Integument and Mammals Overview

Subphylum Vertebrata - Mammalia

• Mammals are a subgroup of vertebrates.
• They are introduced in the study.
• Their integument (skin) is discussed in multiple categories.

Integument - General

• The epidermis is the outer layer of skin.
• It is a stratified epithelium made up of multiple layers of cells.
• Keratinocytes, present in the epidermis, produce keratin.
• Stratum corneum is the outermost layer of dead keratinized cells.
• Stratum basale, underneath the stratum corneum, contains undifferentiated cells that generate newer epidermal layers.
• Specialized modifications of the epidermis, such as glands and hair follicles, reside in the dermis.
• Sebaceous glands, sweat glands, hair follicles and nerve endings are present in the dermis

Integument - Hair

• Hair has various functions.
• Insulation is one of its most important functions.
• Hair can indicate or communicate warnings of aggression or fear.
• This is because raised hair is a sign of anger or fear, controlled by the arrector pili muscle.
• It provides tactile information from the environment.
• Nocturnal and burrowing mammals are known to have long hair that aids in sensing the surrounding area.
• It plays a protective role. (e.g. spines of porcupines).
• Hair can also provide camouflage.
• Seasonal changes may result in hair changes in animals (e.g., snowshoe hare, arctic foxes).

Integument - Glands

• Mammals have a wide range of glands in their integument.
• All glands are derivatives of the epidermis.
• They are categorized in four main groups.

1. Sweat Glands

• (i) Eccrine glands: Not connected to hair follicles, active before puberty.
• They secrete a watery fluid, primarily a sodium chloride solution, and play a pivotal role in evaporative cooling.
• They are found in hairless regions like foot pads.
• (ii) Apocrine glands: Connected to hair follicles, become functional in maturity.
• Secretions are viscous fluids and are involved in chemical communication.
• They are found around genitals, armpits.
• Secretions can create odors when interacting with bacteria.

2. Sebaceous Glands

• These glands are found all over the body in association with the hair follicles, including copious quantities in the scalp and face.
• They produce an oily secretion called sebum that lubricates and waterproofs hair and skin.
• Overactive glands can result in acne.

3. Scent Glands

• Modified sebaceous or apocrine glands.
• Secrete pheromones used to communicate or mark territory, warn or intimidate.
• Locations differ greatly depending on the species (e.g., deer, skunks, wolves).

4. Mammary Glands

• Present in all female mammals, and in males in a rudimentary form.
• These glands produce and release milk for nursing offspring in the process of lactation.
• Composed of alveoli (clusters of milk producing glands), which open into ducts.

Integument - Specializations

• True Horns: Keratinized coverings around bone cores, not branched, found in both sexes.
• Antlers: Bone cores covered in vascularized skin (velvet), branched, typically found in males, shed annually. They are used for social display, fighting, and recognition.