Integumentary Flashcards
What is the general texture and thickness of the epidermis in avian skin?
The epidermis in avian skin is loose, dry, and quite thin.
What are the specific layers of the avian epidermis from innermost to outermost?
The layers of the avian epidermis are:
a. Stratum basale
b. Stratum intermedium (also called stratum spinosum)
c. Stratum transitivum (also called stratum granulosum)
d. Stratum corneum
In avian skin, what term collectively refers to all the layers of the epidermis except the stratum corneum?
The term ‘stratum germinativum’ is used to represent all the epidermal layers except the stratum corneum.
What metabolic function is the avian integument known for and why?
The avian integument is referred to as an organ of lipogenesis because it contains extensive amounts of lipids in the epidermal cells in most avian species.
What types of lipids does the avian epidermis synthesize?
The avian epidermis synthesizes triacylglycerols, phospholipids, wax esters, free fatty acids, monoacylglycerols, and diacylglycerols.
What type of fibers compose the dermis in avian skin?
The dermis in avian skin is composed of fine collagenous fibers.
In avian skin, how defined is the papillary region of the dermis?
The papillary region of the dermis in avian skin is not well defined.
What kind of immune-related tissue is found extensively in the avian dermis?
Extensive lymphoid tissue is present in the avian dermis.
How are the dermis and hypodermis of avian skin subdivided?
The dermis and hypodermis are subdivided into:
Stratum superficiale
Stratum profundum, which includes:
Stratum compactum (dense layer)
Stratum laxum (loose connective tissue containing fat, large blood vessels, smooth muscle, and follicles)
Lamina elastica (elastic lamina of the dermis)
What is the origin of feathers in birds, and how are they similar to mammalian hair?
Feathers are of epidermal origin and, like mammalian hair, develop within a follicle.
What types of muscles are associated with each feather follicle in birds?
Each feather follicle is associated with several smooth muscles with elastic tendons.
What type of muscle allows voluntary movement of the skin in response to stimuli in birds?
Cutaneous striated muscles allow voluntary movement of the skin in response to stimuli.
What is another name for the uropygial gland in birds?
The uropygial gland is also known as the oil gland or preen gland.
What is the only cutaneous gland in birds, and in which species is it especially well-developed?
The uropygial gland is the only cutaneous gland in birds and is especially well-developed in aquatic species.
What structural units make up the uropygial gland, and where do they empty?
The uropygial gland consists of numerous sebaceous adenomeres that continue into a common duct or sinus and empty on the surface on a common papilla.
What type of skin gland is the uropygial gland considered, and how is its secretion released?
The uropygial gland is considered a specialized sebaceous skin gland; its secretion is released via holocrine secretion.
How is the secretion of the uropygial gland regulated in birds?
The secretion of the uropygial gland is regulated by hormonal influences.
What are the three main functions of the combined sebum from the uropygial gland and lipids from epidermal cells in birds?
They act as antibacterial agents, prevent feather keratin from drying out, and provide waterproofing.
What specialized epidermal structures are present in birds?
Specialized epidermal structures in birds include scales, toe pads, claws, wattles, spurs, and combs.
Which avian structures are comparable to the mammalian claw?
Claws, spurs, and beaks in birds are comparable to the mammalian claw.
What avian structure is similar to the footpads of carnivores?
The toe pads of birds are similar to the footpads of carnivores.
To what are avian scales comparable, and where are they found in birds?
Avian scales are comparable to those of reptiles and occur on the legs of all birds and on the wings of penguins.
What structures in birds are skin diverticula and what do they contain?
Wattles and combs are skin diverticula that contain extensive vasculature, mucous connective tissue, and fats.
What additional type of tissue may be found in wattles and combs of some bird species, such as turkeys?
In some birds like turkeys, erectile tissue may also be present in the wattles and combs.
What is first intention healing in avian skin repair?
First intention healing occurs when the skin is disrupted by a clean incisional wound and is closed immediately.
What is second intention healing in avian skin repair?
Second intention healing results when a wound with tissue loss is allowed to heal spontaneously without or with minimal surgical intervention.
What is third intention healing in avian skin repair?
Third intention healing is a combination of first and second intention healing.
What are hairs classified as in terms of skin origin?
Hairs are modified epidermal structures.
How common are hairs within the integumentary system?
Hairs occur variably within the integumentary system.
What are the main functions of hairs in the integumentary system?
The functions of hair include insulation, protection, and sensory reception.
How do hairs develop within the skin layers?
Hairs develop as localized thickenings of the epidermis that invaginate into the underlying connective tissue and may extend into the hypodermis.
What is the outermost layer of the hair follicle and what is its origin?
The outermost layer is the connective tissue sheath, which originates from the dermis and is oriented circumferentially around the follicle.
In hair follicle structure, what is the function of the basement membrane and what is it also called?
The basement membrane, also known as the glassy membrane, separates the connective tissue from the epithelium of the follicle.
What is the external root sheath and which layers of the epidermis contribute to its structure?
The external root sheath is essentially a continuation of the stratum basale, stratum spinosum, and stratum granulosum of the epidermis.
What is the internal root sheath and which epidermal layer is it a continuation of?
The internal root sheath is a downward continuation of the stratum corneum.
What are the three named regions of the internal root sheath in the hair follicle?
The three regions of the internal root sheath are Henle’s layer, Huxley’s layer, and the cuticle of the root sheath.
In the internal root sheath of hair, what is Henle’s layer composed of?
Henle’s layer consists of a single layer of flattened cells.
In the internal root sheath of hair, what does Huxley’s layer consist of and what specific granules does it contain?
Huxley’s layer consists of several layers of cells that contain trichohyalin granules.
What is the cuticle of the internal root sheath and where is it located?
The cuticle of the root sheath is the innermost layer of the internal root sheath, made up of a single layer of cornified cells that abuts the cuticle of the hair.
What are the three main regions of the hair shaft?
The three regions of the hair shaft are:
a. Cuticle
b. Cortex
c. Medulla
What characterizes the cuticle of the hair shaft?
The cuticle of the hair shaft is a single layer of enucleated, cornified cells that interdigitate with the cuticle of the internal root sheath.
What forms the bulk of the hair shaft and what are its characteristics?
The cortex forms the bulk of the hair shaft and consists of several layers of flattened, cornified cells containing ‘hard keratin’; pigment may also be present and the intercellular spaces often contain numerous air spaces.
What is the structure of the medulla in the hair shaft, and is it always present?
The medulla, when present, consists of cornified cuboidal cells separated by air spaces. It may be absent in some hairs.
How can the cuticular, cortical, and medullary characteristics of hair be used diagnostically?
The specific characteristics of the cuticle, cortex, and medulla in hair are distinct enough to allow species identification with careful examination.
What structure marks the termination point of the hair follicle and what is its shape?
The hair follicle terminates in a cone-shaped epidermal peg called the hair bulb.
What is defined by the hair bulb in the hair follicle?
The hair bulb defines the limits of the dermal papillae.
What is the function of the dermal papillae in the hair follicle?
The dermal papillae ensure the close association of the vascular bed with the growing epidermis region.
In the hair follicle, which epidermal cells give rise to medullary cells during hair growth?
The epidermal cells at the apex of the dermal papillae give rise to medullary cells.
In the hair follicle, what do the lateral epidermal cells near the apex of the papillae form during hair growth?
They give rise to cortical cells and cuticular cells.
In the hair follicle, which cells give rise to the inner root sheath during hair growth?
The cells located at the depths of the epidermal peg give rise to the inner root sheath.
What cells in the hair follicle give rise to the outer root sheath?
The more laterally located cells of the epidermal peg give rise to the outer root sheath.
How is hair growth achieved in the hair follicle?
Hair growth is achieved by simple apposition of new cells from the depth of the follicle, similar to typical skin growth.
What is the arrector pili muscle in relation to the hair follicle, and what type of muscle is it?
The arrector pili is a sheath of smooth muscle attached to the connective tissue associated with the hair follicle and the papillary region of the skin.
Where does the arrector pili muscle attach in the skin and hair structure?
It attaches to the connective tissue of the hair follicle and the connective tissue of the skin’s papillary region.
What happens when the arrector pili muscle contracts?
Contraction of the arrector pili muscle erects the hair and expresses the sebaceous glands located between the muscle and hair follicle.
How are hairs distributed in horses and large ruminants?
In horses and large ruminants, hairs are evenly distributed on the body.
How are hairs arranged in pigs, cats, and dogs?
In pigs, cats, and dogs, hairs are arranged in groups called hair beds.
In dogs, what is a hair bed and what does it contain?
A hair bed in dogs contains 2–4 clusters of hair follicles.
What does each cluster in a dog’s hair bed typically consist of?
Each cluster usually consists of one principal (guard) hair and 3–9 auxiliary (secondary or wool) hairs.
What does the hair coat of animals reflect?
The hair coat reflects the animal’s state of health and presence of disease.
How does disease affect the appearance of the animal’s hair coat?
In disease, the hair coat may appear lusterless and dull.
What causes the dullness of the hair coat in some diseases?
Dullness results from cuticular cells not being flattened against the cortex, which impairs normal light reflection.
What are the other names for sensory hairs in animals?
Sensory hairs are also known as tactile hairs or sinus hairs.
What is the general structural comparison between sensory hairs and regular hairs?
Sensory hairs have structures similar to normal hairs.
What sensory structures are associated with sensory (tactile/sinus) hairs?
Free nerve endings and Merkel’s disks are associated with the epidermal cells and connective tissue fibers of sensory hairs.
Where are the glands of the mammalian skin generally located in relation to hair?
The glands of the mammalian skin are generally associated with hairs.
Where can the glands of the skin deposit their secretory products?
They may deposit their secretory products into the hair follicle or empty them independently onto the skin surface.
What is the origin of sebaceous glands in relation to the hair follicle?
Sebaceous glands are evaginations of the epithelial lining of the root canal.
What type of gland are sebaceous glands morphologically?
They are simple, branched alveolar glands.
What surrounds the sebaceous gland structure?
Sebaceous glands are enclosed by a basement membrane.
What is the composition of the peripheral cell layer in sebaceous glands?
The peripheral cell layer consists of either squamous or cuboidal epithelial cells.
What is the function of the peripheral cells in the sebaceous gland and what skin layer do they resemble?
These peripheral cells act as stem cells of the gland and function similarly to the stratum basale of the skin.
What type of secretion mechanism do sebaceous glands use?
Sebaceous glands are holocrine in nature.
What is the name of the secretory product of sebaceous glands, and what is its composition?
The secretory product is called sebum, and it is composed of accumulated lipids, including fatty acids and cholesterol.
What are four functions of sebum produced by sebaceous glands?
- Protects from invading microorganisms
- Minimizes water loss
- Contains precursors to vitamin D
- Keeps hair and outer skin soft and pliable
Which areas of the mammalian body lack sebaceous glands?
Sebaceous glands are absent in the footpads, hooves, claws, horns, and other similar structures.
What is another name for sweat glands?
Sweat glands are also called sudoriferous glands.
What is the structural classification of sweat glands?
Sweat glands are simple coiled tubular glands.
In which two species are sweat glands extensively developed?
Sweat glands are extensively developed in the horse and in humans.
Are sweat glands present in birds?
No, sweat glands are absent in birds.
What is the arrangement of the adenomeres in merocrine sweat glands?
The adenomeres of merocrine glands are arranged as a glomus, which is a tuft or ball-like structure.
What type of contractile cells are present in merocrine sweat gland adenomeres?
Myoepithelial cells are present in the adenomeres.
What is the primary sweat gland type in humans?
Merocrine sweat glands are the primary sweat glands in humans.
Where are merocrine glands usually found in animals (other than humans)?
They are usually restricted to the footpads of other animals.
What is the predominant type of sweat gland in domestic animals?
Apocrine glands are the predominant sweat glands in domestic animals.
In humans, where are apocrine glands primarily located?
In humans, apocrine glands are usually confined to the mammary, axillary, pubic, and perineal regions.
In cats, how extensive are the apocrine glands and where are they located?
In cats, apocrine glands are not as extensive as in other animals and are confined to the anal and oral regions, the lower jaw, and footpads.
In dogs, how are the apocrine sweat glands distributed and how functional are they?
Dogs have extensive tubular apocrine glands over the entire body, but they are apparently minimally functional as sweat glands.
What is one primary physiological function of sweat glands?
Sweat glands serve as a cooling mechanism for the body.
What type of substance do sweat glands secrete, and what is its pH nature?
Sweat glands secrete a slightly alkaline serous substance.
How does the composition of sweat in horses differ from that in other animals?
In horses, sweat is strongly alkaline and contains albuminoids, serum globulins, and some urea.
In which species are anal glands present?
Anal glands are present in the dog, cat, and pig.
What type of glands are anal glands considered as, based on their structure?
Anal glands are modified tubuloalveolar sweat glands.
Where are anal glands located in relation to the anal canal?
Anal glands occupy the submucosa of the columnar and intermediate zones of the anal canal.
Where do anal glands open into?
Anal glands open into the anus.
What is the nature of the secretion of anal glands in dogs?
The anal glands secrete lipid materials in dogs.
What type of secretion is produced by anal glands in pigs?
The secretion is mucoid in pigs.
What are anal sacs or perianal sinuses?
They are paired lateral cutaneous diverticula of the anus.
What type of epithelium lines the anal sacs?
They are lined by keratinized stratified squamous epithelium.
What do the mural glands of the anal sacs do?
Mural glands open into the anal sacs.
Where are anal sacs located in relation to the anal sphincters?
They are located between the internal and external anal sphincters.
In which animal groups are anal sacs present?
Anal sacs are present in carnivores and many rodents.
What type of glands are present in the anal sacs of dogs?
Sweat glands are present in the anal sacs of dogs.
What type of glands are found in the anal sacs of cats?
Sebaceous glands are found in the anal sacs of cats.
What is a common clinical problem associated with the ducts of anal sacs?
The ducts of the anal sac are prone to occlusion, which is often followed by infection that may require surgical removal of the sac.
What type of glands are circumanal glands?
Circumanal glands are sebaceous glands found in dogs.
What cellular feature gives circumanal glands their unique appearance?
They are composed of compact masses of cells resembling closely packed liver cells, thus the term ‘hepatoid’ is used.
What function is suspected for circumanal glands based on recent studies?
They are believed to be involved in steroid hormone metabolism.
Why are circumanal glands clinically significant in dogs?
They rank third in frequency as the site of all canine tumors.
What type of gland is the mammary gland considered to be?
It is a compound tubuloalveolar gland believed to be a modified sweat gland.
What is the mode of secretion for the lipid component of milk in the mammary gland?
Lipid secretion is by the apocrine method.
What is the secretion mode for protein and carbohydrate components in the mammary gland?
They are secreted by the merocrine method.
What main external parts make up the mammary gland?
It consists of teats and the udder.
What are the internal components of the udder?
The udder includes a capsule, interstitial connective tissue septa, secretory epithelium, and a system of excretory ducts.
What is the parenchyma-to-connective tissue ratio in actively lactating glands?
Actively lactating glands have much parenchyma and little connective tissue.
What is the parenchyma-to-connective tissue ratio in nonlactating glands?
Nonlactating glands have less parenchyma and more connective tissue.
What are the secretory portions of a lactating mammary gland?
The secretory portions include the alveoli and the initial portion of the intralobular ducts.
What type of cells are secretory cells in lactating glands, and what distinctive feature do they have?
They are columnar cells with apical blebs—protrusions into the lumen.
What gives the cytoplasm of lactating mammary secretory cells a foamy appearance?
The accumulation of fat droplets in the cytoplasm.
What does the lumen of adenomeres in lactating glands contain?
It contains corpora amylacea, composed of casein, cell debris, sloughed secretory cells, macrophages, and leukocytes.
What is the function of colostrum in some species?
Colostrum acts as a laxative and imparts immunity to nursing offspring until they develop immunologic competence.
What characterizes nonlactating mammary glands in terms of parenchyma and connective tissue?
They have fewer adenomeres (less parenchyma) and more connective tissue.
What is the shape of the secretory cells in nonlactating mammary glands?
Secretory cells are cuboidal and lack apical blebs.
What type of tissue is more extensive in nonlactating glands?
Extensive adipose tissue is present.
What type of immune cell infiltration is observed in nonlactating mammary glands?
There is extensive infiltration of lymphocytes.
Are corpora amylacea present in nonlactating mammary glands?
No, they are absent in nonlactating mammary glands.
What is another name for the secretory tubule of the mammary gland?
Intralobular duct.
What type of epithelium lines the secretory tubule/intralobular duct in the mammary gland?
Simple cuboidal epithelium.
What is the primary excretory duct of a lobule in the mammary gland?
The lobular duct.
What kind of epithelium lines the lobular duct in the mammary gland?
Simple cuboidal or columnar epithelium.
Is the lobular duct in the mammary gland secretory or nonsecretory?
Nonsecretory.
What is the primary excretory duct of a lobe in the mammary gland?
The lobar duct.
What type of epithelium lines the lobar duct of the mammary gland?
Bistratified columnar epithelium.
What additional function may the lobar duct serve in the mammary gland?
It may expand and serve as a storage area for milk.
What structure acts as a common chamber at the base of each quarter of the udder?
The gland sinus, also known as the gland cistern or lactiferous sinus.
What kind of epithelial lining does the gland sinus have in the mammary gland?
Same as the lobar duct (bistratified columnar epithelium).
What structure separates the gland sinus from the teat sinus?
A slight constriction or annulus.
Which structure in the mammary gland is continuous with the outside via the streak canal?
The teat sinus or teat cistern.
What kind of lining does the teat sinus have?
Same as the gland sinus—bistratified columnar epithelium.
What is another term for the streak canal of the mammary gland?
Papillary duct or teat canal.
What type of epithelium lines the internal and external orifices of the streak canal?
Stratified squamous keratinized epithelium.
What is the name of the longitudinal mucosal folds inside the streak canal?
Rosette of Furstenberg.
The external orifice of the streak canal is continuous with what structure?
The epidermis of the teat.
What are corpora amylacea in the mammary gland made of?
Concretions of casein (milk protein) and cell debris.
When are corpora amylacea present in the mammary gland?
Throughout lactation.
What type of connective tissue forms the capsule of the mammary gland?
Fibroelastic connective tissue.
How many quarters does the capsule divide the mammary gland into?
Four quarters.
How many teat canals per teat are present in a ruminant?
1.
How many teat canals per teat are present in a queen (cat)?
4–7.
How many teat canals per teat are present in a sow?
2–3.
How many teat canals per teat are present in a mare?
2–4.
How many teat canals per teat are present in a bitch (female dog)?
8–20.
How many teat canals per teat are present in a woman?
15–24.
What skin-derived structures are hairless and composed of thicker epidermis?
The hoof, claw, horn, and nail.
What layers compose the epidermis of the hoof?
Stratum tectorium (externum), stratum medium, and stratum lamellatum (internum).
What layer of the hoof epidermis is thick, white, shiny, and may be absent in older animals?
Stratum tectorium (externum).
What is the appearance of the stratum tectorium of the hoof?
Thick, white, and shiny.
What lies beneath the stratum tectorium in the hoof?
Stratum medium.
What two components make up the stratum medium of the hoof?
Tubular and intertubular horns.
Which layer forms the bulk of the hoof wall?
Stratum medium.
Which layer of the hoof epidermis is in contact with the dermis (corium)?
Stratum lamellatum (internum).
What features does the stratum lamellatum present?
Primary epidermal papillae that give off secondary epidermal papillae.
What is the function of the primary and secondary epidermal papillae in the stratum lamellatum?
They interdigitate with the corresponding primary and secondary laminar corium to give a lamellated appearance.
What additional structures derived from the skin are mentioned for further study in Dellmann’s Veterinary Histology?
Ruminant and swine hoof, claw of dogs and cats, chestnut and ergot, horn of ruminants.
In which group of animals are digital pads or footpads present?
Carnivores.
What are digital pads or footpads in carnivores composed of?
Highly cornified, thickened, highly pigmented, and hairless portions of the skin.
What functional adaptations do digital pads or footpads in carnivores have?
They are adapted for locomotion, resist abrasions, and serve as effective shock absorbers.
Which region of carnivore skin contains the thickest epidermis?
The digital pads or footpads.
What specific layers does the thickest epidermis of carnivore footpads include?
All epidermal layers, including the stratum lucidum.
What is the surface texture of the stratum corneum in the digital pads of cats?
Smooth.
What is the surface texture of the stratum corneum in the digital pads of dogs?
Papillated.
What type of tissue makes up the hypodermis of the digital pads in carnivores?
Abundant adipose tissue.
What is the adipose tissue in the hypodermis of digital pads called?
Digital cushion.
What type of gland is present in the digital pads of carnivores?
Coiled tubular sweat glands.
Which part of the body has the thinnest skin?
The scrotum.
How developed is the stratum corneum in the skin of the scrotum?
Not well-developed.
How extensive is the dermis of the scrotal skin?
Not extensive.
What can be said about the abundance and nature of hair follicles in the scrotum?
Hair follicles are not abundant and the hairs are short and fine.
What is the composition of the planum nasale in carnivores?
Thickened and highly cornified epidermis.
What type of glands are absent in the planum nasale of carnivores?
Sebaceous glands and tubular glands.
What species have a planum nasolabiale or planum nasale devoid of hairs?
Ox (planum nasolabiale) and small ruminants like sheep and goats (planum nasale).
What type of glands are found in the planum nasolabiale of the ox and the planum nasale of small ruminants?
Tubular merocrine glands.
What is the function of the tubular merocrine glands in the planum nasolabiale and planum nasale of ruminants?
They moisten the surface.
What are the characteristics of the epidermis in the planum nasolabiale of ox and planum nasale of small ruminants?
Thickened and highly cornified.
What are the characteristics of the planum rostrale in pigs?
Highly cornified and thickened epidermis.
What are small ruminants?
Tubular merocrine glands.
What are the characteristics of the planum rostrale in pigs?
Highly cornified, contains many tubular merocrine glands, and is sparsely covered by fine hairs.
What type of glands are numerous in the planum rostrale of pigs?
Tubular merocrine glands.
How would you describe the hair coverage on the planum rostrale of pigs?
Sparsely covered by fine hairs.
What type of skin structures are found around the nostril of horses?
Hairs and sebaceous glands.
What type of skin surrounds the nostrils in horses?
Thin skin.
What does the external auditory meatus connect?
The pinna and the tympanic membrane.
What types of glands are found in the skin of the external auditory meatus?
Sebaceous glands and ceruminous glands (modified apocrine tubular glands).
What type of hair follicles are present in the skin of the external auditory canal?
Small hair follicles.
What are ceruminous glands, and where are they found?
Modified apocrine tubular glands found in the external auditory canal.
With what structures does the dermis of the external auditory meatus blend?
Perichondrium and periosteum of the supporting cartilage and bone.
What specialized skin structure is located near the eye in sheep?
Infraorbital sinus.
What specialized skin structure is located on the chin of pigs?
Mental organ.
What specialized skin structure is found beneath the chin in cats?
Submental organ.
What are the carpal glands and in which species are they found?
Specialized skin glands found in pigs.
What is the interdigital sinus and in which species is it found?
A specialized skin structure in sheep.
What is the inguinal sinus and which species has it?
A specialized skin structure located in the inguinal region of sheep.
