Integumentary System: Feathers, Hair, Glands, and Scales in Birds and Mammals

Feather tracts

Pterylae

Apteric tracts

Featherless areas (apteria)

Melanins

One of the three groups of pigments found in feathers.

Carotenoids

One of the three groups of pigments found in feathers.

Porphyrines

One of the three groups of pigments found in feathers.

Pelage

Fur, hair, or wool found in most mammals.

Hypodermis

Subcutaneous space beneath the skin.

Equine skin

Skin structure in horses, magnified 40x.

Avian skin

Skin structure in birds, magnified 40x.

Feather pulp

The core structure of a feather.

Barbs

Pigmented structures that branch from the feather shaft.

Feather follicle

The skin structure from which a feather grows.

Dermis

The layer of skin beneath the epidermis.

Epidermis

The outermost layer of skin.

Hair

A keratinous strand consisting of a shaft and root.

Guard hairs

Coarse, visible hairs that provide pigmentation.

Undercoat

A denser layer of hair providing insulation.

Hair vs Fur vs Wool

Hair is a basic term; fur is short and dense; wool is from sheep.

Hair density

650,000-2.6 million hairs per square inch.

Exocrine glands

Glands that secrete substances through ducts.

Sebaceous glands

Oily glands that provide waterproofing.

Meibomian glands

Glands that produce oil for the eyelids.

Eccrine glands

Sweat glands not associated with hair follicles.

Apocrine glands

Sweat glands associated with hair follicles, producing viscous sweat.

Meibomian Gland Tumors

Common eyelid abnormalities in dogs, including adenoma or adenocarcinoma.

Schirmer Tear Test

A test to measure tear production in the eyes.

Hipposudoric Acid

A substance produced by hippos, referred to as 'blood sweat'.

Sweatiest Mammals

Mammals with apocrine glands, except humans who also have eccrine glands.

Mammary glands

Glands responsible for producing milk in mammals.

Streak canal

During dry (non-lactating) periods, epidermal lining the streak canal forms a keratin plug that effectively seals off canal.

Mastitis

Clinical significance related to the streak canal.

Anal Glands

Present in all carnivorous mammals, used for scent marking and predator deterrent, and can be subject to blockage or expression.

Domestic Ferret Pre and Post-op Perianal Tumor

Clinical significance related to anal glands.

Apocrine Gland Adenocarcinoma

Clinical significance related to anal glands.

Hooves, Claws, Nails

Keratinized structures at ends of digits.

Hooves

Generally surround distal digit and support body weight.

Nails/Claws

Emerge from dorsal portion and don't support body weight (generally).

West Indian Manatee

Clinical significance related to overgrown hooves.

Corium

Approximately equivalent to dermis.

Onychectomy

Clinical significance related to the corium.

Horns

Keratinized covering with bone core, continued growth, and not branched.

Antlers

Skin viable and is shed, as is bone core, with determinate growth then shed and branched.

True horns

Found in Bovids, can be male or female.

Cervids

Animals with antlers that undergo an annual cycle of growth, velvet phase, and shedding.

Antler Abnormalities

Clinical significance related to antlers, including conditions like 'Antleroma' and Perruque caused by interruption of androgens during velvet phase.

Horn-esque

Rhino 'horns' are keratin, no bone; Giraffe/Okapi have ossicones of ossified cartilage/skin.

Baleen

Plates of keratin grown from gums of upper jaw, built in strainer, referred to as 'whalebone' but not really bone.

Vibrissae

Highly sensory structures prominent in nocturnal species, only found in mammals.

Quills

Modified hairs, with porcupine quills potentially aiding in the development of less painful hypodermic needles.

Adaptations

Examples include Harbor Seals with 'lobes' in skin structure proposed to reduce drag.

Echidnas

Mammals with no teats, known for milk patches.

Male Dayak Fruit Bat

One of the few known occurrences of paternal lactation.

Hairless or Nearly

Refers to cetaceans (only a few guard hairs), elephants, and hippos, which have been artificially selected.

Fish scales

Originate from a bone-like composition layer of the skin and are covered by epidermis.

Reptile scales

Originate from a layer of the skin that contains keratin and may have underlying dermal bone (osteoderms) in some species.

Scutes

Larger scales that give rise to feathers.

Fish slime

Produced by unicellular mucous glands for antimicrobial protection, predator evasion, and osmoregulation.

Amphibian skin

Features cutaneous respiration with capillaries to the epidermis and multi-cellular glands that produce mucous or poison.

Reptile skin

Has fewer skin glands and increasing keratinization, with scales that are epidermal (scutes).

Ecdysis

May be complete or patchy in reptiles.

Skin defects/incision in reptiles

Reptile skin inverts when injured or incised.

Everting suture pattern

Used to close skin defects in reptiles.

Carapace

Formed by the fusion of ribs and the spinal column in turtles and tortoises.

Plastron

Formed by clavicles/interclavicle and gastralia in turtles and tortoises.

Melanin in scutes

Gives pattern to the scutes.

Avian integument

Lacks sweat glands and sebaceous glands, except for one big exception.

Feathers

Grow from feather tracts (Pterylae) and are absent in featherless areas (apteria).

Feather emergence

Involves shedding/grooming of the sheath, receding of the dermal core and artery/vein, and unfurling of the feather.

Broken feathers vs. cut

Differentiates between feather clipping and pinioning.

Evolution of feathers

Described in the Quarterly Review of Biology, detailing the evolutionary origin and diversification of feathers.

Calamus/Quill

The hollow base of a feather that anchors it to the bird's skin.

Shaft/Rachis

The central shaft of the feather that supports the vanes.

Vane

The flat part of the feather that extends from the shaft, consisting of barbs.

Barb

The branches that extend from the shaft of the feather.

Barbule

The smaller branches that extend from the barbs and interlock to form the feather's structure.

Contour Feathers

Feathers that cover the body, aiding in aerodynamics and often overlapping.

Bristles

Specialized contour feathers near the beak.

Down Feathers

Feathers that lack interlocking barbules, resulting in a fluffy texture.

Rictal Bristles

Specialized feathers that provide sensory feedback about wing position.

Flight Feathers

Feathers that are critical for flight, including primaries for thrust and secondaries for lift.

Filoplume

Sensory feathers that help detect the position of other feathers.

Primaries

The flight feathers attached to the manus that provide thrust.

Secondaries

The flight feathers attached to the ulna that provide lift.

Powder Down

Special feathers that never molt and continuously grow, breaking down into a talcum powder-like dust.

Synchronous/Catastrophic Molt

A type of molt observed in some birds where feathers are shed all at once.

Clinical Significance: Arrested Molt

Failure to molt, often observed in captivity due to various factors.

Melatonin Implant

A treatment used for issues related to arrested molt.

Pigmentation

The coloring of feathers due to various pigments such as melanins, carotenoids, and porphyrins.

Structural Color

Color that appears based on the angle and refraction of light, often seen in iridescent feathers.

Uropygial (Preening) Gland

A gland that produces a waxy substance for waterproofing and arranging feathers.

Clinical Significance: Preening Gland Impaction

A condition caused by poor diet, infections, or trauma affecting the preening gland.