Integument System Lecture Notes

Flashcards covering the structure, functions, derivatives, and pathologies of the integumentary system based on lecture notes.

Integument

The skin system, including its derivatives; functions as protection, barrier, thermoregulation, sensory, and communication.

Epidermis

The outermost, avascular layer of the skin, composed of stratified squamous epithelium. It gives rise to sweat glands, hair, and sebaceous glands.

Dermis

The middle layer of the skin, composed of dense irregular connective tissue, containing blood vessels, sensory nerves, lymphatics, and arrector pili muscles. It is divided into papillary and reticular layers.

Hypodermis

The deepest layer of the skin, also known as panniculus adiposus and superficial fascia. It is composed of areolar (loose) connective tissue, allowing for movement.

Stratum Corneum

The most superficial layer of the epidermis, consisting of dead cells filled with keratin.

Stratum Lucidum

A clear, poorly-staining layer of 2-3 cells found in the epidermis of thick skin.

Stratum Granulosum

An epidermal layer characterized by tight junctions, keratinocytes producing keratin, and prominent keratohyalin granules.

Stratum Spinosum

An epidermal layer where desmosomes are visible as spindles between cells.

Stratum Basale

The deepest epidermal layer, responsible for mitotic divisions. It contains melanocytes that produce melanin.

Melanocytes

Cells located in the stratum basale that produce melanin, which determines skin and hair color.

Merkel's Disc

A mechanoreceptor located in the basal epidermis and hair follicles, highly sensitive to light touch.

Pacinian Corpuscle

A deep mechanoreceptor in the dermis and hypodermis, sensitive to gross pressure changes and grasping.

Meissner Corpuscle

A mechanoreceptor found in the dermal ridges, responsible for detecting light touch.

Ruffini Ending (Corpuscle)

A mechanoreceptor that responds to skin stretching and finger position.

Cutaneous Trunci (Panniculus Carnosus)

A deep layer of skeletal muscle attached to the fascia of the skin, causing skin twitching and contractions.

Albinism

A genetic condition caused by mutations in genes regulating melanin production, resulting in decreased pigmentation and increased sensitivity to UV light.

Horns

Permanent structures with a hollow bony core (cornual process) extending from the frontal bone, covered by a keratinized sheath (epikeras). Found in both males and females.

Antlers

Non-permanent structures that grow from pedicles on the frontal bone and are shed annually, typically found only in males. They are covered by 'velvet' during growth.

Rhinoceros Horn

Composed of compacted keratin, calcium, and melanin, lacking a bony core, and growing continuously throughout life.

Hair Follicle

A structure derived from the epidermis that produces hair, consisting of a hair bulb, internal and external root sheaths.

Arrector Pili Muscle

A smooth muscle attached to the hair follicle that can straighten or raise hair ('goosebumps').

Feathers

Epidermal derivatives made of keratin, developing from feather follicles in specific tracts, providing thermoregulation, communication, and protection.

Ergot

Raised patches of hardened, hairless skin on the fetlock of horse legs, connected to underlying ligaments, potentially for sensory information.

Chestnut

Raised patches of hardened, hairless skin on the medial side of a horse's leg above the knee (stifle), possibly serving as a tactile or scent gland.

Hooves

Well-developed structures in ungulates, associated with the distal phalanx and composed of an avascular outer epidermal layer and a vascularized inner dermal layer (corium).

Laminae

Folded layers of tissue that connect the hoof wall to the distal phalanx (coffin bone).

Laminitis (Founder)

Inflammation of the laminae of the foot, often affecting front hooves, which can lead to separation of the hoof wall from the distal phalanx and rotation of the coffin bone.

Sweat (Sudoriferous) Glands

Coiled tubular glands that produce a watery fluid containing lactate, urea, Na, K, and proteins, aiding in thermal regulation through evaporative heat loss.

Anhidrosis

A condition characterized by the inability to sweat.

Sebaceous Glands

Branched holocrine glands that produce an oily sebum (fatty acids, cholesterol, glycerol, wax esters), often associated with hair follicles or opening directly to the skin surface.

Sebum

An oily substance produced by sebaceous glands, composed of fatty acids, cholesterol, glycerol, and wax esters.

Marking Glands

Specialized sebaceous glands whose secretions may increase around breeding.

Horn Glands

Specialized sebaceous glands in some animals (e.g., goat) that open directly to the skin surface.