Glands
This germ layer gives rise to the epidermis and its appendages.
ectoderm
This smooth muscle attaches to the follicle.
arrector pili
This division of the conjunctiva lines the eyelid inside surface.
palpebral conjunctiva
On 100× oil immersion you can commonly identify these two organisms on ear cytology.
bacteria and yeast
This membrane separates the external ear from the middle ear.
tympanic membrane
These are modified sebaceous glands located along the eyelid margin.
Meibomian glands
What type of follicle contains a multiple hairs emerging from one follicular opening?
compound follicles (dogs, cats, goats)
Goblet cells contribute to what part of the the tear film.
mucin layer of the tear film
What type of gland is the uropygial gland in birds?
Modified Sebaceous Gland
Modified apocrine glands in the external ear canal form this gland type.
ceruminous glands
How are multicellular exocrine glans of the skin classified?
Duct Structure: Simple (unbranched), compound (branched)
Secretory Unit: Tubular, Acinar, Alveolar
Mechanism of Secretion: Merocrine, Apocrine, Holocrine
Where are follicular stem cells located?
The bulge region
This layer of the tear film provides the lipid component and reduces evaporation.
lipid layer
This type of skin scraping is used to detect burrowing mites, such as Demodex canis or Sarcoptes.
deep skin scraping
What structures are housed in the middle ear vs. the inner ear?
Middle Ear: Ossicles (Malleus, Incus, Stapes) Tympanic membrane, Eustachian tube opening, Tympanic bulla
Inner Ear: Cochlea, Vestibule, Semicircular canal, Cochlear nerve (CN VIII) and vestibular nerve branches
Describe the structure of a sebaceous gland (including it's shape), it's mode of secretion, and what it produces.
Structure: Branched acinar glands, central cluster of sebocytes surrounded by a layer of basal cells
Mode of Secretion: Holocrine
Produces: Sebum
Name the 6 concentric layers of a hair follicle from inner to outer.
Hair shaft: Medulla, Cortex, Cuticle (of hair shaft)
Inner root sheath: Cuticle, Huxley layer, Henle layer
Name the three layers of the tear film from superficial to deep. Which tear film layer is produced by the lacrimal gland and gland of the third eyelid?
lipid, aqueous, and mucin
aqueous layer
Where do melanocytes reside in the hair follicle?
Within matrix cells
Which structure connects the middle ear to the nasopharynx, and what epithelium lines it?
eustachian tube, lined by respiratory epithelium (ciliated pseudostratified columnar)
How are sebaceous glands generally distributed on the skin? Include species specific sebaceous glands.
Sebaceous glands are widely distributed in haired skin as a part of the pilosebaceous unit.
Species differences: Infraorbital, inguinal, and interdigital regions of sheep, base of horns in goats, anal sacs of cats, and prepuce and circumanal regions of dogs all have well developed regions of sebaceous glands. Dog/cat foot pads lack sebaceous glands.
Explain the phases of the hair follicle and name the permanent segments during a normal growth cycle.
Anagen - Active growth, matrix cells proliferate, melanocytes are active, follicle is long and extends deep into dermis/subcutis
Catagen - Short, controlled regression, matrix proliferation stops, lower follicle apoptoses and shrinks upward, melanogenesis stops
Telogen - Follicle is short and inactive
Permanent segments: Infundibulum and isthmus
This is the primary function of the conjunctiva that explains hyperemia (bloodshot) and chemosis (swelling) during inflammation.
vascular and immunological barrier
A dog presents with a pruritic rash. You perform a direct impression smear of a skin lesion, heat-fix it, and stain with a rapid stain. Under 100× oil immersion, you observe clusters of peanut shaped, budding cells. These findings are most consistent with this type of organism.
yeast (Malassezia)
During a tympanic bulla flush in a cat, care must be taken to avoid fluid entering this connected structure, which could lead to aspiration or airway complications. Why is this more of a concern in cats than dogs?
Eustachian tube → nasopharynx
Dogs --> Tympanic bulla is divided by a bony septum into two compartments - limits fluid movement.
Cats --> Tympanic bulla is a single, undivided cavity - Fluid or infection can more easily flow toward the Eustachian tube → aspiration risk is higher.