1.1 Hypodermis and Skin

Integumentary System

The largest organ of mammals that includes skin, hair, glands, and specialized parts.

Hypodermis

The subcutaneous layer, composed of loose connective tissue and fat, providing insulation and padding.

Epidermis

The outermost layer of skin, composed of stratified squamous epithelium.

Dermis

The deeper connective tissue layer of the skin, containing blood vessels, nerves, and hair follicles.

Sebaceous Gland

Glands in the skin that secrete an oily substance to lubricate the skin and hair.

Thermoregulation

The process by which the integumentary system maintains body temperature.

Hair Cycle

The phases of hair growth: anagen (growth), catagen (transition), and telogen (resting).

Papillary Layer

The upper layer of the dermis, rich in blood vessels and cells, and has papillae that increase surface area.

Tactile Hairs

Specialized hairs that are sensitive to touch, aiding in sensory perception.

Feathers

Specialized structures unique to birds, providing insulation, waterproofing, and aiding in flight.

Melanin

A pigment responsible for the color of skin and hair, providing protection against UV radiation.

Keratinization

The process by which skin cells become hardened and waterproof due to the accumulation of keratin.

Vibrissae

Tactile whiskers that serve as sensory structures for animals, often found on the face.

Pterylae and Apteria

Pterylae refer to feather tracts on birds, while apteria are featherless areas between these tracts.

Molt

The process of shedding old feathers and growing new ones, often occurring once a year.

Elastin

A protein in the dermis that provides elasticity and flexibility to the skin.

Collagen

A structural protein in the dermis that provides strength and support to the skin.

Vascularized and Innervated

Refers to the presence of blood vessels and nerve endings in the dermis layer of the skin.

Hypodermis/ Subcutis

Another term for the hypodermis, a layer beneath the dermis composed mainly of adipose tissue.

Meissner's Corpuscle

A type of touch receptor found in the papillary layer of the dermis.

Pacinian Corpuscle

A type of mechanoreceptor that detects deep pressure and vibration in the skin.

Stratum Corneum

The outermost layer of the epidermis, consisting of dead keratinized cells.

Anagen Phase

The active growth phase of the hair cycle.

Catagen Phase

The transitional phase of hair growth where the hair follicle begins to atrophy.

Telogen Phase

The resting phase of the hair cycle during which the hair is shed.

Guard Hairs vs. Undercoat

Guard hairs are longer and stiffer, while the undercoat consists of shorter, softer hairs.

Uropygial Gland

An oil gland located at the base of a bird’s tail that helps keep feathers waterproof.

Tylotrich Hairs

A type of tactile hair found in dogs and cats, associated with touch receptors.

Cornification

The process of keratinization that leads to the formation of a tough, protective outer layer of the skin.