Integumentary System of Mammals Overview

Integumentary System of Mammals

• The integumentary system comprises skin, scales, feathers, hair, and glands.
• Mammals have unique body parts with roles in sustenance and adaptation.
• Mammalian body parts crucial to their existence include: hair, skin, skeletal system, teeth, heart, kidneys, and brain.
• Mammals are characterized by hair and mammary glands.
• Other distinctive features include jaw, skeletal, integumentary, and internal anatomy structures.
• Modern mammals belong to three clades: monotremes, marsupials, and eutherians (placental mammals).

Characteristics of Mammals

• Hair is a conspicuous characteristic of mammals.
• Hair functions include insulation for thermoregulation.
• Hair traps air close to the body, retaining heat.
• Hair acts as a sensory mechanism via modified hairs termed vibrisse or whiskers.
• Hair can contribute to protective coloration and social signaling.
• Hair standing on end is an example of social signaling.

Layers of the Skin

• Skin is made up of three layers: epidermis, dermis, and subcutaneous hypodermis.
• Epidermis is the outermost layer; ectodermal in origin; keratinized stratified squamous epithelium; lacks blood vessels, and contains sparse nerve endings for touch and pain.
• Dermis is a connective tissue layer beneath the epidermis; rich in collagen, reticular, and elastic fibers.
• Hypodermis is located beneath the dermis; also called subcutaneous tissue; made of loose connective tissue, adipose tissue, and nerve endings. It connects skin to underlying tissues.

Functions of the Skin

• Thermoregulation: Skin helps regulate body temperature by sweating or heat retention.
• Protects from External factors: A physical barrier protecting organs from many harmful elements.
• Sensation: Detects touch, temperature, pressure, and pain.
• Nutrition: Enables absorption.
• Immunity: Supports immune function.
• Wound Healing: Aids in healing.
• Absorption: Facilitates passage of substances.
• Excretion: Removes waste products.
• Vitamin D production: Skin produces vitamin D when exposed to sunlight.
• 7-dehydrocholesterol becomes previtamin D3 when exposed to sunlight.
• Previtamin D3 rapidly transforms into cholecalciferol (vitamin D3)
• D3 absorbs into blood vessels and transported to tissues and organs.

Cells of the Skin

• Keratinocytes: predominant cells, originate in the basal layer, and form the epidermal barrier.
• Melanocytes: produce melanin, crucial for skin pigmentation.
• Langerhans cells: dendritic cells; part of the immune system; deliver antigens to lymph nodes.
• Merkel cells: sensory cells that are mechanoreceptors for light touch, most prevalent in fingertips.

Appendages of the Skin (Hair, Nails, and Glands)

• Nails (or claws in some mammals): protective coverings on the digits.
• Hair: Insulation, protection from external factors, social signaling.
• Vellus hair, the fine, short hair covering the body of mammals.
• Lanugo, a type of dense, long, fur-like hair found on newborn mammals.
• Mammals have different types of hair (guard hair, vibrissae) that have specialized functions.
• Glands: produce materials for lubrication, various secretions (oils, hormones, water).

Glands of the Skin

• Mammary glands: produce milk
• Sudoriferous glands: sweat glands; eccrine glands produce sweat for thermoregulation; apocrine glands may create secretions.
• Ceruminous glands: produce ear wax
• Sebaceous glands: produce sebum that lubricates hair and skin; provide antibacterial action and anti-inflammatory activity.

Sweat Glands

• Eccrine sweat glands: regulate temperature all over the body, producing mainly water.
• Apocrine sweat glands: found in primates; secrete substances used for chemical communication; not active until puberty.
• Bacteria can break down apocrine secretions; releasing odor.

Sebaceous Glands

• Produce sebum; oily substance.
• Lubricates skin and protects against friction
• Locates in hair follicles.
• Possesses innate antibacterial and anti-inflammatory functions.

Mammary Glands

• Found in mammals
• Produce milk to nourish newborn mammals.
• May be modified sebaceous/eccrine glands.
• Develop only during pregnancy and lactation
• Located in nipples/teats; six pairs in rats.