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EXAM 2 Membranes and Integumentary System Flashcards

Bone: General Characteristics

  • Predominantly makes up the skeleton.

  • Composed of a solid matrix.

  • Bone has an excellent blood supply.

  • Osteocytes are located in lacunae within the matrix.

Blood

Structure

  • Composed of 40-45% cells.

  • Extracellular fluid is plasma.

  • Fibrous proteins in the plasma assist with clotting.

Function

  • Main roles include:

    • Transportation of gases (oxygen, carbon dioxide)

    • Nutrients

    • Wastes

    • Hormones

Location

  • Found in the cardiovascular system.

Epithelium

  • Defined by tightly packed cells with limited matrix:

    • Matrix is primarily composed of a basement membrane.

  • Polarity:

    • Apical (top) and basal (bottom) surfaces present.

    • Epithelial tissue does not possess sidedness.

  • Vascularity:

    • Generally avascular (lacks blood vessels).

    • Blood supply varies among different types of epithelial tissues.

Cell Proliferation

  • High in rate, varies among different tissues.

Functions

  • Acts as a lining and barrier, separates inside/outside environments, provides strength and support, and is involved in glandular activity.

Epithelial Membranes as Simplest Organs

  • Composed of two or more types of tissues: epithelial and connective tissue.

  • There are three primary types of membranes:

    • Mucous Membrane:

    • Moist stratified squamous epithelium + areolar connective tissue.

    • Lines digestive, respiratory, urinary, and reproductive tracts.

    • Coated with mucus from mucous glands.

    • Serous Membrane:

    • Simple squamous mesothelium + areolar connective tissue.

    • Analogy: "a fist pushed into a balloon" describes the two-layered structure.

    • Visceral serous membrane: inner layer covering organs.

    • Parietal serous membrane: outer layer covering cavity walls.

    • Secretes serous fluid that fills the cavity between two membranes.

    • Types:

      • Pleura: Surrounds lungs and thoracic cavity.

      • Pericardium: Sac surrounding the heart.

      • Peritoneum: Lines abdominal cavity and organs.

    • Cutaneous Membrane: Skin and its accessory structures.

Functions of Skin

  • Protection:

    • Acts as a physical barrier, is hard and thick.

    • Oil and glycolipid from glands waterproof the skin.

    • Melanin provides protection against UV radiation.

    • Hair adds sensation and physical protection.

    • Chemical Barrier:

    • Maintains acidity (pH) via the acid mantle.

    • RNase enzymes contribute to biological barrier functions, supported by resident immune cells.

  • Body Temperature Regulation:

    • Structures in integumentary system controlled by the autonomic nervous system.

    • Heat loss mechanisms include sweating (evaporative cooling) and vasodilation.

    • Heat retention methods include reduced sweating and vasoconstriction.

  • Cutaneous Sensation:

    • Contains sensory neuron endings in the epidermis and dermis.

    • Detects temperature, pressure, and pain through receptors in the dermis and hair follicles.

  • Vitamin D Synthesis:

    • Cholesterol is converted to Vitamin D via UV light exposure.

    • Necessary for calcium absorption from the gut.

  • Blood Reservoir:

    • Highly vascularized.

    • Skin capillary beds close when blood is needed elsewhere.

  • Excretion:

    • Eliminates nitrogenous wastes and byproducts of amino acid metabolism.

    • Water loss is managed through skin operations.

Skin Histology: General Structure

  • Epidermis:

    • Composed of keratinized stratified squamous epithelium.

    • Cell Types:

    • Keratinocytes:

      • Produce keratin (soft and protective).

      • Form desmosome connections for structural integrity and waterproofing properties.

      • Produced in the basal layer and keratinize as they migrate to the surface.

      • Typical turnover time is 52-75 days.

    • Melanocytes:

      • Produce melanin, the pigment responsible for skin tone and protection against UV light.

      • Similar numbers of melanocytes exist across skin tones, but activity levels vary; darker skin has more active melanocytes leading to increased pigment production.

    • Merkel Cells:

      • Sensory cells located at the dermal-epidermal junction.

    • Immune Cells:

      • Including phagocytic cells that respond to infection.

  • Dermis:

    • Composed of connective tissue.

    • Mainly consists of fibroblasts that secrete collagen and ground substances (gel-like).

    • Provides structural support and contains blood vessels and nerve endings.

    • Layers:

    • Papillary Layer:

      • Loose areolar connective tissue.

      • Contains dermal papillae that interdigitate with epidermal ridges (key in fingerprint formation).

    • Reticular Layer:

      • Dense irregular connective tissue, which consists of thick bundles of collagen fibers.

  • Hypodermis (Subcutaneous Tissue):

    • Composed of loose connective tissue and adipose tissue.

Location and Characteristics of Skin Types

  • Thick Skin:

    • Located on palms, fingertips, soles of feet.

    • Has an additional stratum (epidermal ridges).

  • Thin Skin:

    • Found everywhere else on the body.

    • Characterized by shallower epidermal ridges, hair follicles present.

Appendages of Skin

Hair

  • Comprised of dead, keratinized cells.

  • Hair shaft is the visible part; cells are added at the base of the hair root.

  • Hard keratin determines texture based on shaft shape in cross-section:

    • Flat/ribbon-like produces tight curls.

    • Oval leads to wavy hair.

    • Round results in straight, coarse hair.

  • Anatomy of Hair Follicles:

    • Hair bulb is the epithelial growth zone containing melanocytes and keratinocytes.

    • Papilla nourishes hair matrix responsible for hair growth.

  • Hair Distribution:

    • Vellus Hair: Soft, fine hair, predominantly unpigmented pre-puberty.

    • Terminal Hair: Coarse, longer, and pigmented; localized growth patterns.

  • Growth Cycles:

    • Includes a growth phase, resting phase, shedding, and new growth begins.

Nails

  • Composed of dead, keratinized cells.

  • Main components include: nail, nail root, nail body, free edge, and nail matrix (found at the nail root and responsible for nail growth).

Sebaceous Gland

  • Produces sebum, which is oily and rich in lipids.

  • Functions to waterproof, soften, and lubricate the skin with antibacterial properties.

  • Distribution includes the body except for thick skin, concentrated on the face, neck, and upper chest.

Sweat Glands

  • Eccrine Sweat Gland:

    • Most common type with a watery secretion made up of 99% water, salts, and trace metabolic wastes.

    • Functions in temperature regulation.

    • Located in the dermis, with ducts opening to the skin surface, independent of hair follicles.

  • Apocrine Sweat Gland:

    • Larger and associated with hair follicles.

    • Secretes sweat combined with proteins and lipids for bacterial protection; odor results from bacterial degradation.

    • Mainly located in the axillary (armpit) and genital regions.

  • Ceruminous Gland:

    • Modified apocrine gland producing earwax.

  • Mammary Gland:

    • Modified apocrine gland that produces milk.

Skin Pathologies

Skin Cancer

  • Basal Cell Carcinoma:

    • Most common type, originates in the deepest layer (basal layer).

    • Least malignant with a 99% cure rate; rarely metastasizes.

  • Squamous Cell Carcinoma:

    • Originates in the middle layers of the epidermis.

    • Rapid growth and spread; good cure rate if detected early.

  • Malignant Melanoma:

    • Represents 5% of skin cancers, resulting from mutations in melanocytes.

    • Often originates from pre-existing moles; fast-spreading and potentially fatal if not caught early.

Burns

  • Overview:

    • Lead to protein denaturation, cell death, and dehydration throughout the body.

  • Causes include heat/fire, UV radiation, chemicals, and electricity.

  • Classification:

    • First-Degree Burn:

    • Affects the epidermis with redness, swelling, and pain; heals in a few days.

    • Second-Degree Burn:

    • Involves both the epidermis and dermis; results in blisters with prior symptoms; healing time depends on the depth of dermal damage.

    • Third-Degree Burn:

    • Complete destruction of epidermis and dermis, deeper tissues are also impacted; typically no pain (nerve endings destroyed); surgical skin grafts are often required.

Aging of the Skin

  • Aging leads to dehydration and increased vulnerability to infections.

  • Greater caloric demand for tissue repair; accelerated aging caused by sun exposure and smoking.

  • Loss of collagen and elastin; reduced number of all dermal layers, leading to decreased blood flow and impaired temperature regulation.

  • Thinner skin that becomes more fragile over time due to decreased epidermal layers and dermal thickness, as well as reduced sebaceous and sweat gland activity.

  • Increased melanocytes may lead to the formation of age spots and potential for melanoma development.