Lecture 2 ch4 Skin ,ch8 Special Senses

Chapter 4: Skin and Body Membranes

Overview

• Essentials of Human Anatomy & Physiology

• Authors: Elaine N. Marieb, Suzanne M. Keller

• Focus: Structure & function of skin and body membranes

Body Membranes

• Two Major Categories:

  • A. Epithelial Membranes

    1. Cutaneous Membranes

       • Definition: Skin, dry membrane, outermost protective layer

       • Structure: Two layers - Epidermis (keratinized stratified squamous epithelium) and Dermis (dense connective tissue)

    2. Serous Membranes

       • Function: Lines body cavities closed to exterior

       • Types:

         • Peritoneum: Abdominal cavity

         • Pleurae: Surrounds lungs

         • Pericardia: Surrounds heart

    3. Mucous Membranes

       • Function: Lines body cavities open to exterior (e.g. digestive, respiratory tracts)

  • B. Connective Tissue Membranes

    • Synovial Membranes

      • Composition: Loose areolar connective tissue

      • Function: Lines fibrous capsules around joints and secretes lubricating fluid

Integumentary System

• Components:

  • Skin (Cutaneous membrane)

  • Skin appendages: Sweat glands, oil glands, hair, nails

• Functions of the Integumentary System:

  • Insulates and cushions deeper body organs

  • Protects from:

    • Mechanical damage (bumps and cuts)

    • Chemical damage (acids, bases)

    • Thermal damage (heat/cold)

    • UV radiation (sunlight)

    • Microbes (bacteria)

    • Water loss

  • Regulates heat loss (controlled by nervous system)

  • Acts as a mini-excretory system (sweat aids in loss of urea, salts, and water)

  • Synthesizes Vitamin D

Structure of the Skin

• Layers of the Skin:

  1. Epidermis

  2. Dermis

  3. Subcutaneous Tissue (Hypodermis)

     • Anchors skin to underlying organs

     • Composed mostly of adipose tissue

     • Functions: Shock absorption, insulation

Epidermis Structure

• Composed of:

  • Stratified squamous epithelium (mostly keratinocytes)

  • Avascular

  • Layers (Strata) from Deepest to Superficial:

    1. Stratum Basale (Germinativum): Deepest layer, mitosis occurs here

    2. Stratum Spinosum: Cells flatten and keratinize

    3. Stratum Granulosum: Contains keratinized cells

    4. Stratum Lucidum: Thick hairless skin only (palms, soles)

    5. Stratum Corneum: Outermost layer, dead cells filled with keratin

Key Epidermal Cells

• Melanocytes: Produce melanin (pigment)

• Epidermal Dendritic Cells: Activate immune response

• Merkel Cells: Sensory touch receptors

Dermis Structure

• Composed of: Connective tissue

• Regions:

  • Papillary Layer (Upper Dermal Region):

    • Contains dermal papillae, capillary loops, and sensory receptors (touch/pain)

  • Reticular Layer (Deepest Skin Layer):

    • Dense connective tissue, blood vessels, sweat/oil glands, deep pressure receptors

Skin Color

• Contributors:

  1. Melanin: Yellow to brown/black pigment

  2. Carotene: Orange-yellow pigment

  3. Hemoglobin: Red coloring from blood in capillaries

Abnormal Skin Colors

• Erythema: Redness due to inflammation or embarrassment

• Pallor: Pale due to emotional stress or anemia

• Jaundice: Yellow indicating liver disorder

• Bruises: Black and blue marks from blood clots under skin

Appendages of the Skin

• Sebaceous (Oil) Glands:

  • Produce sebum; maintains skin moisture and kills bacteria

• Sweat (Sudoriferous) Glands:

  • Two types:

    1. Eccrine Glands: Most numerous, function in temperature regulation

    2. Apocrine Glands: Located in armpit/genitals, begin at puberty

• Hair: Produced by hair follicles, consists of keratinized cells

• Nails: Heavily keratinized modifications, grow from nail matrix

Skin Infections and Allergies

• Common Conditions:

  • Athlete’s foot (fungal infection)

  • Boils and carbuncles (inflammation of hair follicles)

  • Cold sores (herpesvirus)

  • Basal cell carcinoma: Most common skin cancer

  • Malignant melanoma: Most deadly skin cancer

Burns

• Degrees of Burns:

  • 1st Degree (Superficial): Only epidermis damaged, red and swollen

  • 2nd Degree (Superficial Partial-Thickness): Epidermis and part of dermis damaged, red and blistered

  • 3rd Degree (Full-Thickness): Destroys both layers; painless

  • 4th Degree: Extends into deeper tissues; requires surgery and potentially amputation

Rule of Nines

• Used to estimate burn extent; body divided into 11 areas, each ~9% of total body surface area

The Eye: Anatomy and Function

Accessory Structures

• Extrinsic Eye Muscles, Eyelids, Conjunctiva, Lacrimal Apparatus

Conjunctiva

• Lines eyelids and eyeball, secretes mucus for lubrication

Lacrimal Apparatus

• Function: Produces tears, drains into nasal cavity

• Components: Lacrimal gland, ducts, tears contain enzymes that destroy bacteria

Internal Structures of the Eye

• Layers/Tunics of the Eye:

  1. Fibrous Layer: Sclera & cornea

  2. Vascular Layer: Choroid, ciliary body, iris

  3. Sensory Layer: Retina

Lens

• Biconvex, held by suspensory ligaments, divides eye into anterior (aqueous humor) and posterior (vitreous humor) segments

Physiology of Vision

• Visual Pathway: Light is focused on retina, signals travel via optic nerve to visual cortex (occipital lobe)

Common Vision Problems

• Myopia: Nearsightedness

• Hyperopia: Farsightedness

• Astigmatism: Distorted vision due to lens/cornea shape

The Ear: Anatomy and Function

• Divisions: External Ear, Middle Ear, Internal Ear

External Ear

• Components: Auricle, external acoustic meatus

• Function: Collect sound waves

Middle Ear

• Air-filled cavity with ossicles that amplify sound

• Pharyngotympanic Tube: Equalizes pressure for eardrum vibration

Internal Ear

• Contains cochlea (hearing), vestibule, semicircular canals (balance)

Hearing

• Pathway of Sound: Auricle → external canal → tympanic membrane → ossicles → oval window → cochlea → auditory cortex

Equilibrium

• Vestibular Apparatus: Maintains balance through static and dynamic equilibrium

Hearing and Equilibrium Deficits

• Deafness: Can be conductive or sensorineural; Ménière’s syndrome affects balance and hearing

Chemical Senses: Smell and Taste

Smell

• Olfactory receptors located in nasal cavity; stimulated by chemicals in solution

Taste

• Taste buds contain gustatory cells; respond to five basic taste sensations: sweet, sour, bitter, salty, umami