INTEGUMENTARY

HUMAN STRUCTURE & FUNCTION (GCSF 2013)

UNIT 3: INTEGUMENTARY SYSTEM

1. Introduction to the Integumentary System

  • Focus on the structure and function of the integumentary system.

2. Learning Outcomes

  • After the session, students will be able to:

    • Describe the structures of the integumentary system.

    • Explain the functions of the skin:

      • Thermoregulation

      • Protection

      • Sensation

      • Excretion and absorption

      • Synthesis of Vitamin D

3. Structure of the Integumentary System

A. Main Components

  • Skin / Cutaneous Membrane: Comprises three main sections:

    • Epidermis

    • Dermis

    • Hypodermis

B. Accessory Structures

  • Includes:

    • Hair (Pili)

    • Nails

    • Glands (Sebaceous & Sudoriferous)

    • Arrector pili muscle

    • Blood vessels

    • Nerves

4. Skin Anatomy

A. Epidermis

  • Outermost layer, composed of keratinized stratified squamous epithelium.

  • Varies in thickness; thickest at soles and palms.

  • Avascular (no blood vessels) and lacks nerves.

B. Five Types of Cells in the Epidermis

  1. Stem Cells: Develop into keratinocytes, primarily located in the basal stratum.

  2. Keratinocytes: Comprise 90% of the cells, produce keratin and water-resistant lamellar granules.

  3. Melanocytes: 8% of cells, produce melanin for skin color and UV protection.

  4. Langerhans Cells: Immune cells (macrophages) that a affected by UV rays.

  5. Merkel Cells: Tactile epithelial cells that detect touch sensation.

C. Layers of the Epidermis

  • Five Layers:

    1. Stratum Corneum: First/top layer, consists of ≥25 layers of dead cells.

    2. Stratum Lucidum: Second layer, 3-5 layers of dead cells, found in thick skin.

    3. Stratum Granulosum: 2-5 layers of flattened cells where apoptosis occurs.

    4. Stratum Spinosum: 8-10 layers of nucleated cells joined by desmosomes.

    5. Stratum Basale: Single layer of nucleated cuboidal/columnar keratinocytes, site of mitosis.

5. Dermis Structure

A. Components

  • Located between the epidermis and hypodermis, composed of:

    • Loose (areolar) and dense (irregular) connective tissues.

  • Contains blood vessels, nerves, glands, and hair follicles.

B. Layers of the Dermis

  1. Papillary Layer: Superficial, 1/5 of dermis, made of areolar tissue for support.

  2. Reticular Layer: Deep, 4/5 of dermis, dense irregular tissue; provides strength and elasticity.

6. Accessory Structures of the Integumentary System

A. Hair (Pili)

  • Composed of dead keratinized epidermal cells.

  • Sections include hair shaft (above skin) and hair root (penetrates dermis).

  • Follicle contains hair root plexus and blood vessels.

  • Functions: Protection, heat loss reduction, light sensation.

B. Nails

  • Tightly packed, hard, dead keratinized epidermal cells.

  • Consist of:

    • Free edge

    • Nail body (plate)

    • Lunula

    • Root

  • Functions include protection and object manipulation.

C. Glands

  1. Sebaceous (Oil) Glands: Secrete oil to prevent water loss and microbial invasion.

  2. Sudoriferous (Sweat) Glands:

    • Eccrine (Merocrine): Sweats directly to skin surface for cooling.

    • Apocrine: Opens into hair follicles, active after puberty, scented.

  3. Ceruminous Glands: Modified sweat glands in external ear for earwax production; protect from foreign bodies.

7. Functions of the Skin

A. Thermoregulation

  • Regulated by thermoreceptors initiating vasoconstriction/dilation.

  • Sudoriferous glands help cool down the body.

B. Protection

  • Keratin, sebum, and melanin protect against UV rays, microbes, and chemical harm.

C. Sensation

  • Sensory receptors detect touch, pressure, vibration, and pain.

D. Excretion and Absorption

  • Excretes waste via sweat and absorbs certain substances (e.g., medications).

E. Vitamin D Synthesis

  • Initiated in keratinocytes upon sunlight exposure; important for calcium and phosphorus absorption.

F. Self-Identity

  • Unique dermal papillae form fingerprints, assisting in identifying individuals.

8. Revision Points

  1. Explain the functions of skin.

  2. Describe ways of heat loss from the body.

  3. State types of cells in the epidermis layer.

  4. List accessory structures of the integumentary system.

  5. Complete a provided table/diagram.

HUMAN STRUCTURE & FUNCTION - INTEGUMENTARY SYSTEM (GCSF 2013)

  1. Introduction: Overview of structure and function of the integumentary system.

  2. Learning Outcomes:

    • Describe integumentary system structures.

    • Explain skin functions: thermoregulation, protection, sensation, excretion, absorption, and Vitamin D synthesis.

  3. Structure:

    • Components: Skin (epidermis, dermis, hypodermis) and accessory structures (hair, nails, glands, arrector pili muscles, blood vessels, nerves).

  4. Skin Anatomy:

    • Epidermis: Outermost layer, avascular, composed of keratinized stratified squamous epithelium.

    • Cell Types: Stem cells, keratinocytes, melanocytes, Langerhans cells, Merkel cells.

    • Layers: Stratum corneum, lucidum, granulosum, spinosum, basale.

  5. Dermis:

    • Components: Located between epidermis and hypodermis, contains connective tissues, blood vessels, nerves, glands.

    • Layers: Papillary (superficial) and reticular (deep).

  6. Accessory Structures:

    • Hair: Composed of keratinized cells, functions include protection and sensation.

    • Nails: Hardened keratin, protect and aid in manipulation.

    • Glands: Sebaceous glands (oil secretion), sudoriferous glands (sweat), ceruminous glands (earwax).

  7. Skin Functions:

    • Thermoregulation, protection, sensation, excretion and absorption, Vitamin D synthesis, self-identity (fingerprints).

  8. Revision Points: Include explanations of skin functions, heat loss methods, cell types, accessory structures, and completion of diagrams/tables.

HUMAN STRUCTURE & FUNCTION - INTEGUMENTARY SYSTEM (GCSF 2013)

  1. Introduction: Overview of the structure and function of the integumentary system.

  2. Learning Outcomes:

    • Describe the anatomical structures of the integumentary system.

    • Explain the physiological functions of the skin, including thermoregulation, protection, sensation, excretion, absorption, and Vitamin D synthesis.

  3. Structure:

    • Components: The integumentary system is composed of the skin, which includes the epidermis, dermis, and hypodermis, as well as associated structures such as hair, nails, glands, arrector pili muscles, blood vessels, and nerves.

  4. Skin Anatomy:

    • Epidermis: The outermost layer of skin, characterized as avascular (lacking blood vessels) and composed of keratinized stratified squamous epithelium.

    • Cell Types: The epidermis contains several types of cells:

      • Stem Cells: Differentiate into keratinocytes and are primarily found in the basal stratum.

      • Keratinocytes: Make up 90% of the epidermal cells; they produce keratin and water-resistant lamellar granules.

      • Melanocytes: Represent 8% of epidermal cells; they synthesize melanin, contributing to skin color and UV protection.

      • Langerhans Cells: Function as immune cells and can be damaged by UV exposure.

      • Merkel Cells: Act as tactile receptors that detect touch sensations.

    • Layers: The epidermis has five distinct layers:

      • Stratum Corneum: The outermost layer consisting of 25 or more layers of dead cells.

      • Stratum Lucidum: Present only in thick skin, containing 3-5 layers of dead cells.

      • Stratum Granulosum: Comprises 2-5 layers of flattened cells where cell death occurs.

      • Stratum Spinosum: Contains 8-10 layers of nucleated cells interconnected by desmosomes.

      • Stratum Basale: The innermost layer with a single layer of cuboidal or columnar keratinocytes, where mitosis occurs.

  5. Dermis:

    • Components: Located beneath the epidermis and above the hypodermis, the dermis is composed of loose (areolar) and dense (irregular) connective tissues, including numerous blood vessels, nerves, glands, and hair follicles.

    • Layers:

      • Papillary Layer: The superficial portion, comprising about 1/5 of the dermis, made of areolar tissue providing structural support.

      • Reticular Layer: The deeper portion, constituting 4/5 of the dermis, consisting of dense irregular tissue that provides strength and elasticity.

  6. Accessory Structures:

    • Hair: Made from dead, keratinized epidermal cells; includes parts like the hair shaft (above the skin) and hair root (penetrates the dermis), and serves functions such as protection, reducing heat loss, and light sensation.

    • Nails: Composed of tightly packed, hard, dead keratinized cells, functioning primarily to protect the tips of fingers and toes as well as facilitate object manipulation.

    • Glands:

      • Sebaceous Glands: Produce oil (sebum) to lubricate the skin, preventing water loss and microbial invasion.

      • Sudoriferous Glands:

        • Eccrine (Merocrine): Sweat glands that secrete directly onto the skin surface for thermoregulation.

        • Apocrine: Sweat glands that open into hair follicles, activate after puberty, and produce a scent.

      • Ceruminous Glands: Specialized sweat glands in the external ear that produce earwax to protect against foreign bodies.

  7. Skin Functions:

    • Plays a crucial role in thermoregulation, protection against various threats, sensory reception, waste excretion, absorption of specific substances, synthesis of Vitamin D for calcium and phosphorus regulation, and unique self-identity through fingerprints.

  8. Revision Points: For review, include thorough explanations of skin functions, methods of heat loss from the body, types of cells present in the epidermis, identification of accessory structures, and the completion of provided diagrams and tables.