Integument Microanatomy Pt 2

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Questions and Answers

What is the location of Langerhans cells?

Intra-dermal location (correct)

Epidermal location

Sub-dermal location

Dermal location

What is the origin of Langerhans cells?

Bone marrow monocytes (correct)

Hair follicle cells

Dermal fibroblasts

Epidermal cells

What is unique about compound hair follicles?

They are only found in herbivores

They contain clusters of several hair follicles (correct)

They contain a single hair follicle

They are only found in primates

What is the function of arrector pili muscles?

To contract and cause hair to stand up Signup and view all the answers

What is the primary function of hair?

Insulation, camouflage, social display, sense/protection, and sex recognition Signup and view all the answers

What is the composition of the inner root sheath?

A few layers of squamous cells and a cuticle Signup and view all the answers

What is the function of the dermal papilla?

To carry blood supply to the hair Signup and view all the answers

What is the external root sheath composed of?

A thickened basal lamina Signup and view all the answers

Where are apocrine sweat glands typically located in domestic animals?

Throughout most of the skin Signup and view all the answers

What is the main function of merocrine/eccrine sweat glands in dogs?

Thermoregulation and electrolyte balance Signup and view all the answers

What type of glands empty or need to be manually emptied?

Anal sacs Signup and view all the answers

What is the method of secretion in merocrine glands?

Exocytosis Signup and view all the answers

Where are specialized apocrine glands found in pigs?

Mental organs and planum rostrale Signup and view all the answers

What is the structure of mammary glands?

Tubuloalveolar glands connected by ducts Signup and view all the answers

What is the function of smooth muscle in the teat of mammary glands?

Sphincter function Signup and view all the answers

What is the composition of hooves and claws?

A variation of stratum corneum supported by a highly vascularized dermis Signup and view all the answers

What is the primary function of sebum produced by sebaceous glands?

Antibacterial and waterproofing Signup and view all the answers

Which type of hair follicles lack both apocrine sweat glands and arrector pili muscles?

Secondary hair follicles Signup and view all the answers

What is the function of hair matrix cells?

To constantly divide and produce hair via the help of keratinocytes Signup and view all the answers

What is unique about the structure of whiskers?

They have a blood-filled sinus between the inner and outer dermal root sheath Signup and view all the answers

What is the composition of the cuticle in hair?

A single layer of flat keratinized cells Signup and view all the answers

During which stage of the hair cycle is hair growth most active?

Anagen Signup and view all the answers

What is the mode of secretion of sebaceous glands?

Holocrine secretion Signup and view all the answers

What is the main function of the medulla?

To insulate the hair shaft Signup and view all the answers

Which of the following birds have highly developed uropygial glands?

Ducks Signup and view all the answers

What is the primary difference between primary and secondary hair follicles?

Their size and diameter Signup and view all the answers

What is the primary function of the hair root?

To anchor the hair shaft to the skin Signup and view all the answers

What is the characteristic of epithelial cells in apocrine sweat glands?

Apical secretory caps Signup and view all the answers

What is the primary function of apocrine sweat glands?

Thermoregulation Signup and view all the answers

What is the primary characteristic of the catagen period?

Metabolic activity slows down Signup and view all the answers

What layers of the epidermis are absent in hooves and claws?

Stratum lucidum and stratum granulosum Signup and view all the answers

What is the primary function of the corium in the equine hoof?

To provide a highly vascular and innervated connective tissue Signup and view all the answers

What is the name of the layer that joins the sole with the wall in the equine hoof?

White line Signup and view all the answers

How many primary epidermal laminae are present in the equine hoof?

500-600 Signup and view all the answers

What is the name of the layer that is a continuation of perioplic epidermis?

Stratum externum (tectorium) Signup and view all the answers

What is the composition of the keratinized hoof wall?

Three layers: stratum externum, stratum medium, and stratum internum Signup and view all the answers

How is the keratin arranged within the horn?

Parallel tubules Signup and view all the answers

What is the term for the layer that interdigitates with the primary dermal laminae?

Insensitive laminae Signup and view all the answers

In regards to the anatomy of a hair follicle, what is number 1 referring to?

Cortex Signup and view all the answers

In regards to the anatomy of a hair follicle, what is number 2 referring to?

Medulla Signup and view all the answers

In regards to the anatomy of a hair follicle, what is number 3 referring to?

Glassy membrane Signup and view all the answers

In regards to the anatomy of a hair follicle, what is number 4 referring to?

Dermal papilla Signup and view all the answers

In regards to the anatomy of a hair follicle, what is number 5 referring to?

Hair matrix cells Signup and view all the answers

In regards to the anatomy of a hair follicle, what is number 6 referring to?

Outer root sheath Signup and view all the answers

In regards to the anatomy of a hair follicle, what is number 7 referring to?

Inner root sheath Signup and view all the answers

In regards to the anatomy of a hair follicle, what is number 8 referring to?

Sweat gland Signup and view all the answers

Which stage of the hair cycle is number 1 referring to?

Anagen Signup and view all the answers

Which stage of the hair cycle is number 2 referring to?

Catagen Signup and view all the answers

Which stage of the hair cycle is number 3 referring to?

Telogen Signup and view all the answers

In this image of compound follicles, what is number 1 referring to?

Sweat gland Signup and view all the answers

In this image of compound follicles, what is number 2 referring to?

Primary hair follicle Signup and view all the answers

In this image of compound follicles, what is number 3 referring to?

Sebaceous gland Signup and view all the answers

In this image of compound follicles, what is number 4 referring to?

Secondary hair follicle Signup and view all the answers

What is "A" referring to in this image?

Arrector pili muscle Signup and view all the answers

What does this image depict?

Sinus hairs/whiskers Signup and view all the answers

What does this image depict?

Mammary gland Signup and view all the answers

In this image of an apocrine sweat gland, what does number 1 refer to?

Apical secretory cap Signup and view all the answers

In this image of an apocrine sweat gland, what does number 2 refer to?

Myoepithelial cell Signup and view all the answers

In this image of an equine hoof, what does "A" refer to?

Insensitive laminae Signup and view all the answers

In this image of an equine hoof, what does "B" refer to?

Coronary corium Signup and view all the answers

In this image of an equine hoof, what does "C" refer to?

Laminar corium Signup and view all the answers

What is number 1 referring to?

Stratum medium Signup and view all the answers

What is number 2 referring to?

Stratum internum Signup and view all the answers

In this image of hoof layers, what is number 1 referring to?

Secondary dermal laminae Signup and view all the answers

In this image of hoof layers, what is number 2 referring to?

Primary dermal laminae Signup and view all the answers

In this image of hoof layers, what is number 3 referring to?

Secondary epidermal laminae Signup and view all the answers

In this image of hoof layers, what is number 4 referring to?

Primary epidermal laminae Signup and view all the answers

What is number 6 referring to?

External anal sphincter Signup and view all the answers

What is "B" referring to?

Uropygial/preen gland Signup and view all the answers

What is number 3 referring to?

Tubular horn Signup and view all the answers

What is number 4 referring to?

Intertubular horn Signup and view all the answers

What is number 5 referring to?

Primary dermal laminae Signup and view all the answers

What is number 6 referring to?

Primary epidermal laminae Signup and view all the answers

What is number 7 referring to?

Secondary epidermal laminae Signup and view all the answers

What is number 8 referring to?

Secondary dermal laminae Signup and view all the answers

Study Notes

Langerhans Cells

Langerhans cells are located within the dermis and are derived from bone marrow monocytes.
They are not often seen with H&E staining but can be seen with immunochemistry or electron microscopy.

Epidermal Derivatives

General Info

Epidermal derivatives include hair follicles, compound hair follicles, sinus (tactile) hairs, sebaceous glands, apocrine (sweat) glands, udders and mammary glands, hooves, claws, nails, footpads, anal sacs, and circumanal glands (hepatoid glands).

Compound Follicles

Compound follicles contain clusters of several hair follicles that merge at the level of the sebaceous gland and emerge through one orifice.
They are most common in carnivores.
Compound follicles usually have one primary follicle with an apocrine sweat gland and several secondary hair follicles.

Arrector Pili Muscles

Arrector pili muscles are smooth muscles attached to primary hair follicles that play an insulation role.
Their contraction causes hair to stand up (goosebumps).

Hair

Hair functions include insulation, camouflage, social display, sense/protection, and sex recognition.
Hair is produced by hair follicles.
Hair follicles are invaginations of the epidermis that contain an internal root sheath, external/outer root sheath, dermal papilla, and hair matrix cells.
The inner root sheath is composed of a few layers of squamous cells and a cuticle.
The external/outer root sheath is an external glassy membrane due to the thickened basal lamina, while the external root sheath is continuous with the epidermis.
The dermal papilla is composed of connective tissue that carries blood supply to the hair.
Hair matrix cells are comparable to the stratum basale epidermal layer, as it is the layer of cells that are constantly dividing and producing hair via the help of keratinocytes.
Hair is composed of the medulla, cortex, and cuticle.
The medulla is composed of loose cuboidal cells with areas of air.
The cortex is composed of dense compact keratinized cells.
The cuticle is composed of a single layer of flat keratinized cells.
The hair shaft is located above the skin surface, while the hair root is located within the follicle and ends with a bulb.
The hair cycle involves the following stages: anagen, catagen, and telogen.
During the anagen period, hair bulb cells are mitotically active, meaning that the hair is growing.
The catagen period is the "regressive stage" where metabolic activity slows down and the base of the follicle migrates towards the surface.
The telogen period is the "resting" or "quiescent phase" where hair growth stops, and the base of the bulb is at the level of the sebaceous canal.
New hair grows below the telogen follicle, and the old hair shaft gets shed.
The hair cycle is controlled by daylight, ambient temperature, nutrition, and hormones (estrogen, testosterone, adrenal steroids, and thyroid hormones).

Hair Follicle Types

Hair follicle types include primary and secondary hair follicles.
Primary hair follicles are large in diameter, rooted deep in the dermis, and contain sebaceous glands, arrector pili muscles, and sweat glands.
Examples of primary hair follicles include primary or guard hairs.
Secondary hair follicles are small in diameter, rooted near the surface, may or may not contain sebaceous glands, and lack both apocrine sweat glands and arrector pili muscles.
Examples of secondary hair follicles include secondary or under hairs.

Whiskers

Whiskers are also referred to as "sinus hairs" which are tactile hairs composed of a very large single follicle.
A blood-filled sinus is located between the inner and outer dermal root sheath.
Whiskers contain nerve bundles penetrating the sheath.
Whiskers are attached to skeletal muscle, which allows for voluntary movement.

Sebaceous Glands

Sebaceous glands are located in the dermis, where they produce sebum.
Sebum is a mixture of lipid and cell debris.
Sebaceous glands partake in holocrine secretion, and aid in antibacterial and waterproofing.
Their ducts empty into a follicle.
They can be simple, branched, or compound glands.
Specialized sebaceous glands include:
- Supracaudal glands (in dogs)
- Circumanal/hepatoid glands
- Mental organs/glands (in cats)
- Horn glands (in buck goats)
- Preputial glands (in the smegma of horses)
- Tarsal (meibomian) glands (in eyelids)
- Uropygial glands (preen glands) (in birds)

Apocrine Sweat Glands

Apocrine sweat glands are secreted by apical budding/pinches.
Epithelial cells have apical secretory caps.
Simple coiled tubular glands open into distal hair follicles.
Contractile myoepithelial cells help express product.
In domestic animals, the apocrine sweat gland is located throughout most of the skin, where they function to communicate via attraction or markers.
Specialized apocrine sweat glands can be found in:
- Mammary glands
- Ciliary glands (of Moll) (in eyelid, making tears form)
- Apocrine glands of anal sacs
- Ceruminous glands (ear wax)
- Mental organs and planum rostrale (of pigs)

Merocrine/Eccrine Sweat Glands

Merocrine means that the method of secretion involves excretion via exocytosis.
These glands open directly onto the skin surface rather than the hair follicle.
Merocrine/eccrine sweat glands are minor in domestic animals except for the footpad of dogs, where they aid in thermoregulation and electrolyte balance.
This function is completed via the secreted fluid onto the skin's surface whenever body temperature rises.

Mammary Gland

Mammary glands contain tubuloalveolar glands that are connected by ducts and are separated into lobules by connective tissue septae and interstitium.
Mammary glands are composed of clusters of alveoli forming lobules, and ducts that drain into sinuses.
Mammary glands have smooth muscle in the teat (sphincter).
The height of the epithelium relates to the activity of the gland.

Hooves and Claws

Hooves and claws are skin modifications composed of a variation of stratum corneum, and are supported by a highly vascularized dermis.
Hooves and claws lack stratum granulosum and stratum lucidum.
The equine hoof is their distal phalanx encased in heavily keratinized epidermis (horn).
In the equine hoof, the skin angles internally at the coronary band/groove, causing distal growth of the stratum corneum epidermal layer.
The equine hoof has a white line that joins the sole with the wall.
The corium (dermis) of the equine hoof is a highly vascular and innervated connective tissue (dermis).
The laminar corium-primary dermal laminae (500-600) interdigitates with the primary epidermal laminae.
There is papillae at the coronary corium, sole corium, and distal laminae (terminal papillae).
The epidermis of the equine hoof (insensitive laminae) is avascular.
The dermis in the equine hoof is the coronary corium, and laminar corium.
The keratinized hoof wall has 3 layers: stratum externum (tectorium), stratum medium, and stratum Internum (lamellatum).
Stratum externum (tectorium) is a continuation of perioplic epidermis, referred to as a "glaze".
Stratum medium is composed of the majority of the wall and is produced from the coronary epidermis.
Stratum Internum (lamellatum) is the primary epidermal laminae (~600), and is the insensitive laminae that interdigitates with the primary dermal laminae.
Sensitive laminae is composed of laminar corium with primary dermal laminae.
The horn is composed of keratin arranged into parallel microscopic tubules (like hair shafts) and intertubular horn.

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This quiz covers the characteristics of Langerhans cells and epidermal derivatives, including their location, function, and types.