, and teat
-reduces friction and shear forces between the granulosum and corneum layers
Four cell types of the epidermis
-keratinocytes
-melanocytes
-langerhans cells
-merkel cells
Keratinocytes (3)
-produced from stem cells in the stratum basale
-most abundant epidermal cell type
-progressive keratinization
Melanocytes (3)
-found in the stratum germinativum/basale , root sheath of hair, and ducts of glands
-contain melanin bound in melanocytes
-vary in number and distribution depending on species, season, sun exposure
Eumelanin produces a ___ color while phaemelanin produces ___
Brown-black; yellow-red
Skin pigmentation occurs when
Melanin contained in melanosomes is transferred to keratinocytes
Melanin is produced via
Oxidation of the amino acid tyrosine
A mutation in tyrosinase is produces
The most common form of albinism
Albinism (3)
-mutation in enzyme tyrosinase
-autosomal recessive
-skin, hair, and eyes have little to no melanin
Albinism produces __ colored eyes while leucine produces ___ colored eyes
Red; blue
Leucism (3)
-failure in differentiation or migration of neural crest cells
-affects all pigment cells, including melanocytes
-exception: cells of the retina
The antigen presenting cells of the epidermis are called
Langerhans cells
All layers of the epidermis contain Langerhans cells, except
Stratum corneum
Langerhans cells (4)
-derived from bone marrow
-first line of defence in epidermis
-most common in upper layer of stratum spinosum
-antigen presenting cells —> immune function, phaghocytose antigens and present them to T lymphocytes
Merkel cells (4)
-common origin with Schwann cells
-lobed, irregular nuclei
-found in stratum basale/germinativum, especially in planum rostrale/nasale and the external root sheath of sinus/tactile hairs (ie. whiskers)
-contain mechanoreceptors for touch
The two layers of the dermis are
-papillary layer
-reticular layer
Directly beneath the epidermis is the
Papillary layer of the dermis
Dermis (5)
-connective tissue layer
-few cells
-amorphous ground substance
-collagen, reticular, and elastin fibres—> proportion depends on location and age of animal
-two layers
Papillary layer of dermis (3)
-underlying the epidermis
-loose connective tissue
-thin
Reticular layer of the dermis (3)
-continuous with hypodermis
-irregular dense connective tissue
-thick
The loose connective tissue layer of the dermis is called the
Papillary layer
The irregular dense connective tissue of the dermis is called the
Reticular layer
In thick skin, the junction between the dermis and epidermis consists of (2)
-epidermal pegs (epidermis bends down to dermis)
-dermal papillae (dermis projects into epidermis)
Collagen and reticular fibres in the dermis provide
Strength
The dermis contains (8)
-fibroblasts and migratory connective tissue cells (ie. macrophages, mast cells/histiocytes, plasma cells)
-collagen and reticular fibres
-elastin fibres
-blood and lymph vessels
-nerves
-sebaceous and sweat glands
-hair follicles
-smooth and skeletal muscle continuous with hypodermis
When the epidermis bends down into the dermis, it is called
Epidermal pegs
The subcutis is also called the
Hypodermis
When the dermis projects into the epidermis, it is called
Dermal papillae
Hypodermis (5)
-loose connective tissue
-anchors skin to underlying structures
-variable amounts of adipose tissue (panniculus adiposus)
-variable amounts of smooth muscle
-may contain striated muscle for voluntary movement of the skin (ie. cattle and horses twitching)
Hair is a
Flexible fibre composed of keratinised (dead) epithelial cells
Hair is formed within a
Hair follicle in the epidermis
The hair bulb generates
Hair
Hair bulb contains
Matric cells that form an epithelium over the papilla
Papilla contain
Blood capillaries
Within the hair follicle, the root of the hair is surrounded by (2)
-inner root sheath
-outer root sheath
Hair consists of (3)
-cuticle
-cortex
-medulla
The free part of a hair is called the
Shaft
The portion within the hair follicle is called the
Root
What are the 3 zones of hair, what are they produced by?
-medulla
-cortex
-cuticle
Produced by the Matrix
The medulla of hair contains
Cuboidal cells
The cortex of hair contains (2)
-densely packaged squamous keratinised cells
-melanin
The cuticle of hair contains
Single layer of overlapping squamous cells
The shape and size of the hair cuticle is
Species specific
Surrounding the cuticle of the hair is the
Inner root sheath
3 layers of the inner root sheath
-root sheath cuticle (cells interdigitate with hair cuticle)
-huxley’s layer (1-3 layers of dark staining cuboidal epithelium)
-henle’s layer (outer, single layer of flattened cells)
The inner and outer root sheaths are produced by the
Matrix
The glassy membrane
Separates the outer root sheath and the dermis
The outer root sheath (3)
-surrounds the inner root sheath
-contains many lagers of cells
-resembles stratum spinosum (prickle cell layer)
The dermal root sheath is
The area of the dermis adjacent to the hair follicle, containing fibres and cells
Associated with some hair follicles are
Sebaceous and apocrine sweat glands
Arrector pili muscle (3)
-smooth muscle
-erects hair for insulation an display
-attached to the dermal root sheath and inserts into the reticular layer of the dermis
Hair that are modified for sensory function (ex. Whiskers) are called
Sinus (Tactile) Hairs
Sinus (tactile) hairs (4)
-follicle extends deep into hypodermis
-used for sensory function
-inner and outer tooth sheaths are surrounded by a blood filled sinus
-pressure on the hair transmitted to blood sinus which passes signal to nerve endings in the sinus wall
Skin appendages are mostly
Keratinised structures of epidermal origin
7 types of skin appendages
-tori (pads)
-scales
-hair
-horns
-antlers
-claws/nails
-hooves
Tori skin appendage (3)
-aka the pad
-contact surface of extremities
-consists of epidermis, dermis, subcutaneous cushion
In the horse, the carpal/tarsal torus, metacarpal/tarsal torus, and digital torus are commonly called
Chestnut, ergot, frog, respectively
Scales are formed by
Highly keratinised stratum corneum over a fold of skin
Pangolids are
The only mammal with scales!
Guard or primary hairs (4)
-form the topcoat
-long
-thick and strong
-contain a cortex, medulla, and cuticle
Wool or secondary hairs (4)
-form the undercoat
-short
-fine, less strong
-lack a medulla (ie. ONLY a cortex and cuticle)
The fleece of sheep is entirely
Wool or secondary hairs
The juba and cirrus cordae are
Areas of very long, strong hairs in the horse (ie. mane and tail, respectively)
Hair follicles can be classified as (4)
-primary
-secondary
-single
-compound
Primary hair follicles (4)
-large diameter
-extend into reticular layer of dermis
-contain secabeous and apocrine sweat glands
-contain arrector pili muscle
Secondary hair follicle (5)
-small diameter
-superficial in dermis
-may have sebaceous glands
-lack apocrine sweat glands
-lack arrector pili muscle
A single hair follicle is
A single hair originating from a follicle
Compound hair follicles
Several hairs sharing a common follicular opening (usually one primary and several secondary hairs)
Horse, cow, and buffalo hair follicles are
Evenly spaced single follicles
Pig hair follicles are
Single follicles in clusters of 3
Dog hair follicles are
Compound follicles in clusters of 3
Cat hair follicles are
Compound follicles in clusters of 5 surrounding one single follicle
Hair growth is ___ and passes through __ stages
Cyclical; 3
Three stages of hair growth
-anagen
-catagen
-telogen
Anagen hair growth phase (2)
-active growth phase
-matrix cells of bulb divide
Catagen hair growth phase (5)
-hair bulb begins to regress
-matrix cells stop divine
-follicle shrinks
-dermal papillae shrink
-bulb fuses to hair shaft
Germ cells surrounding the base of hair are responsible for
Forming a new follicle
Telogen hair growth phase (3)
-resting phase
-hairs have a club-shaped base —> called Club Hairs
-club hairs remain in follicle until pushed out by new growth
Hair follicle stem cells are located in ___ and contribute to __
-outer root sheath
-follicle regeneration and growth during anagen
Active hair growth phase is called
Anagen
Resting air growth phase is called
Telogen
Shedding occurs during ___ hair growth phase and is usually ___
Anagen; seasonal
Claws (3)
-hard keratin structure
-produced by epidermis over 3rd phalanx
-consist of corium, claw plate, claw fold, and hyponichium
The area of the claw called the “quick” is called
The corium
The sole of the claw is called the
Hyponichium
Cat claws (2)
-can withdraw into pockets of skin via medial and lateral dorsal elastic ligaments
-contraction of deep digital flexor extends the claws
Horns are present in
Both sexes
Horns (5)
-keratin structures produced by epithelium
-permanent structures
-periosteum is continuous with corium
-corium determines length, size, and shape
-consists of tubular and non-tubular horn
Nerve supply of horns (2)
-corneal branch of zygomaticotemporal nerve
-goat has additional nerve (infratrochlear nerve)
Blood supply of horns is via
The dorsal and central branches of the cornual arteries
Antlers are made of ___, not ___
Bone; keratin
Antlers (4)
-branched
-restricted to males (exception: caribou and reindeer)
-produce and shed annually
-growth occurs from the pedicle on frontal bone
Soft keratin of antlers is called
Velvet
Shedding of antlers
Decrease in daylight —> decrease in testosterone —> decrease in calcium —> blood supply restricted —> sloughing of velvet —> bone of antler dies
Skin glands are formed as
Downgrowth of the epidermis into hypodermis/dermis
General distribution skin glands include (2)
-sebaceous glands
-apocrine and Merocrine sweat glands
Which glands are usually associated with the hair follicle
Sebaceous and apocrine sweat glands
3 modes of exocrine secretion and an example
-Holocrine (sebaceous glands)
-Merocrine/Eccrine (sweat glands)
-Apocrine (sweat glands)
Sebaceous glands (5)
-simple branches or compound, alveolar (acinar) glands
-Holocrine mode of secretion
-product = sebum (made of cholesterol and triglycerides)
-pilosebaceous canal lined with stratified squamous epithelium
-basal cells contain melanocytes
The pilosebaceous canal can become ___ in response to ___
Hyperkeratinised (leading to atrophy) in response to inflammation
Sebaceous glands aggregate in the
-eyelids
-lips
-external ear
Five functions of Sebum
-bacteriostatic and fungistatic
-reduces water loss
-vitamin D precursor
-distribution of pheromones
-lanolin in wool
Apocrine sweat glands are restricted to
Primary hair follicles
Apocrine sweat glands (5)
-simple coiled tubular glands
-located in dermis or hypodermis, below the hair papilla
-apocrine mode of secretion
-consists of myoepithelial cells
-serous secretion
Two main roles of apocrine sweat glands
-thermoregulation (especially in horses and cattle)
-distribution of pheromones
Horse apocrine sweat glands
Contains high levels of albumin and a unique protein called latherin
Merocrine sweat glands (7)
-simple coiled tubular glands
-consists of myoepithelial cells
-deeper in dermis/hypodermis than apocrine sweat glands
-independent of hair follicle
-very watery secretory product
-functions are unknown
-ONLY found in digital tori and nasolabial region
Sweating is regulated via the release of
Adrenaline and acetylcholine
Control of sweating is done by the ___ and ___ in response to ___
Hypothalamus and brain stem; heat, exercise, and stress
While sweating, secretory cells control ___ while mypepithelial cells control ___
Rate of production; rate of expulsion
External auditory meatus (4)
-specialized skin gland
-sebaceous and apocrine glands
-produces cerumen (ear wax)
-excess = otitis externa
Two specialized skin glands of the upper and lower eyelids are
-meibomian gland
-glands of moll
Meibomian glands are ___ whereas glands of Moll are ___
Sebaceous; apocrine
Meibomian glands can form (2) that are removed via
-cysts
-adenomas
-surgery
Mental organ is found in the ___ and is used for ___
-intermandibular space (chin) of the pig
-tactile and marking function
The infraorbital sinus is found in the ___ and its function is ___
-pouch of thin skin rostral to the eye in sheep (more pronounced in rams)
-territorial marking
The circumoral gland is found in the ___ and used for ___
-upper and lower lip of the cat
-territory (and people) marking
The inguinal pouch is found in the ___ and used for ___
-folds of skin under udder or near scrotum in the sheep
-communication (where animals have been lying, location of udder) and reduces friction between udder and thigh
Horn glands are found in the ___ and used for ___
-goat (larger in billies)
-produces a strong odour during breeding season
Prenuptial gland is significant in ____. Studies in ___ show they have a role in ____
-stallions and boars
-mice; attracting females
Tail glands are also called ___ and are found in ___
-supracaudal glands
-dogs and cats
Tail glands can become ___ in the dog
Hyperplastic and/or infected
Supracaudal glands are found on ___ and used for ___
-dorsum of tail in dogs/cats
-territorial marking
Mammary glands (5)
-highly modified apocrine sweat glands
-compound tubulo-alveolar glands
-apocrine secretion = fats
-Merocrine secretion = proteins and carbohydrates
-myoepithelial cells control milk let down
Anal sacs are
Invaginations of the skin at the junction of hair and non-hairy skin
In the dog, the glands of the anal sacs are
Apocrine
In the cat, the glands of the anal sacs are
Apocrine and sebaceous
Glands of the anal sacs discharge secretion
At defecation for territorial marking
True or false: in dogs, the anal glands can become impacted
False. The anal sacs become blocked, NOT the glands
Circumanal glands (5)
-specialized skin glands in the perianal skin of dogs
-superficial portion = sebaceous glands
-deep portion = hepatoid cells with unknown function
-used for dog-to-dog communication
-common site of neoplasia
Interdigital pouch is found in ____, secretes ___ and is used for ___
-skin pouches at the dorsal tip of interdigital space in ruminants
-waxy secretion (mix of sebaceous and Merocrine glands)
-trail marker
Carpal glands are ___ found in ___ and used for ___
-merocrine glands
-pig and cat
-boars mark sows at mating
Blood supply to the skin lies in the ___ and forms ___
-dermis
-3 interconnected plexi
Three interconnected plexi of blood supply to skin
-deep plexus in the hypodermis/deep dermis
-intermediate plexus in the reticular layer of dermis
-superficial plexus in the papially layer of dermis
Lymph vessels arise from ___ and drain into ___
-lymph capillaries in the papillary layer of the dermis
-subcutaneous lymphatic plexus
Cutaneous Innervation is done via (3)
-Sympathetic Fibres (smooth muscle of blood vessels, arrector pili, and myoepithelial cells)
-Somatic Afferent (Sensory) in the dermis/epidermis for touch, pain, temperature, and pressure
-Somatic Efferent (Motor) is striated cutaneous muscle fibres that are rarely found —> horses and cattle twitching to remove flies
Three types of sensory nerve endings in the skin
-free nerve endings
-encapsulated endings
-lamellated endings
Free nerve endings (4)
-fine nerve terminals lacking myelin
-receptors for temperature, touch, and pain
-innervate hair follicles
-abundant in sinus (whisker) hairs
Encapsulated endings (3)
-touch receptors
-terminals surrounded by connective tissue cells
-example: Meissner’s corpuscles
In the skin, the receptor for temperature/touch/pain is
Free nerve endings
Lamellated endings (3)
-concentric layers of connective tissue cells
-found in footpads
-pressure receptors
Receptor for touch in the skin is
Encapsulated endings (Meissner’s corpuscle)
Receptor for pressure in the skin are
Lamellated endings
