Exam 4 Review
Respiratory System
General function is to obtain oxygen for use by body cells and eliminate carbon dioxide that body cells produce
Two processes
Internal respiration – cellular respiration, metabolic processes carried out within mitochondria, derive energy from nutrient molecule,
use O2, produce CO2
External respiration – exchange of O2 and CO2 between external environment and body cells, four steps
1.
2.
3.
4.
Ventilation – movement of air into and out of lungs
O2 and CO2 exchanged between air in alveoli and blood in pulmonary capillaries by diffusion
Blood transports O2 and CO2 between lungs and tissue
O2 and Co2 exchanged between tissue and blood by diffusion across systemic (tissue) capillaries
Nonrespiratory Functions
1.
Route for water loss and heat elimination
2.
Enhances venous return
3.
Helps maintain normal acid-base balance
4.
Enables speech, singing, and other vocalizations
5.
Defends against inhaled foreign matter
6.
Removes, modifies, activates, or inactivates various materials passing through the pulmonary circulation
7.
Nose serves as the organ of smell
Airways
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Nasal passage – nose
Pharynx – common for breathing and eating
Larynx – voice box
Trachea – windpipe, rigid nonmuscular tube, rings of cartilage prevent collapse
Right and left bronchi, same as trachea
Bronchioles – alveoli are air sacs that cluster at ends of terminal bronchioles, no cartilage to hold open, smooth muscle
innervated by ANS, sensitive to chemical hormones
o Alveoli – thin walled, inflatable sacs, gas exchange, encircled by capillaries
 Type I alveolar cell – make up single layer of wall, flattened
 Type II alveolar cell – secrete pulmonary surfactant
 Alveolar macrophages guard lumen
 Pores of Kohn – permit airflow between adjacent alveoli
Lungs
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Occupy most of thoracic cavity – share with vessels, esophagus, thymus, nerves
Two lungs divided into several lobes, elastic connective tissue
Thorax – formed by 12 pairs of ribs, connect to sternum anteriorly and thoracic vertebrae posteriorly
Diaphragm – dome shaped sheet of skeletal muscle, separate thoracic from abdominal
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Pleural sac – double walled closed sac separating each lung from thoracic wall
o Pleural cavity – interior of pleural sac
o Intrapleural fluid – secreted by pleura, lubricates
Respiratory Mechanics
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Pressure
o Atmospheric (barometric) – 760 mm Hg
o Intra-alveolar (intrapulmonary) – pressure within alveoli, 760 mm Hg but changing
 Less than atmospheric = air enters lungs
 More than atmospheric = air exits lungs
 Boyle’s Law – at constant temp, pressure is inverse of volume
o Intra-pleural (intrathoracic) – pressure within pleural sac – 756 mm Hg
Inspiration
o Muscles
 Diaphragm – innervated by phrenic nerve, 75% of enlargement of thoracic cavity during quiet respiration is
due to contraction/flattened of this muscle
 Expansion decreases intra-pleural pressure to 756 mm Hg, lungs are drawn in, intra-pleural pressure
decreased to below atmospheric, air enter lungs
 External intercostals muscles – innervated by intercostal nerves
 Accessory muscles
 Sternocleidomastoid
 Scalenus
Expiration
o Begins with the relaxation of inspiratory muscles
 Size of thoracic cavity decreases, intra-pleural pressure increases, intra-alveolar pressure increases to level
about atmospheric, air exits lungs
o Forced expiration – contraction of expiratory muscles
 Abdominal wall muscles
 Internal intercostals muscles
Airway Resistance
o Primary determinant is radius of conducting airway
o ANS controls contraction of smooth muscle in bronchiole walls
o COPD abnormally increases airway resistance where expiration is more difficult than inspiration
 Chronic bronchitis
 Asthma
 Emphysema
Compliance – how much effort is required to stretch/distend lungs
o Elastic recoil – how readily lungs rebound after stretching
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Depends on two factors
 Elastic connective tissue in the lungs
 Alveolar surface tension – surfactant lines each alveolus, reduces tendency of alveoli to recoil, helps
maintain stability (newborn respiratory distress syndrome)
o Decreased by factors such as pulmonary fibrosis
Work of Breathing
o Usually requires 3% of total energy expenditure
o Lungs normally operate at half full
o Increased when
 Pulmonary compliance is decreased
 Airway resistance is increased
 Elastic recoil is decreased
 Need for increased ventilation
Lung volume/capacity measured by spirometer shown on a spirogram, graph that records expiration/inspiration
Tidal Volume (TV)
Inspiratory Reserve Volume (IRV)
Inspiratory Capacity (IC)
Residual Volume (RV)
Functional Residual Capacity (FRC)
Vital Capacity (VC)
Total Lung Capacity
Forced Expiratory Volume-1s (FEV1)
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Description
Volume of air entering/leaving in a single breath
Extra volume that can inspired above TV
IRV+IC
Air remaining in lungs after maximal expiration
ERV+RV
Maximum volume that can be expired after maximal inspiration
Maximal volume the longs can hold
Volume of air during 1st second of VC determination
Average Value
500 mL
3000 mL
3500 mL
1200 mL
2200 mL
4500 mL
5700 mL
Respiratory Dysfunction
o Obstructive lung disease – more difficulty emptying lungs than filling, TLC is the same but FRC and RV are elevated
because air is trapped in lungs following inspiration, reduced VC and FEV1
o Restrictive lung disease – lungs are less compliant than normal, TLC, IC and VC are reduced because lungs cannot
expand, RV and FEV1 usually normal because airways are not blocked
o Other
 Affecting diffusion of O2 and CO2 across pulmonary membranes
 Reduced ventilation due to mechanical failure
 Failure of adequate pulmonary blood flow
 Ventilation/perfusion abnormalities – poor matching of blood and air so efficient gas exchange cannot occur
Pulmonary ventilation (mL/min) = tidal volume (mL/breath) x respiratory rate (breaths/min)
Alveolar ventilation = (tidal volume-dead space) x respiratory rate
o More important than pulmonary
o
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Volume of air exchanged between the atmosphere and alveoli per minute
Less than pulmonary ventilation due to anatomic dead space – volume of air in conducting airways that is useless for
exchange (~150 mL)
Dead space - of little importance in healthy people but can increase to lethal level in disease
Local controls act on smooth muscle or airways and arterioles to match airflow and blood flow
CO2 in alveoli high  decreased airway resistance, increases airflow
O2 in alveoli high  pulmonary vasodilation, increases blood flow
o
Gas exchange
o Dalton’s Law of Partial Pressure – total pressure exerted by a mixture is the sum of all partial pressures
o Henry’s Law of Mixture of Gases – when a mixture of gases is in contact with a liquid, each gas will dissolve in
proportion to its partial pressure
o Atmospheric air is 79% nitrogen and 21% oxygen
Gas Transport
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Most oxygen is transported in the blood bound to hemoglobin (98.5%)
o Hemoglobin + oxygen = oxyhemoglobin, reversible, favored toward product
o This combination tends to occur as oxygen diffuses from alveoli to pulmonary capillaries
o A small percentage of oxygen is dissolved in blood plasma
o Dissociation occurs in tissue cells, favored when oxygen leaves systemic capillaries and enters tissue
o Partial pressure of oxygen determines hemoglobin saturation
 Saturation is high when partial pressure is high – lungs
 Saturation is low when partial pressure is low – tissue
 Shown in the Oxygen Hemoglobin Dissociation Curve
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Most carbon dioxide is found as bicarbonate (60%) or bound to hemoglobin (30%)
o Carbon dioxide combines with water in the presence of carbonic anhydrase (in erythrocytes) to form carbonic acid 
hydrogen ion + bicarbonate ion, favored in tissue cells
o The reverse in favored in lungs
o Chloride Shift – plasma membrane of RBC passively allows for diffusion of bicarbonate and chloride ions
o Haldane Effect – removal of oxygen from hemoglobin at tissues allows hemoglobin to bind to carbon dioxide
o
There is net diffusion of oxygen to blood until hemoglobin is maximally saturated (97.5% of 100 mm Hg)
Increased release of carbon dioxide from tissue increases hemoglobin dissociation from oxygen shifting curve to the right –
Bohr Effect
o Increased acidity, high temperature and production of BPG also shifts curve to the right
Hemoglobin has a higher affinity for carbon monoxide than oxygen
Abnormalities
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6.
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9.
Hypoxia – having insufficient O2 at the cellular level
a. Hypoxic hypoxia
b. Anemic hypoxia
c. Circulatory hypoxia
d. Histotoxic hypoxia
Hyperoxia – having above-normal PO2, only occurs when breathing supplemental O2, dangerous
Hypercapnia – excess CO2 in blood, caused by hypoventilation
Hypocapnia – below-normal PCO2 level, cause by hyperventilation
a. Anxiety
b. Fever
c. Aspirin poisoning
Apnea – cessation of breathing
Asphyxia – oxygen starvation in the tissues
Cyanosis – lack of oxygen in blood causing blueness of skin
Dyspnea – difficult breathing
Eupnea – normal breathing
Control of Respiration
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Medullary respiratory center
o Dorsal respiratory group – inspiratory neurons
o Ventral respiratory group – inspiratory and expiratory neurons
Pre-Botzinger complex – believed to generate respiratory rhythm
Pons respiratory centers
o Pneumotaxic center – sends messages to DRG to turn off inspiratory neurons, dominates apneustic center
o Apneustic center – prevents inspiratory neurons from switching off, provides boost to inspiratory drive
Hering-Breur reflex – prevent over-inflation of lungs
Chemical factors – determine magnitude of ventilation (PCO2, PO2, H+)
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Peripheral chemoreceptors
 Carotid bodies in carotid sinus
 Aortic bodies in aortic arch
Factors that increase ventilation during exercise
o Reflexes from body movement
o Increase in body temperature
o Epinephrine release
o Impulses from cerebral cortex
Factors that increase ventilation BUT not related to need for Gas Exchange
o Protective reflex like sneezing, coughing
o Inhalation of noxious agents  immediate cessation of breathing
o Pain stimulating respiratory center
o Emotion states
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ROME
Inhibition occurs during swallowing
Respiratory= Opposite: pH is high, PCO2 is down (Alkalosis) pH is low, PCO2 is up (Acidosis)
Metabolic = Equal: pH is high, HCO3 is high (Alkalosis) pH is low, HCO3 is low (Acidosis)
Digestive System
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Primary function – transfer of nutrient, water and electrolytes from ingested food into body’s internal environment
Functions
o Motility
 Muscular contractions that mix and move forward the contents in digestive tract
 Two types of motility
 Propulsive movement – push contents forward
 Mixing movement
o Mix food with digestive juice promoting digestion
o Facilitates absorption by exposing all parts of contents to absorbing surfaces
o Secretion
 Consist of water, electrolytes and specific organic constituents
 Released into lumen when neural or hormonal signal given
 Normally reabsorbed into blood after participation
o Digestion
 Biochemical breakdown of complex food into smaller, absorbable units
 Carbohydrates  monosaccharides
 Proteins  amino acids
 Fats  glycerol and fatty acids
 Enzymatic hydrolysis
o Absorption
 Small units resulting from digestion are transferred with water, vitamins and electrolytes from digestive
lumen to blood or lymph
Pathways
o Mouth  pharynx  esophagus  stomach  small intestine (duodenum, jejunum, ileum)  large intestine
(cecum, appendix, colon, rectum)  anus
Accessory digestive organs
o Salivary glands
o Exocrine pancreas
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Biliary system
 Liver
 Gallbladder
Digestive Tract – same structure everyone in pathway
o Four major tissue layers
 Mucosa (innermost)
 Lines luminal surface, is highly folded increasing surface area
 Three layers
o Mucous membrane – protective surface, modified for secretion and absorption,
contains
 Exocrine gland cells – secrete digestive juices
 Endocrine gland cells – secrete blood-borne GI hormones
 Epithelial cells – absorbing digestive nutrients
o Lamina propia – houses Gut-Associated Lymphoid Tissue (GALT), defense against
disease-causing bacteria
o Muscularis mucosa – smooth muscle
 Submucosa
 Thick layer of connective tissue providing distensibility/elasticity
 Has large blood and lymph vessels
 Has nerve network known as submucosal plexus
 Muscularis externa
 Major smooth muscle coat of digestive tube
 Two layers
o Circular layer – inner, contraction decreases diameter
o Longitudinal layer – outer, contraction shortens
 Produces propulsion and mixing
 Myenteric plexus lies between two layers
 Serosa (outermost)
 Secretes serous fluid to provide lubrication between digestive organs and viscera
 Continuous with mesentery providing fixation and support while mixing/propulsing
Regulation
o Autonomic smooth muscle
o Intrinsic nerve plexus
o Extrinsic nerves
o GI hormones
Oral Cavity
o Lips – forms opening, procure/guide/contain food, speech, well-developed tactile sensation
o Palate – forms roof of oral cavity (separate mouth and nasal passage)
 Uvula – seals off nasal passage when swallowing
o Tongue – forms floor of oral cavity, made of skeletal muscle, chewing/swallowing, speech, taste buds
o Pharynx – cavity at rear of throat, common for respiration and digestion
 Tonsils – within sides, lymphoid tissue
 Swallowing (pharynx/esophagus)
 All or none reflex, initiated when bolus is forced by tongue to rear of mouth
 Two stages
o Oropharyngeal stage
o Esophageal stage – bolus moves from mouth through pharynx into esophagus
o Teeth – mastication (chewing), first step in digestion
 Chewing
 Grind/break food into smaller pieces  makes swallowing easier, increase surface area
 Mix food with saliva
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 Stimulate taste buds
 Saliva – 99.5% water, 0.5% electrolytes and protein (amylase, lysozyme, mucus)
 Three glands contribute to its production: parotid, submandibular, sublingual
 Salivary amylase begins digestion of carbs
 Moistens food for swallowing and mucus lubricates
 Antibacterial – lysozyme destroys bacteria, food sources for bacteria destroyed
 Solvent to stimulate taste buds
 Aids in speech by allowing movement of lips/tongue
 Keeps mouth and teeth clean
 Rich in bicarbonate buffer
Esophagus
 Straight, muscular tube that extends between pharynx and stomach
 Sphincters at each end
 Pharyngoesophageal sphincter – prevents air from entering esophagus during breathing
 Gastroesophageal sphincter – prevents reflux of gastric contents
 Peristaltic waves push food through, mucus is only protective
Stomach
 Three sections – fundus, body, antrum
 Functions
 Store ingested food
 Secrete HCl and enzymes to begin protein digestion
 Mixing converts food to chime
 Pyloric sphincter – barrier between stomach and duodenum
 Motility
 Filling – receptive relaxation: stomach is able to accommodate food without increasing pressure,
trigger by act of eating, regulated by vagus nerve
 Storage – in body
 Mixing – in antrum
 Emptying – controlled by duodenum
o Amount of chime is main factor influencing strength of contraction
o Duodenum factors
 Fat – if fat is in duodenum, further movement prevented (only place where fat
is digested/absorbed)
 Acid – inhibits movement until neutralization
 Hypertonicity – inhibits movement
 Distension – inhibits movement
o Other factors
 Neural – intrinsic nerve plexus (short reflex) and autonomic nerve (long reflex)
 Hormonal – from duodenal mucosa called enterogastrones
 Emotions – sadness/fear=decrease, anger/aggression=increase
 Pain – inhibit movement
 Secretions
 Oxyntic mucosa – lines body and fundus
 Pyloric gland area (PGA) – lines antrum
 Exocrine secretory cells
o Mucous cells – line gastric pits and entrance of glands, thin/watery mucus
o Chief cells – secrete enzyme precursor, pepsinogen
o Parietal (oxyntic) cells – secrete HCl and intrinsic factor
 HCl – activates pepsinogen to pepsin, provides acid media for optimal activity,
breakdowns connective tissue and muscle fibers, denatures protein, kills
microorganisms in food
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Phases
 Cephalic – increased secretions of HCl and pepsinogen that occurs in response to stimuli acting
in brain before food reaches stomach
 Gastric – begins when food reaches stomach, presence of protein increases gastric secretions
 Intestinal – inhibitory phase when gastric juices are shut off as chyme moves to small intestine
Pancreas
 Mix of endocrine and exocrine function, located behind and below stomach
 Endocrine – Islet of Langerhans: secretes insulin and glucagon
 Exocrine
o Acinar cells - secretes pancreatic enzymes
o Duct cells – secrete aqueous alkaline solution that line pancreatic ducts
o Regulated by secretin and CCK
o Proteolytic enzymes – digest protein
 Trypsinogen  trypsin
 Chymotrypsinogen  chymotrypsin
 Procarboxypeptidase  carboxypeptidase
o Pancreatic amylase – converts polysaccharides to disaccharide amylase
o Pancreatic lipase – only enzyme in digestive system that can digest fats
Liver
 Largest, most important metabolic organ (biochemical factory)
 Role is digestion is secretion of bile salts
 Other functions
 Metabolic processing of nutrients and storing them as glycogen, fat, iron, copper, vitamins
 Detox waste, hormones, drugs, foreign compounds
 Synthesize plasma protein
 Activate Vitamin D
 Removes bacteria and old RBC’s
 Excretes cholesterol and bilirubin
 Bile
 Secreted by liver and diverted to gallbladder between meals (stored and concentrated here)
 Consists of bile salts, cholesterol, lecithin, bilirubin
 Bile Salts
o Derivatives of cholesterol
o Convert large fat globules into a liquid emulsion
o Reabsorbed into blood
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Small Intestine
 Site where most digestion and absorption occurs
 Three segments: duodenum, jejunum, ileum
 Motility
 Segmentation
o Primary method consisting of ring like contractions along length
o Within seconds, contracted segments relax and previously relaxed areas contract
o Action mixes chyme throughout small intestine
o Initiated by pacemaker cells which produce basic electrical rhythm (BER)
o Circular smooth muscle responsiveness is influenced by distension of intestine, gastrin
and extrinsic nerve activity
 Migrating motility complex – sweeps intestine clean between meals
 Secretion
 Gastric juices do not contain any digestive enzymes
 Synthesized enzymes work within brush border membrane of epithelial cells
o Enterokinase, disaccharidases, aminopeptidases
 Digestion
 Pancreatic enzymes continue carb and protein break-down
 Brush border enzymes complete digestion of carbs and protein
 Fat is digested completely within lumen by pancreatic lipase
 Absorption
 Absorbs almost everything presented in duodenum and jejunum
 Adaptations increase surface area – permanent circular folds, finger-like projections called villi
and brush border (microvilli) arise from luminal surface of epithelial cells
 Lining is replaced every three days
 Products of fat digestion are transformed to be passively absorbed into lymph
Large Intestine
 Primarily a drying/storage organ
 Consist of colon, cecum, appendix, rectum
 Contents received consist of indigestible food residue, unabsorbed biliary components and fluid
 Colon
 Extracts water and salt from contents
 Feces remains to be excreted
 Taeniae coli – longitudinal bands of muscle
 Haustra – pouches/sacs, actively change location as a result of contraction of circular smooth muscle
 Haustral contractions – main motility, initiated by autonomic rythmiticity of colonic smooth
muscle cells
 Mass movements – massive contractions, moves colonic contents into end of large intestine
 Gastrocolic reflex – mediated from stomach to colon by gastrin and autonomic nerves, most evident
after first meal of day, followed by urge to defecate
 Defecation reflex
 stretch receptors in rectal wall are stimulated by distension
 internal anal sphincter relaxes, rectum and sigmoid colon contract vigorously
 if external anal sphincter is also relaxed, defecation occurs
GI hormones
 Gastrin
 Release is stimulated by presence of protein in stomach
 Secretion inhibited by accumulation of acid on stomach
 Function
o Increase secretion of pepsin and HCl
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Nutrients
Carbohydrates
Enhance gastric motility, stimulate ileal motility, relax ileococcal sphincter, induce mass
movement in colon
Maintain viable digestive tract lining
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Secretin
o Presence of acid in duodenum stimulates release
o Function
 Inhibits gastric emptying so no acid can enter duodenum until remaining acid
is neutralized
 Inhibits gastric secretion to reduce amount of acid produced
 Stimulate pancreatic duct cells to produce aqueous NaHCO3
 Stimulate liver to produce NaCO3 rich bile to assist in neutralizing
 Trophic to exocrine pancreas, like CCK
CCK
o Functions
 Inhibit gastric motility and secretion
 Stimulate pancreatic Acinar cells to make more pancreatic enzyme
 Contraction of gall bladder and relax Sphincter of Oddi
 Trophic to exocrine pancreas, like secretin
 Long-term adaptive changes associated with change of diet in pancreatic
enzymes
 Regulator of food intake
GIP (glucose dependent insulinotrophic peptide)
o Stimulates insulin release by pancreas
Enzymes for
Digesting Nutrients
Amylase
Source of Enzyme
Salivary glands
Exocrine pancreas
Protein
Fat
Site of Action of
Enzyme
Mouth, body of
stomach
Lumen of small
intestine
Action of Enzyme
Hydrolyzes
polysaccharides to
disaccharides
Hydrolyze protein
to peptide fragment
Absorbable Units of
Nutrients
Hydrolyzes
polysaccharides to
disaccharides
Disaccharidases
Epithelial cells of
small intestine
Brush border of
small intestine
Pepsin
Stomach chief cells
Stomach antrum
Trypsin,
chymotrypsin,
carboxypeptidase
Exocrine pancreas
Lumen of small
intestine
Attack different
peptide fragments
Aminopeptidases
Epithelial cells of
small intestine
Brush border of
small intestine
Lipase
Exocrine pancreas
Lumen of small
intestine
Hydrolyze peptide
fragments to amino
acids
Hydrolyze
triglyceride to fatty
acid and
monoglycerides
Bile salts (not an
enzyme)
Liver
Lumen of small
intestine
Emulsify large fat
globules for attack
by pancreatic lipase
Monosaccharides
(esp. glucose)
Amino acids and
few small peptides
Fatty acids and
monoglycerides
Skin
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Function
o Protection chemically, physically and mechanically
o Body temperature regulation
 Dilation-cooling, constriction-warming of vessels
 Increasing secretions by sweat glands
o Cutaneous sensation – touch and pain
o Synthesis of vitamin D in blood vessels
o Stores 5% of blood as reservoir
o Nitrogenous waste excreted from body in sweat
Three major regions
o Epidermis – outermost, superficial
 Made of keratinized stratified squamous epithelium
 Cell types include keratinocytes, melanocytes, Merkel cells, Langerhan cells
 Keratinocyte – produce fibrous keratin
 Melanocyte – produce brown pigment melanin
 Langerhan cell – macrophage that helps activate immune system
 Merkel cell – touch receptors in association with sensory nerve endings
 Exposed to external environment, functions in protection
 Layers
 Stratum basale – attached to dermis, single row of young keratinocytes, rapid cell division
 Stratum spinosum – “prickly layer”, web-like system attached to desmosomes, many melanin
granules and Langerhan cells
 Stratum granulosum – drastic changes in keratinocyte appearance
 Stratum lucidum – transparent, flat, dead keratinocytes, only present in thick skin
 Stratum corneum – outermost layer, accounts for most of epidermal thickness, helps to waterproof,
protect from abrasion/penetration, makes body insensitive to assault
o Dermis – middle region
 Contains strong, flexible tissue
 Cells include fibroblasts, macrophages, mast cells and WBC
 Two layers
 Papillary
o Areolar connective tissue with collagen and elastic fibers
o Peg-like projections called dermal papillae – have capillary loops, Meissner corpuscle, free
nerve endings
 Reticular
o Accounts for 80% of thickness of skin
o Add strength and resiliency (elastin-stretch/coil properties)
o Hypodermis – deepest
 Subcutaneous layer composed of adipose tissue and areolar connective tissue
Skin color
o Three pigments contribute
 Melanin – yellow to red-brown to black (dark skin colors)
 Moles are local accumulation of melanin
 Carotene – yellow to orange, obvious in palms and soles of feet
 Hemoglobin – reddish responsible for pinkish hue
Sweat glands – prevent overheating
o Eccrine – in palms, soles of feet and forehead
o Aprocrine – axillary and anogenital areas
o Ceruminous – modified apocrine gland in external ear canal
o Mammary – modified secreting milk
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Sebaceous gland
o Simple alveolar glands found everywhere
o Soften skin when stimulated by hormones by secreting oily secretion called sebum
Hair
o Filamentous strands of dead keratinized cells produced by hair follicles
o Hard keratin is tougher and more durable
o Has a shaft projecting from skin and root embedded in the skin
o Has a medulla, cortex and outmost cuticle
o Pigmented by melanocytes at base of hair
o Function
 Maintain warmth
 Alert the body to presence of insects on skin
 Guard scalp again physical trauma, heat loss and sunlight
o Present everywhere except palms, soles, lips, nipples and portions of external genitalia
o Hair follicle
 Root sheath extends from epidermal surface into dermis
 Deep end expands to form hair bulb where a root hair plexus (knot of sensory nerve endings) wraps around
 Bending a hair stimulates these endings – hair is also a touch receptor
o Types
 Vellus – pale, fine found in children and adult female
 Terminal – course long found in eyebrows, scalp, axillary and pubic
o Thinning/baldness
 Alopecia – hair thinning in both sexes
 True/frank baldness – genetically determined, sex-influenced
 Male pattern – caused by follicular response to DHT
Nail
o Scale-like modification of the epidermis on toes and fingers
o
Skin cancer
o Most tumors are benign and do NOT metastasize
o Crucial risk factor for nonmelanoma cancer is disabling of p53 gene
o Newly developed skin lotions can fix damaged DNA
o Types
 Basal cell carcinoma
 Least malignant, most common
 Stratum basale cells proliferate and invade dermis and hypodermis
 Slow growing, usually no NOT metastasize
 Usually cured by surgical excision in 99% of cases
 Squamous cell carcinoma
 Arises from keratinocytes of stratum spinosum
 Usually found on scalp, ears and lower lips
 Grows rapidly, metastasizes if not removed
 Prognosis is good if removed surgically or treated by radiation
 melanoma
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burns
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most dangerous, highly metastatic
resistant to chemotherapy
use ABCD rule – asymmetry, border (irregular), color, diameter (> 6 mm)
treated by surgical excision and immunotherapy
if lesion is over 4 mm thick, chance of survival is low
First degree – epidermis only damaged, localized redness/swelling/pain
Second degree – epidermis and upper regions of dermis damaged, looks like first degree burn with blisters
Third degree – entire thickness of skin damaged, looks gray-white, cherry red or black, no initial edema/pain because
nerve endings are destroyed
o Use Rule of Nines to determine if critical
 Over 25% of body has second degree burns
 Over 10% of body has third degree burns
 There are third degree burns on face, hands, or feet
Developmental
o Infant
 Epidermis developed from ectoderm
 Dermis and hypodermis developed from mesoderm
 Lanugo – coat of delicate hair covering fetus
 Vernix caseosa – substance produced by sebaceous glands that protect skins of fetus in the amnion
o Adolescent
 Skin are hair become oilier, acne
 Skin shows cumulative environmental assault at age 30
 Scaling and dermatitis become more common
o Elderly
 Epidermal replacement slows, skin becomes thinner
 Skin becomes itchy and dry
 Subcutaneous fat diminishes leading to intolerance to cold
 Decreased elasticity and loss of subcutaneous tissue leads to wrinkles
 Decreased number of melanocytes and Langerhan cells increase risk for skin cancer