anatomy and physiology test 1

kms

anatomy

The structure of body parts and their relation to one another

Physiology

the function of each part of the body to sustain life

Gross Anatomy (aka macroscopic anatomy)

Regional – all structures in one part of the body (such as the abdomen or leg)

Systemic – gross anatomy of the body studied by system

Surface – study of internal structures as they relate to the overlying skin

Microscopic Anatomy

Cytology – study of the cell

Histology – study of tissues

Developmental anatomy

Traces structural changes throughout life

Embryology – study of developmental changes of the body before birth

Other specialized branches of anatomy

Pathological anatomy – study of structural changes caused by disease

Radiographic anatomy – study of internal structures visualized by specialized scanning procedures such as X-ray, MRI, and CT scans

Molecular biology – study of anatomical structures at a subcellular level

Topics of Physiology

a. Considers the operation of specific organ systems

i. Renal – kidney function

ii. Neurophysiology – workings of the nervous system

iii. Cardiovascular – operation of the heart and blood vessels

b. Focuses on the functions of the body, often at the cellular or molecular level

c. Understanding physiology also requires a knowledge of physics, which explains

i. electrical currents

ii. blood pressure

iii. the way muscle uses bone for movement

Complementarity of Structure and Function

a. Principle of Complementarity

i. Function always reflects structure

ii. What a structure can do depends on its specific form

Levels of Structural Organization

a. Chemical – atoms combined to form molecules

b. Cellular – cells are made of molecules

c. Tissue – consists of similar types of cells

d. Organ – made up of different types of tissues

e. Organ system – consists of different organs that work closely together

f. Organism – made up of the organ systems

Necessary Life Functions

a. Maintaining boundaries – the internal environment remains distinct from the external environment

b. Movement – locomotion, propulsion (peristalsis), and contractility

c. Responsiveness – ability to sense changes in the environment and respond to them

d. Digestion – breakdown of ingested foodstuffs

e. Metabolism – all the chemical reactions that occur in the body

f. Excretion – removal of wastes from the body

g. Reproduction – cellular and organismal levels

h. Growth – increase in size of a body part or of the organism i. Environmental Factors

i. Nutrients – needed for energy and cell building

ii. Oxygen – necessary for metabolic reactions

iii. Water – provides the necessary environment for chemical reactions

iv. Normal body temperature – necessary for chemical reactions to occur at life-sustaining rates

v. Atmospheric pressure – required for proper breathing and gas exchange in the lungs

Homeostasis

a. Definition

i. ability to maintain a relatively stable internal environment in an ever-changing outside world

ii. The internal environment of the body is in a dynamic state of equilibrium

iii. Chemical, thermal, and neural factors interact to maintain homeostasis

Homeostatic Control Mechanisms

1. Variables produce a change in the body

2. The three interdependent components of control mechanisms:

a. Receptor – monitors the environments and responds to changes (stimuli)

b. Control center – determines the set point at which the variable is maintained

c. Effector – provides the means to respond to stimulus

Negative Feedback

1. In negative feedback systems, the output shuts off the original stimulus

2. Example: Regulation of room temperature

Positive Feedback

1. In positive feedback systems, the output enhances or exaggerates the original stimulus

2. Example: Regulation of blood clotting

Homeostatic Imbalance

i. Disturbance of homeostasis or the body’s normal equilibrium

ii. Overwhelming the usual negative feedback mechanisms allows destructive positive feedback mechanisms to take over

Cell Theory

a. The cell is the basic structural and functional unit of life

b. Organismal activity depends on individual and collective activity of cells

c. Biochemical activities of cells are dictated by subcellular structure

d. Continuity of life has a cellular basis

Plasma Membrane

i. Separates intracellular fluids from extracellular fluids

ii. Plays a dynamic role in cellular activity

iii. Double bilayer of lipids with imbedded, dispersed proteins

iv. Bilayer consists of phospholipids, cholesterol, and glycolipids

1. Glycolipids are lipids with bound carbohydrate

2. Phospholipids have hydrophobic and hydrophilic bipoles

Vesicles

i. Transport of large particles and macromolecules across plasma membranes

1. Exocytosis – moves substance from the cell interior to the extracellular space

2. Endocytosis – enables large particles and macromolecules to enter the cell

3. Transcytosis – moving substances into, across, and then out of a cell

4. Vesicular trafficking – moving substances from one area in the cell to another

5. Phagocytosis – pseudopods engulf solids and bring them into the cell’s interior

Cytoplasm

– material between plasma membrane and the nucleus

Cytosol – largely water with dissolved protein, salts, sugars, and other solutes

Mitochondria

i. Provide most of the cell’s ATP via aerobic cellular respiration

ii. Contain their own DNA and RNA

Ribosomes

i. Granules containing protein and rRNA

ii. Site of protein synthesis

iii. Free ribosomes synthesize soluble proteins

iv. Membrane-bound ribosomes synthesize proteins to be incorporated into membranes

Endoplasmic Reticulum

i. Interconnected tubes and parallel membranes enclosing cisternae

ii. Continuous with the nuclear membrane

iii. Two varieties – rough ER and smooth ER

Rough ER

a. External surface studded with ribosomes

b. Manufactures all secreted proteins

c. Responsible for the synthesis of integral membrane proteins and phospholipids for cell membranes

Smooth ER

a. Tubules arranged in a looping network

b. Catalyzes the following reactions in various organs of the body

i. In the liver – lipid and cholesterol metabolism, breakdown of glycogen and, along with the kidneys, detoxification of drugs

ii. In the testes – synthesis of steroid-based hormones

iii. In the intestinal cells – absorption, synthesis, and transport of fats

iv. In skeletal and cardiac muscle – storage and release of calcium

Golgi Apparatus

i. Stacked and flattened membranous sacs ii. Functions in modification, concentration, and packaging of proteins iii. Transport vessels from the ER fuse with the Golgi apparatus iv. Secretory vesicles leave the Golgi stack and move to designated parts of the cell

Lysosomes

i. Spherical membranous bags containing digestive enzymes ii. Digest ingested bacteria, viruses, and toxins iii. Degrade nonfunctional organelles iv. Breakdown nonuseful tissue v. Breakdown bone to release Ca2+

Peroxisomes

i. Membranous sacs containing oxidases and catalases ii. Detoxify harmful or toxic substances iii. Neutralize dangerous free radicals 1. Free radicals – highly reactive chemicals with unpaired electrons (i.e., O2 – )

Cytoskeleton

i. The “skeleton” of the cell ii. Dynamic, elaborate series of rods running through the cytosol iii. Consists of microtubules, microfilaments, and intermediate filaments

Cilia

i. Whip-like, motile cellular extensions on exposed surfaces of certain cells ii. Move substances in one direction across cell surfaces

Nucleus

i. Contains nuclear envelope, nucleoli, chromatin, and distinct compartments rich in specific protein sets ii. Gene-containing control center of the cell iii. Contains the genetic library with blueprints for nearly all cellular proteins iv. Dictates the kinds and amounts of proteins to be synthesized

Tissues

a. Tissue is a group of cells with similar structure and function b. Four types of tissue i. Epithelial ii. Connective iii. Muscle iv. Nerve

epithelium tissue

Epithelium

a. A sheet of cells that covers a body surface or lines a body cavity

b. Appears in the body as:

covering and lining epithelium

glandular epithelium

c. Forms a boundary between different environments

d. Functions:

protection, filtration, secretion, absorption, exccretion, sensory reception

Special Characteristics of Epithelium

a. Cellularity- composed almost entirely of cells

b. Polarity- apical and basal surfaces

c. Special contacts

i. Tight Juctions

1. impermeable junction that encircles the cell

ii. Desmosomes

1. anchoring junction scattered along the sides of cells

d. Supported by connective tissue- reticular and basal laminae

e. Avascular but innervated

f. Regenerative- replaces lost cells

Classification of Epithelia

a. Simple or Stratified b. Squamous, Cuboidal, or Columnar

Simple Squamous Epithelia

a. Description

i. Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the simplest of the epithelia

b. Function

i. Allows passage of materials by diffusion and filtration in sites where protection is not important; secretes lubricating substances in serosae

c. Location

i. Kidney glomeruli; air sacs of lungs; lining of heart; blood vessels, and lymphatic vessels; lining of ventral body cavity (serosae).

Simple Cuboidal Epithelia

a. Description

i. Single layer of cubelike cells with large, spherical central nuclei

b. Function

i. Secretion and absorption

c. Location

i. Kidney tubules; ducts and secretory portions of small glands; ovary surface

Simple Columnar Epithelia

a. Description

i. Single layer of tall cells with round to oval nuclei; some cells bear cilia; layer may contain mucus-secreting unicellular glands (goblet cells)

b. Function

i. Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action

c. Location

i. Nonciliated type lines most of the digestive tract (stomach to anal canal), gallbladder, and excretory ducts of some glands; ciliated variety lines small bronchi, uterine tubes, and some regions of the uterus

Pseudostratified Columnar Epithelia

a. Description

i. Single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain goblet cells and bear cilia

b. Function

i. Secretion, particularly of mucus; propulsion of mucus by ciliary action

c. Location

i. Nonciliated type in male’s sperm-carrying ducts and ducts of large glands; ciliated variety lines the trachea, most of the upper respiratory tract

Stratified Squamous Epithelia

a. Description

i. Thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous); in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers

b. Function

i. Protects underlying tissues in areas of high abrasion

c. Location

i. Nonkeratinized type forms the moist linings of the esophagus, mouth, and vagina; keratinized type forms the epidermis of the skin, a dry membrane

Stratified Cuboidal Epithelia

a. Rare in the human body, but mostly found in the ducts of some of the larger glands (sweat and mammary glands) b. Typically has two layers of cuboidal cells

Stratified Columnar Epithelia

a. Limited distribution in the body, though there are a small number in the pharynx, male urethra, and lining of some glandular ducts. Often occurs in relation to transitional epithelia. b. Only its apical layer is columnar

Transitional Epithelia

a. Description

i. Resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells dome shaped or squamouslike, depending on the degree of organ stretch

b. Function

i. Stretches readily and permits distension of urinary organ by contained urine

c. Location

i. Lines the ureters, bladder, and part of the urethra

Glandular Epithelia

a. Gland

i. One or more cells that makes and secretes and aqueous fluid

b. Classified by:

i. Site of product release

1. Endocrine

2. Exocrine

ii. Relative number of cells forming the gland

1. Unicellular

2. Multicellular

Endocrine Glands

i. Ductless glands that produce hormones

ii. Secretions include amino acids, proteins, glycoproteins, and steroids

Exocrine Glands

i. More numerous than endocrine glands

ii. Secrete their products onto body surfaces (skin) or into body cavities

iii. Examples include mucous, sweat, oil, and salivary glands

iv. The only important unicellular gland is the goblet cell

v. Multicellular exocrine glands are composed of a duct and secretory unit

Unicellular Exocrine Glands

i. Goblet cells

ii. Found among the intestinal and respiratory tracts among columnar cells

iii. Function:

1. Mucin secretion to produce mucus

Multicellular Exocrine Glands

i. Classified according to:

1. Duct type

a. Simple- unbranched duct

b. Compound- branched duct

2. Structure of their secretory units

a. Tubular- cells form tubes

b. Alveolar or acinar- cells form flasklike sacs

c. Tubuloalveolar - composed of both previous types

Modes of Secretion

1. Merocrine – products are secreted by exocytosis (e.g., pancreas, sweat, and salivary glands)

2. Holocrine – products are secreted by the rupture of gland cells (e.g., sebaceous glands)

Connective Tissue

a. Types of connective tissue i. Connective tissue proper ii. Cartilage iii. Bone iv. Blood

b. Functions of connective tissue i. Binding and support ii. Protection iii. Insulation iv. Transportation

c. Characteristics i. Mesenchyme as their common tissue of origin ii. Varying degrees of vascularity iii. Nonliving extracellular matrix, consisting of ground substance and fibers

Structural Elements of connective tissues

Ground substance

1. unstructured material that fills the space between cells

2. Interstitial (tissue) fluid

3. Adhesion proteins – fibronectin and laminin

4. Proteoglycans – glycosaminoglycans (GAGs)

5. Functions as a molecular sieve through which nutrients diffuse between blood capillaries and cells

ii. Fibers

1. Collagen – tough; provides high tensile strength

2. Elastic – long, thin fibers that allow for stretch

3. Reticular – branched collagenous fibers that form delicate networks

iii. Cells

1. Fibroblasts – connective tissue proper

2. Chondroblasts – cartilage

3. Osteoblasts – bone

4. Hematopoietic stem cells – blood

5. White blood cells, plasma cells, macrophages, and mast cells

Embryonic Connective Tissue

a. Mesenchyme – embryonic connective tissue

i. Gel-like ground substance with fibers and star-shaped mesenchymal cells ii. Gives rise to all other connective tissues iii. Found in the embryo

Areola, loose connective tissue

i. Description

1. Gel-like matrix with all three fiber types; cells: fibroblasts, macrophages, mast cells, and some white blood cells

ii. Function

1. Wraps and cushions organs; its macrophages phagocytize bacteria; plays important role in inflammation; holds and conveys tissue fluid

iii. Location

1. Widely distributed under epithelia of body, e.g., forms lamina propria of mucous membranes; packages organs; surrounds capillaries

Adipose, loose connective tissue

i. Description

1. Matrix as in areolar, but very sparse; closely packed adipocytes, or fat cells, have nucleus pushed to the side by large fat droplet

ii. Function

1. Provides reserve food fuel; insulates against heat loss; supports and protects organs

iii. Location

1. Under skin; around kidneys and eyeballs; within abdomen; in breasts

Reticular, loose connective tissue

i. Description

1. Network of reticular fibers in a typical loose ground substance; reticular cells lie on the network ii. Function

1. Fibers form a soft internal skeleton (stroma) that supports other cell types including white blood cells, mast cells, and macrophages

iii. Location

1. Lymphoid organs (lymph nodes, bone marrow, and spleen)

Dense regular, dense connective tissue

i. Description

1. Primarily parallel collagen fibers; a few elastin fibers; major cell type is the fibroblast

ii. Function

1. Attaches muscles to bones or to muscles; attaches bones to bones; withstands great tensile stress when pulling force is applied in one direction

iii. Location

1. Tendons, most ligaments, aponeuroses

Dense Irregular, dense connective tissue

i. Description

1. Primarily irregularly arranged collagen fibers; some elastic fibers; major cell type is the fibroblast

ii. Function

1. Able to withstand tension exerted in many directions; provides structural strength

iii. Location

1. Dermis of the skin; submucosa of digestive tract; fibrous capsules of organs and of joints

Elastic, dense connective tissue

i. Description

1. Dense regular connective tissue containing a high proportion of elastic fibers

ii. Function

1. Allows recoil of tissue following stretching; maintains pulsatile flow of blood through arteries; aids passive recoil of lungs following inspiration

iii. Location

1. Walls of large arteries; within certain ligaments associated with the vertebral column; within the walls of the bronchial tubes.

Hyaline Cartilage

i. Description

1. Amorphous but firm matrix; collagen fibers form an imperceptible network; chondroblasts produce the matrix and when mature (chondrocytes) lie in lacunae

ii. Function

1. Supports and reinforces; has resilient cushioning properties; resists compressive stress

iii. Location

1. Forms most of the embryonic skeleton; covers the ends of long bones in joint cavities; forms costal cartilages; cartilages of the nose, trachea, and larynx

Elastic Cartilage

i. Description

1. Similar to hyaline cartilage but more elastic fibers in matrix

ii. Function

1. Maintains the shape of a structure while allowing great flexibility

iii. Location

1. Supports the external ear (pinna); epiglottis

Fibrocartilage

i. Description

1. Matrix similar to but less firm than that in hyaline cartilage; thick collagen fibers predominate

ii. Function

1. Tensile strength with the ability to absorb compressive shock

iii. Location

1. Intervertebral discs; pubic symphysis; discs of knee joint

Osseous Tissue (Bone)

a. Description

i. Hard, calcified matrix containing many collagen fibers; osteocytes lie in lacunae. Very well vascularized.

b. Function

i. Bone supports and protects (by enclosing); provides levers for the muscles to act on; stores calcium and other minerals and fat; marrow inside bones in the site for blood cell formation (hematopoiesis).

c. Location

i. Bones

Blood

a. Description

i. Red and White blood cells in a fluid matrix (plasma)

b. Function

i. Transport of respiratory gases, nutrients, wastes and other substances

c. Location

i. Contained within blood vessels

Connective Tissue Type Summary

a. Connective tissue proper

i. Loose connective tissue

1. Areola

2. Adipose

3. Reticular

ii. Dense connective tissue

1. Dense regular

2. Dense irregular

b. Cartilage

i. Hyaline

ii. Elastic

iii. Fibrocartilage

c. Osseous (bone)

d. Blood

Nervous Tissue

a. Introduction

i. Branched neurons with long cellular processes and support cells

ii. Transmits electrical signals from sensory receptors to effectors

iii. Found in the brain, spinal cord, and peripheral nerves

b. Description

i. Neurons are branching cells; cell processes that may be quite long extend from the nucleus-containing cell body; also contributing to nervous tissue are nonirritable supporting cells (not illustrated)

c. Function

i. Transmit electrical signals from sensory receptors and to effectors (muscles and glands) which control their activity

d. Location

i. Brain, spinal cord, nerves

Skeletal Muscle Tissue

i. Description

1. Long, cylindrical, multinucleate cells with obvious striations

ii. Function

1. Initiates and controls voluntary movement; locomotion; manipulation of the environment; facial expression; voluntary control

iii. Location

1. Skeletal muscles that attach to bones or skin

Cardiac Muscle Tissue

i. Description

1. Branching, striated, uninucleate cells interlocking at intercalated discs

ii. Function

1. As it contracts, it propels blood into the circulation; involuntary control

iii. Location

1. Found in the walls of the heart

Smooth Muscle Tissue

i. Description

1. Sheets of spindle-shaped cells with central nuclei that have no striations

ii. Function

1. Propels substances or objects (foodstuffs, urine, a baby) along internal passageways (i.e., peristalsis); involuntary control

iii. Location

1. Found in the walls of hollow organs

Covering and Lining Membranes

i. The body’s membranes incorporate more than one type of tissue

ii. Three types of covering and lining membranes:

1. Cutaneous 2. Mucous 3. Serous

Cutaneous Membrane

i. The skin ii. Consists of a keratinized stratified squamous epithelium (epidermis) connected to a dense layer of dense irregular connective tissue (dermis)

Mucous Membrane

i. Line body cavities that open to the exterior

ii. Digestive, urinary, respiratory tracts

iii. Most contain either stratified squamous or simple columnar epithelia

iv. Deep to the epithelial layer is a layer of connective tissue known as the lamina propria

Serous Membrane

i. Pleural ii. Pericardial iii. Peritoneum

Tissue Trauma

i. Causes inflammation, characterized by:

1. Dilation of blood vessels

2. Increase in vessel permeability

3. Redness, heat, swelling, and pain

ii. Organization and restored blood supply

1. The blood clot is replaced with granulation tissue

iii. Regeneration and fibrosis

1. Surface epithelium regenerates and the scab detaches

The Integumentary System – The Skin

a. aka – The Integument

b. ~7% of an adults total body weight

c. Varies in thickness from 1.5 – 4.0mm

d. The skin and its associated features are referred to as the integumentary system

i. Sweat and oil glands

ii. Hairs

iii. Nails

e. Consists of three major regions:

i. Epidermis – outermost superficial region

ii. Dermis – middle region

iii. Hypodermis (superficial fascia) – deepest region

epidermis

i. Composed of keratinized stratified squamous epithelium, consisting of four distinct cell types and four or five layers

1. Keratinocytes

2. Melanocytes

3. Merkel cells

4. Langerhans’ cells

ii. Outer portion of the skin is exposed to the external environment and functions in protection

Cells of the Epidermis

i. Keratinocytes – produce the fibrous protein keratin

ii. Melanocytes – produce the brown pigment melanin

iii. Langerhans’ cells – epidermal macrophages that help activate the immune system

iv. Merkel cells – function as touch receptors in association with sensory nerve endings

5 Layers of the Epidermis

i. Variation in epidermal thickness determines if skin is thick or thin

ii. From superficial to deep the layers are:

1. Stratum corneum 2

. Stratum lucidum

3. Stratum granulosum

4. Stratum spinosum

5. Stratum basal

Stratum Basale (Basal Layer)

i. Deepest epidermal layer firmly attached to the dermis

ii. Consists of a single row of the youngest keratinocytes

iii. Cells undergo rapid division, hence its alternate name, stratum germinativum

Stratum Spinosum (Prickly Layer)

i. Cells contain a weblike system of intermediate filaments attached to desmosomes

ii. Melanin granules and Langerhans’ cells are abundant in this layer

Stratum Granulosum (Granular Layer)

i. Thin; three to five cell layers in which drastic changes in keratinocyte appearance occurs

ii. Keratohyaline and lamellated granules accumulate in the cells of this layer

Stratum Lucidum (Clear Layer)

i. Thin, transparent band superficial to the stratum granulosum

ii. Consists of a few rows of flat, dead keratinocytes

iii. Present only in thick skin

Stratum Corneum (Horny Layer)

i. Outermost layer of keratinized cells

ii. Accounts for three quarters of the epidermal thickness

iii. Functions include:

1. Waterproofing

2. Protection from abrasion and penetration

3. Rendering the body relatively insensitive to biological, chemical, and physical assaults

Dermis

i. Second major skin region containing strong, flexible connective tissue i

i. Cell types include:

1. Fibroblasts

2. Macrophages

3. Mast cells

4. White blood cells

iii. Composed of two layers

1. papillary

2. reticular

Papillary layer

i. Areolar connective tissue with collagen and elastic fibers

ii. Its superior surface contains peglike projections called dermal papillae

iii. Dermal papillae contain capillary loops, Meissner’s corpuscles, and free nerve endings

Reticular layer

i. Accounts for approximately 80% of the thickness of the skin

ii. Collagen fibers in this layer add strength and resiliency to the skin

iii. Elastin fibers provide stretch-recoil properties

Hypodermis

a. aka – Superficial facia

b. Subcutaneous layer deep to the skin

c. Composed of adipose and areolar connective tissue

d. Anchors the skin loosely to the underlying tissues such as muscle

e. Thickens significantly during weight gain

Melanin

1. Yellow to reddish-brown to black pigment, responsible for dark skin colors

2. Freckles and pigmented moles – result from local accumulations of melanin

3. Only pigment actually produced in the skin

4. Melanocytes are stimulated to increased production of melanin after sun exposure

Carotene

1. Yellow to orange pigment, most obvious in the palms and soles of the feet

2. Accumulates in the stratum corneum and in the hypodermis

3. Color is most obvious where the stratum corneum is the thickest (ie the skin of the heels)

4. Most intense when carotene-rich foods are eaten

hemoglobin

1. reddish pigment responsible for the pinkish hue of the skin

2. Seen in persons with fair skin

3. Oxygenated hemoglobin circulating through the dermal capillaries

4. Caucasian skin has so little melanin, the epidermis is nearly transparent

Sweat Glands (sudoriferous)

a. Different types prevent overheating of the body; secrete cerumen and milk

i. Eccrine sweat glands

1. found in palms, soles of the feet, and forehead

ii. Apocrine sweat glands

1. found in axillary and anogenital areas

iii. Ceruminous glands

1. modified apocrine glands in external ear canal that secrete cerumen

iv. Mammary glands

1. specialized sweat glands that secrete milk

Sebaceous Glands (oil)

a. Simple alveolar glands found all over the body

i. Larger on the face, neck, and upper chest

b. Secrete an oily secretion called sebum

i. Bactericidal action

c. Soften skin when stimulated by hormones

i. Especially androgens, which are most prevalent during puberty

Hair

i. Filamentous strands of dead keratinized cells produced by hair follicles

ii. Contains hard keratin which is tougher and more durable than soft keratin of the skin

iii. Made up of the shaft projecting from the skin, and the root embedded in the skin

iv. Consists of a core called the medulla, a cortex, and an outermost cuticle

v. Pigmented by melanocytes at the base of the hair

Hair Function and Distribution

i. Functions of hair include:

1. Helping to maintain warmth

2. Alerting the body to presence of insects on the skin

3. Guarding the scalp against physical trauma, heat loss, and sunlight

ii. Hair is distributed over the entire skin surface except:

1. Palms, soles, and lips

2. Nipples and portions of the external genitalia

Hair Follicle

i. Root sheath extending from the epidermal surface into the dermis

ii. Deep end is expanded forming a hair bulb

iii. A knot of sensory nerve endings (a root hair plexus) wraps around each hair bulb

iv. Bending a hair stimulates these endings, hence our hairs act as sensitive touch receptors

Types of Hair

i. Vellus – pale, fine body hair found in children and the adult female

ii. Terminal – coarse, long hair of eyebrows, scalp, axillary, and pubic regions

Hair Thinning and Baldness

i. Alopecia – hair thinning in both sexes

ii. True, or frank, baldness

1. Genetically determined and sex-influenced condition

2. Male pattern baldness – caused by follicular response to DHT (dihydrotestosterone)

3. Minoxidil / Finasteride

iii. Alopecia areata

Nails

a. The structure of the nail

i. Scale like modification of the epidermis on the distal, dorsal surface of fingers and toes

Overall Functions of the Integumentary System

a. Protection – chemical, physical, and mechanical barrier

b. Body temperature regulation is accomplished by:

i. Dilation (cooling) and constriction (warming) of dermal vessels

ii. Increasing sweat gland secretions to cool the body

c. Cutaneous sensation – exoreceptors sense touch and pain

d. Metabolic functions – synthesis of vitamin D in dermal blood vessels

e. Blood reservoir – skin blood vessels store up to 5% of the body’s blood volume

f. Excretion – limited amounts of nitrogenous wastes are eliminated from the body in sweat

skin cancer

i. Most skin tumors are benign and do not metastasize

ii. A crucial risk factor for nonmelanoma skin cancers is the disabling of the p53 gene

iii. The three major types of skin cancer are:

1. Basal cell carcinoma

2. Squamous cell carcinoma

3. Melanoma

Basal Cell Carcinoma

i. Least malignant and most common skin cancer

ii. Stratum basale cells proliferate and invade the dermis and hypodermis

iii. Slow growing and do not often metastasize

iv. Can be cured by surgical excision in 99% of the cases

Squamous Cell Carcinoma

i. Arises from keratinocytes of stratum spinosum

ii. Arise most often on scalp, ears, and lower lip

iii. Grows rapidly and metastasizes if not removed

iv. Prognosis is good if treated by radiation therapy or removed surgically