20260218-ap1-integument_1

Course Information

  • Course Title: BIO220 A&P 1

  • Instructors: Chirillo

  • Date: Starting from 2026-02-18

  • Support Hours:

    • Tuesday: 11 AM - 12 PM

    • Friday: 1 PM - 2 PM

  • Reminders:

    • Daily reading assignments due before class (up to 4 may be missed without affecting the grade)

    • Quiz 3: Released Monday, due Thursday night

Learning Objectives

  • Functions of the Integumentary System:

    • Describe the various functions performed by the integumentary system.

  • Accessory Structures of Skin:

    • Identify and name the structures associated with the skin.

  • Skin Structure and Layers:

    • Describe and explain the structure and function of each layer of the skin.

  • Skin’s Role in Homeostasis:

    • Explain how the skin helps regulate sensation, temperature, and vitamin D production.

Overview of Skin Structure

  • Components of the Skin:

    • Epidermis

    • Dermis

    • Subcutaneous tissue (hypodermis)

  • Types of Tissue in the Skin:

    • Epidermis:

    • Composed of stratified squamous epithelium

    • Functions: Protection and prevention of water loss

    • Dermis:

    • Composed of connective tissue

    • Provides structural strength (not part of the skin itself)

    • Holds nerves, blood vessels, and accessory structures (glands, hair follicles)

    • Subcutaneous Layer:

    • Loose connective tissue connecting skin to underlying structures

Injection Techniques

  • Injection Types:

    • Intradermal

    • Subcutaneous

    • Intramuscular

  • Consideration for Injection:

    • Angle of needle insertion relative to the skin (e.g. 90° for intramuscular)

Burns Classification

  • Degrees of Burns:

    • First-Degree Burns: Affect the epidermis only (e.g., sunburn).

    • Second-Degree Burns: Affect both epidermis and dermis (blisters).

    • Third-Degree Burns: Full thickness, involving deeper tissues including subcutaneous fat.

Fluid Compartment Overview

  • Fluid Compartments in the Body:

    • Extracellular Fluid (ECF)

    • Intracellular Fluid (ICF)

  • Cell Membrane's Role:

    • Separates intracellular and extracellular fluids, critical for maintaining different chemical environments.

Skin Sensory Receptors

  • **Types of Sensory Receptors: **

    • Free nerve endings (pain receptors)

    • Pacinian corpuscles (pressure receptors)

  • Accessory Structures:

    • Sebaceous glands, sweat glands, hair follicles

    • Arrector pili muscles associated with hair follicles

Epidermis Structure

  • Characteristics of the Epidermis:

    • Avascular (no blood vessels)

    • Receives nutrients through diffusion from dermal capillaries

    • Consists of several layers of epithelial cells

  • Keratinization Process:

    • Involves the stratification of cells, leading to the accumulation of keratin and formation of the skin's protective barrier.

Skin Color and Pigmentation

  • Pigments in Skin:

    • Melanin:

    • Dark pigment produced by melanocytes

    • Provides protection against UV light

    • Deficiency can lead to albinism

    • Carotene:

    • Yellowish pigment located in the epidermis and adipose tissues

  • Blood Flow Influence on Color:

    • Circulating blood can also affect skin color appearance.

Dermis Structure and Function

  • Components of Dermis:

    • Contains connective tissue with collagen and elastic fibers

    • Houses nerves, blood vessels, smooth muscles, and glands

  • Sensory Functions:

    • Responsible for sensations of pain, temperature, and touch

  • Temperature Regulation:

    • Blood vessels in the dermis regulate body heat by changing size to increase or decrease blood flow, consequently affecting heat loss.

Layers of Dermis

  • Types of Dermal Layers:

    • Papillary Layer: Identified by dermal papillae that increase the surface area for exchange

    • Reticular Layer: Composed of dense irregular connective tissue providing strength and elasticity

Mechanism of Temperature Regulation

  1. Blood vessel dilation increases heat loss through the epidermis.

  2. Evaporation of sweat assists in cooling the body.

  3. Blood vessel constriction reduces heat loss.

  4. Reflex actions like blushing involve dilation of dermal blood vessels.

Accessories of Skin

Hair

  • Structure of Hair:

    • Hair shaft and hair follicle

    • Hair root: portion below the skin

    • Components include medulla, cortex, and cuticle

    • Hair color due to the presence of melanin in the hair matrix at the base of the follicle

Glands

  • Types of Glands:

    • Sebaceous Glands: Secrete sebum, maintaining skin moisture and inhibiting bacteria.

    • Sweat Glands:

    • Produce sweat for thermoregulation (hypotonic)

    • Ceruminous Glands: Modified sweat glands found in the ear, producing cerumen (earwax).

    • Mammary Glands: Modified sweat glands responsible for milk production.

Vitamin D Production

  1. Process:

    • Involves 7-dehydrocholesterol, converted under UV light to cholecalciferol.

  2. Pathway:

    • Cholecalciferol travels to the liver, gets modified, and then to the kidneys to form active vitamin D3 (calcitriol).

  3. Function of Active Vitamin D3:

    • Stimulates calcium and phosphate uptake in the intestines, essential for bone health.

Bone Tissue Overview

  • Types of Bone Tissue:

    • Compact Bone: Dense and forms the outer layer of bones.

    • Spongy Bone (Trabecular Bone): Contains spaces that house bone marrow.

Functions of the Skeletal System

  1. Support: Provides structure and shape to the body.

  2. Protection: Protects vital organs (e.g., skull protects the brain).

  3. Movement: Provides leverage for muscle attachment.

  4. Storage: Stores minerals such as calcium and phosphate.

  5. Blood Cell Production: Occurs in bone marrow.

Bone Growth and Remodeling

  • Growth Hormones:

    • Growth hormone, thyroid hormone, and reproductive hormones influence bone growth and closure.

  • Types of Growth:

    • Longitudinal Growth: Increases length of the bone, facilitated by the growth plates (hyaline cartilage).

    • Circumferential Growth: Increases the width of the bone through appositional growth of osteoblasts.

Bone Repair Mechanism

  1. Formation of Hematoma: Blood clot formation at the fracture site

  2. Cartilage Formation: Fibrocartilaginous callus replaces the blood clot

  3. Ossification: The callus is replaced by woven bone, eventually becoming lamellar bone as remodeling occurs.

Calcium Homeostasis

  1. Regulatory Mechanisms:

    • Calcium levels are regulated by parathyroid hormone (PTH) and calcitonin.

  2. PTH Effects:

    • Activates osteoclasts for bone resorption, increasing blood Ca2+.

  3. Calcitonin Role:

    • Inhibits osteoclast activity, decreasing blood Ca2+.

Summary of Key Points

  • The integumentary system covers the body and includes skin and