integumentary

Overview of the Integumentary System

  • The integumentary system covers the entire outer surface of the body and performs various functions.

Functions of the Integumentary System

  • Functions Include:

    • (A) Protection

    • (B) Communication

    • (C) Thermoregulation

    • (D) Molecule Production and Storage

    • (E) Waste Removal

    • (F) All of these are functions of the integumentary system.

Structure of the Integumentary System

  • The integument has three distinct layers:

    • Epidermis

    • Dermis

    • Hypodermis

Illustrated Components of the Skin

  • Components Include:

    • Hair shaft

    • Sweat gland pore

    • Sweat

    • Stratum corneum

    • Stratum basale

    • Capillary

    • Dermal papilla

    • Basement membrane

    • Tactile (Meissner's) corpuscle

    • Sebaceous gland

    • Arrector pili muscle

    • Sweat gland duct

    • Lamellated (Pacinian) corpuscle

    • Hair follicle

    • Sweat gland

    • Nerve cell process

    • Adipose tissue

    • Blood vessels

    • Muscle layer

Epidermis

  • Description:

    • The outer layer of the skin.

    • Derived from ectoderm and consists of stratified squamous epithelium.

Cellular Structure and Functions

  • Cells divide mitotically in the stratum germinativum (basale).

  • As cells migrate outward, they undergo keratinization and die, forming the keratinized stratum corneum.

  • Increased keratin production leads to the formation of a callus in high-traffic areas.

Skin Pigmentation

  • Melanocytes are specialized cells that produce melanin, a dark pigment.

  • Melanin is transferred to keratinized cells and becomes concentrated on the outward-facing side of the cell.

Melanin Functions

  • Melanin plays a crucial role in protecting DNA from ultraviolet (UV) light damage.

  • Increased UV exposure stimulates greater melanin production to enhance protection.

Nails

  • Nails are also derived from epidermal tissue.

  • Development Process:

    • Epithelial cells grow and divide from the nail bed.

    • They produce a harder form of keratin, forming a dense layer of thin cells for added strength.

Dermis and Hypodermis

  • Composition: Both layers are mesodermal in origin.

  • The dermis consists of collagen and elastin, providing toughness and elasticity to the skin.

  • The hypodermis contains adipose tissue and loose connective tissue, providing insulation and attaching the skin to deeper musculature.

Functions of the Dermis

  • The dermis supports epidermal nutrients via blood vessels.

  • Nerve cells within the dermis enable signal reception and transmission from the skin.

  • The dermis plays essential roles in thermoregulation through hair follicles and sweat glands.

Tissue Components in the Dermis

  • The dermis includes:

    • Adipocytes (fat cells)

    • Blood and lymphatic vessels

    • Muscles

    • Glands

    • Hair follicles

    • Sensory receptors

    • Examples:

    • Arrector pili muscles

    • Sebaceous (oil) glands

    • Pacinian corpuscles

Sensory Receptors Related to Touch

  • Free Nerve Endings:

    • Wrap around hair follicles, forming a nerve plexus that triggers receptors when hair is moved.

    • Respond to extremely light touch and undergo rapid adaptation.

  • Shallow Touch Receptors:

    • Meissner’s Corpuscles:

    • Located in the outer dermis, responsive to light pressure, adapt rapidly.

    • Merkel’s Discs:

    • Sensitive to light steady pressure, concentrated in fingertips, adapt slowly.

  • Deeper Touch Receptors:

    • Pacinian Corpuscles:

    • Found in dermis and joints, respond to vibration and deep pressure.

    • Ruffini Endings:

    • Respond to stretch and sustained pressure, located in the dermis and joints.

Hair Structure and Function

  • Hair is derived from the epidermis through the development of hair follicles.

  • Follicles grow downwards and associate with dermal papillae for vascularization.

  • The base of the hair follicle forms a bulb and hair root.

Layers of Hair

  • Inner Medulla:

    • Hollow and filled with air.

  • Middle Cortex:

    • Contains tightly packed cells, site of pigment granules released by melanophores.

  • Outer Cuticle:

    • Scale-like layer that covers the hair.

Pigmentation of Hair

  • Hair color results from the quantity of two t. ypes of melanin:

    • Pheomelanin: Produces shades from blonde to red.

    • Eumelanin: Produces brown and black shades.

Sebaceous Glands

  • Functions of sebaceous glands include:

    • (A) Increase insulation

    • (B) Release heat from the body

    • (C) Perceive temperature

    • (D) Perceive movement and light pressure

    • (E) Keep hair soft and pliant.

Sweat Glands

  • Glands have multiple roles:

    • Eccrine Sweat Glands:

    • Release fluid, excrete water, and waste in response to increased temperature.

    • Blocked pores may lead to acne formation.

    • Apocrine Sweat Glands:

    • Found in the axial and inguinal regions, produce a thicker and viscous sweat that is broken down by bacteria.

Modified Sweat Glands

  • Ceruminous Glands:

    • Produce earwax and empty into the external ear canal.

  • Mammary Glands:

    • Produce milk, empties out through the nipple.

Tissue Recovery in the Integumentary System

  • In response to skin breaks:

    • The hypodermis releases clotting factors, leading to blood clot formation and scab development.

    • Fibroblasts: Produce collagen fibers to close the wound.

    • Epithelial Cells: Start to grow and divide to fill the gap left by injury.

    • White Blood Cells: Clear out dead and damaged cells.

  • After the scab sloughs off, a scar may remain due to extensive collagen fiber production during the healing process.