A&P II - Exam 3

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A dust particle is inhaled and gets into an alveolus without being trapped along the way. Describe the path it takes, naming all air passages from external naris to alveolus. What would happen to it after arrival in the alveolus?

>external naris > vestibule > nasal cavity > nasopharynx > oropharynx > laryngopharynx > larynx > trachea > main bronchi > lobar bronchi > segmental bronchi > bronchioles > respiratory brochioles > alveolar ducts > atrium > alveoli

>> it would be phagocytized by alveolar macrophages (dust cells)

Describe the histology of the epithelium and lamina propria of the nasal cavity and the functions of the cell types present.

- olfactory - cilia bind odor particles

-respiratory epithelium - ciliated (mobile), pseudostratified columnar epithelium > goblet cells secrete mucus & its ciliated cells propel the mucus toward pharynx

- lamina propria - blood vessels & lymphocytes for defense & moisturizing air

Describe the roles of the intrinsic muscles, conciliate cartilages, and arytenoids cartilages in speech.

- intrinsic muscles - control vocal cords by pulling on the conciliate & arytenoid cartilages, causing them to pivot > forcing air between them so they vibrate

- arytenoids - adduct/abduct vocal cords, depending on direction of rotation

Contrast the epithelium of the brochioles with that of the alveoli and explain how the structural difference is related to their functional difference.

- BRONCHOLES - ciliated cuboidal epithelium to move mucus & a well developed layer of smooth muscle

- ALVEOLI - thin, broad cells (squamous alveolar cells) - thinness allows for rapid gas diffusion between air & blood
> Type 2 cuboidal cells (great alveolar cells) - repair alveolar epithelium, secrete pulmonary surfactant

Explain why contraction of the diaphragm causes inspiration but contraction of the transverse abdominal muscle causes expiration.

-CONTRACTION OF DIAPHRAGM - tenses and flattens > enlarges dimensions of throacic cavity > decreases its internal pressure and produces an inflow of air

-ABDOMINAL MUSCLE - increase pressure in abdominal cavity and pushes up some viscera up against diaphragm

Which brainstem respiratory nucleus is indispensable to respiration?

Ventral Respiratory Group (VRG) - elongated nucleus in medulla > generates rhythm of breathing

Explain why Boyle's law is relevant to the action of the respiratory muscles.

>> at a constant temperature, the pressure of a given quantity of gas in INVERSELY proportional to its volume

>respiratory muscles contract > increase space > decrease pressure > forcing air in

Explain why eupnoea requires little or no action by the muscles of expiration.

due to elastic recoil of lungs

Identify a benefit and a disadvantage of normal (non-pathological) bronchoconstriction.

protection from damage due to heat loss in cold BUT can be bad if brought about the asthma or anaphylactic shock

Why is the composition of alveolar air different from that of the atmosphere?

1) it is humidified by contact w/mucous membranes

2) it mixes with residual air left from previous respiratory cycle (O2 is diluted and enriched with CO2)

3) it exchanges O2 and CO2 with the blood

What 4 factors affect the efficiency of alveolar gas exchange?

1) pressure gradients of the gasses

2) solubility of gasses

3) membrane thickness

4) membrane area

Explain how perfusion of a pulmonary lobule changes if it is poorly ventilated.

it stimulates local vasoconstrictors > redirecting blood to better ventilated areas of lung

How is most oxygen transported in the blood? Why does carbon monoxide interfere with this?

- hemoglobin > binds 95% of O2

- CO competes with O2 for the same binding site > binds 210x as tightly, tying up hemoglobin for a long time, preventing uptake

What are 3 ways in which blood transports CO2?

1) attached to hemoglobin

2) carbonic acid > bicarbonate buffer system

3) dissolved gas

Give 2 reasons why highly active tissues can extract more oxygen from the blood than less active tissues.

1) active tissues release more CO2 that reacts to produce bicarbonate & H > the H causes hemoglobin to release more O2

2) they are warmer

Define hypocapnia and hypercapnia. Name the pH imbalances that result from these conditions and explain the relationship between Pco2 and pH.

-HYPOCAPNIA - Pco2 less than 37mm Hg (most common cause of alkalosis: blood pH>7.45)

- HYPERCAPNIA - Pco2 greater than 43mm Hg (most common cause of acidosis: blood pH<7.35)

What is the most potent chemical stimulus to respiration, and where are the most effective chemoreceptors for it located?

- pH - central chemoreceptors in brain

Explain how changes in pulmonary ventilation can correct pH imbalances.

if blood is too acidic, like seen in diabetics, respiration rate increases, blowing off extra CO2 & increasing pH

Describe the 4 classes of hypoxia

1) HYPOXEMIC - inadequate pulmonary gas exchange - low arterial Po2
>high altitude, drowning, respiratory arrest, degenerative lung disease, CO poisoning

2) ISCHEMIC - inadequate circulation
>congestive heart failure

3) ANEMIC - inability of blood to carry adequate O2

4) HISTOTOXIC - metabolic poison prevents tissues from using O2 delivered to them
>cyanide poisoning

Name and compare 2 COPDs and describe some pathological effects that they have in common.

1) CHRONIC BRONCHITIS - produce excess mucus - cilia are immobilized and reduces in number while goblet cells enlarge
>increase infection, swelling

2) EMPHYSEMA - alveolar walls break down and the lungs exhibit larger but fewer alveoli > there is much less respiratory membrane available for gas exchange
>less elasticity of lungs

In what lung tissue does lung cancer originate? How does it kill?

- mucous membranes of the large bronchi

> as a tumor invades the bronchial wall and grows around it, it compresses the airway and may cause collapse of more distal parts of lung

3 meanings of respiration

1) ventilation of the lungs (breathing)

2) the exchange of gases between the air and blood, and between blood and the tissue fluid

3) the use of oxygen in cellular metabolism

functions of the respiratory system

- O2 and CO2 exchange between blood and air
- speech
- smell
- affect pH of body fluids by eliminating CO2 (makes blood acidic)
- affects blood pressure (synthesis of vasoconstrictor, angiotensin II)
- breathing creates pressure gradients between thorax and abdomen that promote the flow of lymph and venous blood)
- breath-holding helps expel abdominal contents (valsalva maneuver)

principal organs of respiratory system

nose, pharynx, larynx, trachea, bronchi, lungs

respiratory division of the respiratory system

alveloi and other gas exchange regions

upper respiratory tract

- in head and neck

-nose through larynx

lower respiratory tract

- organs of the thorax

-trachea through lungs

the nose (functions)

- warms, cleanses, and humidifies inhaled air

-detects odors in the airstream

- serves as a resonating chamber that amplifies the voice

nasal fossae

right and left halves of the nasal cavity

> nasal septum - divides nasal cavity > composed of bone and hyaline cartilage

> paranasal sinuses and nasolacrimal duct drain into nasal cavity

vestibule

- beginning of nasal cavity (small dilated chamber just inside nostrils)

- vibrissae - stiff guard hairs that block insects and debris from entering nose

olfactory epithelium

- detect odors

-ciliated pseudostratified columnar epithelium w/goblet cells >>immobile cilia to bind odorant molecules

respiratory epithelium

- lines rest of nasal cavity except vestibule

- pseudostratified ciliated columnar epithelium w/goblet cells >>motile cilia > goblet cells secrete mucus & cilia propel the mucous posteriorly toward pharynx > swallowed into digestive tract

pharynx

- THROAT - a muscular funnel extending about 13cm from the choanae to the larynx

3 regions of pharynx

1) nasopharynx - receives auditory tubes and contains pharyngeal tonsil
> passes ONLY air and is lined by pseudostrat. columnar epi.
> 90' downward turn traps large particles

2) oropharynx - contains palatine tonsils

3) laryngopharynx - epiglottis to cricoid cartilage > esophagus begins at that point

>>oro. and laryngo. pass air, food, and drink and are lined by strat. squamous

larynx

- VOICE BOX - cartilaginous chamber

- primary function - to keep food and drink out of the airway
> phonation - production of sound

- epiglottis - closes airway and directs food to the esophagus behind it
> vestibular folds of larynx play greater role in keeping food and drink out of the airway

>> framework made up of 9 cartilages

walls of larynx

- deep intrinsic muscles - operate vocal cords

- superior extrinsic muscles - connect larynx to hyoid bone > elevate larynx during swallowing

- superior vestibular folds - play no role in speech > close larynx during swallowing

-inferior vocal cords - produce sound when air passes between them
> contain vocal ligaments
> covered with strat. squamous - best suited to endure vibration and contact between the cords

glottis

the vocal cords and the opening between them

action of vocal cords

- controlled by intrinsic muscles
- air forced between adducted vocal cords vibrates them
> taut - high pitch
> more slack - lower pitch

-adult male cords are: usually longer and thicker, vibrate more slowly, produce lower pitched sound

>LOUDNESS is determined by the force of air passing between the vocal cords

> vocal cords produce CRUDE SOUNDS that are formed into words by actions of pharynx, oral cavity, tongue, and lips

trachea

-WINDPIPE - anterior to esophagus
-supported by C-shaped rings of hyaline cartilage > reinforces trachea and keeps it from collapsing when you inhale

> trachealis muscle spans opening in rings

tracheostomy

- to make a temporary opening in the trachea inferior to the larynx and insert a tube to allow airflow

> prevents asphyxiation due to upper airway obstruction

lungs

-right - shorter than L because the liver rises higher on the right >> 3 lobes

- left - taller and narrower because the heart tilts toward the L and occupies more space on this side of mediastinum >> 2 lobes
> has indentation - cardiac impression

path of air flow

nasal cavity > pharynx > larynx > trachea > main bronchus > lobar bronchus > segmental bronchus > bronchiole > terminal bronchiole > respiratory division > respiratory bronchiole > alveolar duct > atrium > alveolus

alveoli

-150mil in each lung

-squamous (type I) cells - thin, broad > allow for rapid gas diffusion between alveolus and bloodstream
>95% of alveolus surface area

- great (type II) cells - round to cuboidal > repair alveolar epithelium when squamous cells are damaged
** secrete PULMONARY SURFACTANT - mixture of phospholipids and proteins that coats the alveoli and prevents them from collapsing when we exhale

- alveolar macrophages (dust cells) - most numerous of all cells in the lung; wander the lumen and connective tissue between alveoli > phagocytize dust particles
> 100mil dust cells perish each day as they ride up the mucocilary escalator to be swallowed and digested with their load of debris

respiratory membrane

- the barrier between the alveolar air and blood

- each alveolus surrounded by a basket of blood capillaries supplied by the pulmonary artery

> important to prevent fluid from accumulating in alveoli: alveoli are kept dry by absorption of excess liquid by blood capillaries

the pleurae and pleural fluid

- visceral pleura - serous membrane that covers lungs

- parietal pleura - adheres to mediastinum, inner surface of the rib cage, and superior surface of the diaphragm

- pleural fluid - film between membranes

> functions of pleurae and pleural fluid:
1) reduce friction
2) create pressure gradient - lower pressure than atmospheric pressure and assists lung inflation
3) compartmentalization - prevents spread of infection from one organ in the mediastinum to others

pulmonary ventilation

- everytime you take a breath > breathing consists of a repetitive cycle one cycle of inspiration and expiration

respiratory cycle

- one complete inspiration and expiration

quiet respiration

- while at rest, effortless, and automatic

forced expiration

- deep rapid breathing, such as during exercise

pressure difference

flow of air in and out of lung depends on a pressure difference between air pressure within lungs and outside the body

diaphragm

PRIME MOVER OF RESPIRATION

- contraction flattens diaphragm, enlarging thoracic cavity and pulling air into lungs

- relaxation allows diaphragm to bulge upward again, compressing the lungs and expelling air

> accounts for 2/3 of air flow

internal and external intercostal muscles

- between ribs - synergist to diaphragm

- stiffen the thoracic cage during respiration > prevents it from caving inward when diaphragm descends

- contribute to enlargement and contraction of throacic cage

- adds about 1/3 of the air that ventilates the lungs

scalenes

- synergist to diaphragm

- QUIET RESPIRATION - holds ribs 1 and 2 stationary

accessory muscles

of respiration act mainly in FORCED respiration

forced inspiration

greatly increase thoracic volume

normal quiet expiration

- an energy-saving PASSIVE process achieved by the elasticity (elastic RECOIL) of the lungs and thoracic cage

- as muscles relax, structures recoil to original shape and original size of thoracic cavity > results in air flow out of the lungs

forced expiration

- greatly increased abdominal pressure pushes viscera up against diaphragm increasing thoracic pressure, forcing air OUT

valsalva maneuver

consists of taking a deep breath, holding it by closing the glottis, and then contracting the abdominal muscles to raise abdominal pressure and pushing organ contents out

>> childbirth, urination, defecation, vomiting

hyperventilation

anxiety triggered state in which breathing is so rapid that it expels CO2 from the body faster than it is produced > as blood CO2 levels drop, the pH rises, causing the cerebral arteries to constrict reducing cerebral perfusion which may cause dizziness or fainting

> can be brought under control by having the person rebreathe the expired CO2 from a paper bag

central chemoreceptors

brainstem neurons that respond to changes in pH of cerebrospinal fluid

> pH of cerebrospinal fluid reflects the CO2 level in the blood >> by regulating respiration to maintain stable pH, respiratory center also ensures stable CO2 level in the blood

peripheral chemoreceptors

located in carotid and aortic bodies of the large arteries above the heart >> respond to the O2 and CO2 content and the pH of blood

pressure and airflow

- respiratory airflow is governed by the same principles of flow, pressure and resistance as blood flow

> the flow of a fluid is directly proportional to the pressure difference between two points

> the flow of a fluid is inversely proportional to the resistance

- ATMOSPHERIC PRESSURE drives respiration > the weight of the air above us

Boyle's law

- at a CONSTANT temperature, the pressure of a given quantity of gas in INVERSELY proportional to its volume

> if the lung volume increases, the internal pressure (intrapulmonary pressure) falls & vice versa

inspiration

- the 2 pleural layers, their cohesive attraction to each other, and their connections to the lungs and their lining of the rib cage bring about inspiration

> the entire lung expands along the thoracic cage > as it increases in volume, its internal pressure drops and air flows in

Charles' Law

the given quantity of gas is DIRECTLY proportional to its absolute TEMPERATURE

- thermal expansion will contribute to the inflation of the lungs

expiration - relaxed breathing

- passive process achieved mainly by the elastic recoil of the thoracic cage

> volume of thoracic cavity decreases
- raises intrapulmonary pressure
- air flows down the pressure gradient and out of the lungs

expiration - forced breathing

- accessory muscles raise intrapulmonary pressure as

- massive amounts of air moves out of the lungs

determinants of airflow

1) pressure

2) resistance > the greater the resistance, the slower the flow

3 factors influencing airway resistance

1) diameter of bronchioles - bronchodilation or bronchoconstriction

2) pulmonary compliance - the ease with which the lungs can expand

3) surface tension of the alveoli and distal bronchioles
>> surfactant - reduces surface tension of water

alveolar surface tension

- thin film of water needed for gas exchange

-pulmonary surfactant produced by the great alveolar cells > decreases surface tension by disrupting the hydrogen bonding in water

alveolar ventilation

- only air that enters the alveoli is available for gas exchange, not all inhaled air gets there

alveolar ventilation rate - AVR

= air the ventilates alveoli (350mL) x respiratory rate (12bpm) = 4200 mL/min

>> of all the measurements, this one is most directly relevant to the body's ability to get oxygen to the tissues and dispose of carbon dioxide

residual volume

= 1300 mL that CANNOT be exhaled with max. effort

respiratory volume - TIDAL VOLUME

- volume of air inhaled and exhaled in one cycle during QUIET breathing (500mL)

>> normal, relaxed breathing

respiratory volume - INSPIRATORY RESERVE VOLUME

- air in excess of tidal volume that can be inhaled with maximum effort (3000mL)

respiratory volume - EXPIRATORY RESERVE VOLUME

- air in EXCESS of TV that can be exhaled with maximum effort (1200mL)

respiratory volume - RESIDUAL VOLUME

- air remaining in lungs after maximum expiration (1300mL)

spirometry

- the measurement of pulmonary function

> aid in diagnosis and assessment of restrictive and obstructive lung disorders

restrictive disorders

- those that reduce pulmonary compliance

> limit the amount to which the lungs can be inflated
- any disease that produces pulmonary fibrosis (elastic tissue replaced with scar tissue)

-black-lung, tuberculosis

obstructive disorders

- those that interfere with airflow by narrowing or blocking the airway

eupnea

relaxed, quiet breathing

apnea

temporary cessation of breathing

dyspnea

labored, gasping breathing; shortness of breath

hyperpnea

increased rate and depth of breathing in response to exercise, pain, or other conditions

hyperventilation

increased pulmonary ventilation in excess of metabolic demand

hypoventilation

reduced pulmonary ventilation

Kussmaul respiration

deep, rapid breathing often induced by acidosis

orthopnea

dyspnea that occurs when a person is lying down

composition of air

-78.6% nitrogen
- 20.9% Oxygen
- 0.04% CO2
- 0-4% water vapor (depending on temp and humidity) and minor gases (argon, neon, helium, methane and ozone)

Dalton's law

the total atmospheric pressure is the sum of the contributions of the individual gases

differences in composition of inspired and alveolar air

1) air is humidified by contact with mucous membranes

2) freshly inspired air mixes with residual air left from the previous respiratory cycle

3) alveolar air exchanges O2 and CO2 with the blood

alveolar gas exchange

- the back and forth traffic of O2 and CO2 across alveolar epithelium

- air in the alveolus is in contact with a film of water covering the alveolar epithelium

for oxygen to get into the blood

it must dissove in the film of water & pass through the respiratory membrane separating the air from the bloodstream

> gases diffuse down their own concentration gradient until the partial pressure of each gas in the air is equal to its partial pressure in water

for carbon dioxide to leave the blood

it must pass the other way > diffuse out of the water film into the alveolar air

factors affecting gas exchange

1) pressure gradient of the gases

2) solubility of the gases
> CO2 is 20X as soluble as O2
> O2 is 2X as soluble as N2

3) membrane thickness

4) membrane surface area

ventilation-perfusion coupling

the ability to match ventilation and perfusion to each other
> gas exchange requires both good ventilation of alveolus and good perfusion of the capillaries

oxygen transport

- 95% bound to hemoglobin in RBC

- 1.5% dissolved in plasma

carbon dioxide transport

- 70% as bicarbonate ion

- 23% bound to hemoglobin

- 7% dissolved in plasma

carbon monoxide poisoning

- CO competes for the O2 binding sites on the hemoglobin molecule

- binds 210x as tightly as o'xygen > ties up hemoglobin for a long time

systemic gas exchange

- the unloading of O2 and loading of CO2 at the systemic capillaries

CO2 loading > chloride shift

- Cl has to moved around in order for RBC to pick up unload CO2

adjustment to the metabolic needs of individual tissues

hemoglobin unloads O2 to match metabolic needs of different states of activity of the tissues

4 factors that adjust the rate of oxygen unloading

1) ambient PO2 - active tissue has decreased PO2; O2 is released from Hb

2) temperature - active tissue has increased temperature > promotes unloading

3) Bohr effect - active tissure has increased CO2 > lowers pH of blood > promoting O2 unloading

4) bisphosphoglycerate (BPC) - RBCs produce BPG which binds to Hb > O2 is unloaded

rate and depth of breathing adjust to maintain levels of

in this order:

1) pH - 7.35-7.45 (75% of the change in respiration induced by pH shift)

2) PCO2 - 40mm Hg

3) PO2 - 25mm Hg

respiration acidosis/ respiratory alkalosis

pH imbalances resulting from a mismatch between the rate of pulmonary ventilation and the rate of CO2 production

hyperventilation

- a corrective homeostatic response to acidosis
> "blowing offf" CO2 faster than the body produces it

hypoxia

deficiency of oxygen in a tissue or the inability to use oxygen

> a consequence of respiratory disseases

State 4 functions of the kidneys other than forming urine.

1) filter blood plasma and excrete metabolic toxic wastes

2) regulate blood volume, pressure, and osmolarity by regulating H2O output

3) secrete erythropoietin

4) regulate electrolyte and acid-base balance of body fluids

5) calcium homeostasis

List 4 nitrogenous wastes and their metabolic sources.

1) UREA > byproduct of protein catabolism
2) AMMONIA > proteins
3) URIC ACID > nucleic acids
4) CREATININE > creatine phosphate

Name some wastes eliminated by 3 systems other than the urinary system.

1) respiratory > CO2, water, other gases

2) integumentary > water, inorganic salts, lactic acid, urea in sweat

3) digestive > water, salts, CO2, lipids, bile pigments, cholesterol, food residue

Arrange the following in order from the MOST numerous to the LEAST numerous structures in a kidney: glomeration, major calyces, minor calyces, interlobular arteries, interlobar arteries.

glomeruli > interlobular A > interlobar > minor calyces > major calyces

Trace the path taken by one RBC from the renal artery to the renal vein.

renal A > segmental A > interlobar A > arcuate A > interlobular A > afferent arterioles > glomerulus > efferent arterioles > peritubular capillaries > interlobular V > arcuate V > interlobar V > renal vein

Consider one molecule of urea in the urine. Trace the route that it took from the point when it left the bloodstream to the point where it left the body.

glomerular capsule > proximal convoluted tubule > nephron loop > distal convoluted tubule > collecting duct > papillary duct > minor calyx > major calyx > renal pelvis > ureter > urinary bladder > urethra

Name the 4 major processes in urine production.

1) glomerular filtration - creates plasma-like filtrate of blood

2) tubular reabsorption - removes useful solutes from filtrate, returns them to the blood

3) tubular secreation - removes additional wastes from blood, adds them to the filtrate

4) water conservation - removes water from the urine and returns it to blood; concentrates wastes

Trace the movement of a urea molecule from the blood to the capsular space and name the barriers it passes through.

fenestrated capillary endothelium > negatively charged basement membrane > podocyte filtration slits

Calculate the net filtration pressure in a patient whose blood COP is only 10mm Hg because of hypoproteinemia. Assume other relevant variable to be normal.

> outward pressure - hydrostatic pressure - colloid osmotic pressure
> 60out - 18in - 10in = 32mm Hg out

Assume a person is moderately dehydrated and has low blood pressure. Describe the homeostatic mechanisms that would help the kidneys maintain a normal GPR.

- low BP > the afferent arteriole relaxes, allowing more blood in (to a point); they (J cells) also secrete renin to increase BP

- dehydration > the renin/angiotensin system triggers thirst and sodium/water retention/reabsorption so waste is removed but H2O is kept

The reabsorption of water, CL, and glucose by the PCT is linked to the reabsorption of Na, but in three very different ways. Contrast these 3 mechanisms.

1) WATER - follows solutes by osmosis through both PARACELLULAR and transcellular routes (aquaporins)

2) CHLORIDE - negatively charged are attracted to Na+ and follow into cell through ANTIPORTS

3) GLUCOSE - cotransported win Na+ by SYMPORTS (SGLTs)

Explain why a substance appears in the urine if its rate of glomerular filtration exceeds the Tm of the renal tubule.

If the amount of a substance is so high that its levels exceed the ability to transport it out, some will be left in the urine >> saturation of transport proteins

Contrast the effects of aldosterone and ANP on the renal tubule.

- ALDOSTERONE - causes tubules to absorb more Na+ and secrete more K+ >> H2O follows Cl- > follows Na+

- ANP (natriuretic peptides) - dilates afferent arterioles, inhibits NaCl reabsorption

Predict how ADH hypersecretion would affect the sodium concentration of the urine and explain why.

- increase in ADH causes H2O absorption by INCREASING aquaporins, leaving sodium behind in tubular fluid

Concisely contrast the role of the countercurrent multiplier with that of the countercurrent exchange.

- countercurrent MULTIPLIER (of nephron loop) - recaptures salt and returns it to the deep medullary tissue > increasing salinity & osmolarity

- countercurrent EXCHANGE (blood vessel) - preserves salinity by blood vessel that takes up NaCl > also excretes NaCl, balancing out levels and not decreasing osmolarity

How would the function of the collecting duct change if the nephron loop did not exist?

would have to absorb MORE H2O and secrete LESS urea

Define oliguria and polyuria. Which of these is a characteristic of diabetes?

- OLIGURIA - urine output < 500mL/day

- POLYURIA - urine output > 2L/day
*characteristic of diabetes*

Identify a cause of glycosuria other than diabetes mellitus.

gestational diabetes (due to decrease in insulin sensitivity)

How is the diuresis produced by furosemide like the diuresis produced by diabetes mellitus? How are they different?

- BOTH cause H2O not to be reabsorbed

- in diabetes the H2O follows glucose in uring and with lasics salt stays in urine so H2O follows that

Explain why GFR cannot be determined by measuring the amount of NaCl in the urine.

because NaCl is BOTH excreted and reabsorbed

Describe the location and function of the detrusor muscle.

muscle layer of bladder that contracts > urine

Compare and contrast the function of the internal and external urethral sphincters.

- INTERNAL - (smooth muscle) involuntary control - compresses urethra and retains urine in bladder

- EXTERNAL - (skeletal muscle) voluntary control - voiding of urine

In males, the sympathetic nervous system triggers ejaculation and, at the same time, stimulates constriction of the internal urethral sphincter. What purpose is served by the latter action?

prevents urine from mixing with sperm

"to live...

...is to metabolize"

> metabolism creates a variety of toxic waste products

urinary system

- principal means of waste removal

urinary system & reproductive system

- the two are closely associated >> "urogenital system"

> share embryonic development
> share adult anatomical relationship
> male urethra serves as a common passage for urine and sperm

organs of the urinary system

2 kidneys, 2 ureters, urinary bladder and urethra

functions of the kidney

1) filters blood plasma, separates waste from useful chemicals, returns useful substances to blood, ELIMINATES WASTES
> 20% of cardiac output filters through kidneys

2) regulate BLOOD VOLUME and PRESSURE by eliminating or conserving water

3) regulate OSMOLARITY of the body fluids by controlling the relative amounts of water and solutes eliminated

4) secretes enzyme, RENIN > activates hormonal mechanisms that control blood pressure and electrolyte balance

5) secretes the hormone, ERYTHROPOIETIN > stimulates production of RBCs

6) collaborate with lungs to regulate the PCO2 and ACID-BASE BALANCE of body fluids

7) final step in synthesizing CALCITRIOL > contributes to calcium homeostasis

8) GLUCOGENESIS - from amino acids in extreme starvation

waste

- any substance that is useless to the body or present in excess of the body's needs

metabolic waste

- waste substance produced by the body

urea formation

proteins > amino acids > NH2 removed > forms ammonia (toxic to the body) > liver converts to urea

excretion

- separation of wastes from body fluids and eliminating them

renal parenchyma

- glandular tissue that forms urine

- 2 zones: outer renal cortex & inner renal medulla

> encircles the renal sinus

renal sinus

- contains blood and lymphatic vessels, nerves, and urine-collecting structures
> adipose fills the remaining cavity and holds structures into place

renal circulation

> the kidneys account for only 0.4% of body weight but the receive about 21% of the cardiac output (renal fraction)

functional unit of the kidney

NEPHRON.
Interchange between blood and urine.

> composed of 2 parts:
1) renal corpuscle - filters the blood plasma
2) renal tubule - long coiled tube that converts the filtrate into urine
>> divided into 4 regions:
1-3) PCT, nephron loop, DCT
4) collecting duct - received fluid from many nephrons

renal innervation - renal plexus

- nerves and ganglia wrapped around each renal artery
> carries SYMPATHETIC innervation from the abdominal aortic plexus
>> stimulation reduces glomerular blood flow and rate of urine production
>> respond to falling blood pressure by stimulating the kidneys to secrete RENIN (an enzyme that activates hormonal mechanisms to restore blood pressure)

> carries PARASYMPATHETIC innervation from the vagus nerve >> increases rate of urine production

overview of urine formation

- kidneys convert blood plasma to urine in 3 stages:

1) glomerular filtration
2) tubular reabsorption and secretion
3) water conservation

glomerular filtration

- a special case of the capillary fluid exchange process in which water and some solutes in the blood plasma pass from the capillaries of the glomerulus into the capsular space of the nephron

filtration membrane

3 barriers through which fluid passes:

1) fenestrated endothelium of glomerular capillaries - 70-90nm filtration pores exclude blood cells; highly permeable

2) basement membrane - negative charge; excludes molecules greater than 8nm; albumin repelled by negative charge (blood plasma is 7% protein, filtrate is only 0.03%)

3) filtration slits -
> podocyte cell extension wrap around the capillaries to form a barrier layer with 30nm filtration slits
> negatively charged which is an additional obstacle for large anions

molecules that CAN pass through filtration membrane

- almost any molecule smaller than 3nm can pass freely through the filtration membrane
>> water, electrolytes, glucose, fatty acids, amino acids, nitrogenous wastes, vitamins

- some substances of low molecular weight are bound to the plasma proteins and cannot get through the membrane
>> most calcium, iron, and thyroid hormone > unbound fraction passes freely into the filtrate

kidney infections and trauma

- can damage the filtration membrane and allow albumin or blood cells to filter

> proteinuria - presence of protein in the urine
> hematuria - blood in urine

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