FSHN 251 Exam 1 - Urinary System

Origin of the urinary system

Mesoderm

Which cellular process is analogous to the urinary system?

Exocytosis

Exocytosis

The process in which an intracellular vacuole, containing waste products or substances that must be secreted, fuses with the membrane

Endocytosis

The process through which molecules are engulfed by the cell membrane, forming intracellular vesicles

Phagocytosis

Endocytosis of large particles

Pinocytosis

A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes

Receptor-mediated endocytosis

The movement of specific molecules into a cell by the inward budding of membranous vesicles containing proteins with receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances.

Four functions of the urinary system

1. Eliminate nitrogenous waste

2. Maintain water-salt balance in the blood

3. Maintain acid-base balance in the blood

4. Hormone secretion

Waste product of amino acids

Urea

Waste product of nucleic acids

Uric acid

Waste product of creatine

Creatinine

Eruremia

Urea in the blood

Problems associated with uremia

Cardiac arrhythmia, vomiting, potential death

Creatine

Energy storage molecule in the muscle + eliminated by urine

Uric acid

Metabolic process from nucleotides. Eliminated by urine. Insoluble and can crystallize in blood and joints

Gout

A type of joint inflammation characterized by deposits of uric acid crystals in the joints

Importance of salt in the blood

Influence the rate and direction of osmosis.

More salt = greater blood volume = greater BP

How do the kidneys regulate blood volume?

The kidneys regulate the concentration of Na+ and K+ in the blood, therefore regulating blood volume (more ions = greater water retention = greater blood volume)

Osmosis

Molecules of a solvent (typically water) pass across a semipermeable membrane

Hypertonic

Having a higher osmotic pressure compared to another solution

Isotonic

Having equal osmotic pressure on either side of the membrane

Hypotonic

Having a lower osmotic pressure compared to another solution

The kidneys regulate the concentration of which ions?

Na+, K+, HCO3-, Ca2+, H+

Healthy blood pH

7.35-7.45

Alkalosis

Blood pH above 7.45

Acidosis

Blood pH below 7.35

pH of urine

Usually 6 or below

Systems that regulate blood pH (3)

Acid-base buffer systems, respiratory center, kidneys

Buffer

A solution that resists moderate changes in pH. Can take up excess H+ and OH-

WHat is one of the most important buffers in blood?

carbonic acid (H2CO3) and bicarbonate (HCO3-)

Proton neutralization

H+ + HCO3- -> H2CO3

Hydroxide neutralization

OH- + H2CO3 -> HCO3- + H2O

How does the respiratory system regulate pH?

Increased breathing rate eliminates acid (H+) in the lungs. Eliminating CO2 favors the forward reaction. (the on to the right)

H+ + HCO3- -> H2CO3 -> H2O + CO2

How to the kidneys regulate blood pH

The kidneys reabsorb HCO3- and excrete H+ as needed to increase pH. They also excrete ammonia as ammonium, which removes H+ to increase pH.

Structures associated with transporting blood to and from the kidney

Renal artery, renal vein, aorta, inferior vena cava

Adrenal glands

A pair of endocrine glands that sit just above the kidneys and secrete hormones such as aldosterone

Kidney

Organ that removes urea, excess water, and other waste products from the blood and passes them to the ureter

Ureters

Organ that carries urine from the kidneys to the bladder

Urinary bladder

Organ that stores urine until it can be excreted.

3 openings: 2 for the ureters and 1 for the urethra

Layer of epithelium allows bladder to stretch

Small folds of bladder mucosa act as valve to prevent backflow of urine into ureter

Urethra

Organ that passes urine to the outside of the body

3 regions of the kidney

Renal cortex, renal medulla, renal pelvis

Renal cortex

Outer layer of the kidney that dips down in between the renal medulla

Renal medulla

Inner portion of the kidney that consists of cone-shaped tissue masses called renal pyramids

Renal pelvis

Central space of the kidney that is continuous with with the ureter

Nephron

Functional unit of the kidney that filters blood and produce urine. It empties into one collecting duct, which empties into the renal pelvis

Collecting ducts

Last part of tubule, which receives filtrate from many nephrons; selectively reabsorbs water & ions (may secrete ions); delivers urine to calyxes and then renal pelvis. Give renal pyramids their striped appearance

Glomerular capsule (part o f nephron)

Enclosing structure surrounding each glomerulus, which contains pores (podocytes) that allow molecules from the blood to filter into the glomerular capsule

Steps in filtration

1. Glomerular filtration

2. Tubular reabsorption

3. Tubular secretion

Podocytes (podo: foot)

Cells that wrap around the capillaries of the glomerulus, facilitating filtration

Glomerular filtration

Water, salts, nutrient molecules move from glomerulus into the glomerular capsule

What should not be found in the urine?

Cells and large proteins

Proteinuria

proteins in the urine (mostly albumin)

What does a blood test measure?

Creatinine

What does a urine test measure?

Albumin

What is the measurement of glomerular filtrqtion rate used for?

to determine kidney function

Tubular reabsorption

Nutrient and salt molecules are reabsorbed from the nephron into the blood (capillaries around the nephron)

Tubular secretion

Certain ions and molecules (H+, creatinine, and penicillin) are actively secreted from the capillary network into the convoluted tubules. Some molecules that did not get eliminated during glomerular filtration pass to urine during this step.

Proteinuria

Presence of protein in urine (mostly albumins). Indicative of kidney malfunction.

How to measure glomerular filtration rate (assess kidney function)

Blood test: measures creatinine

Urine test: measures albumin

Proximal convoluted tubule

First section of the renal tubule that the blood flows through; reabsorbs water, ions (Na+), and all organic nutrients (glucose). Cells have many microvilli that increase SA

Diabetes mellitus

A disease in which the body's ability to produce or respond to the hormone insulin is impaired, resulting in abnormal metabolism of carbohydrates and elevated levels of glucose in the blood and urine.

Distal convoluted tube

Center for ion exchange between the blood and renal tube. Distal of several nephrons enter one collecting duct, which carries urine into the renal pelvis

Reabsorption rates of water, sodium, and glucose

Water: 99%

Sodium: 99.5%

Glucose: 100%

Urea: 44%

Layers of the ureters

Inner mucosa, smooth muscle later, outer fibrous coat of connective tissue

How does the ureters carry urine to the bladder?

Peristaltic contractions

Urination process

2 sphincters:

- Internal sphincter: smooth muscle, contracts/relaxes involuntarily

- External sphincter: skeletal muscle, contracts/relaxes voluntarily

When bladder fills, stretch receptors send sensory nerve signals. Motor nerves from spinal cord signal bladder to contract (sphincters relax)

Compare and contrast male and female urinary systems

Female: shorter urethra, greater susceptibility to UTIs. Not connected to reproductive system.

Males: urethra encircled by prostate gland, which sometimes enlarges, restricting urine flow. Connected to reproductive system; urethra carries urine during urination and sperm during ejaculation

Molecules that should NOT be found in urine

Glucose, ketones, blood (white blood cells), too many bacteria, crystals

Regulation of urine production is dependent on:

Blood volume

Factors regulating blood volume

Intense exercise (heavy sweating), water/salt consumption during meals, bleeding, hormones

Aldosterone

Hormone secreted by the adrenal gland that stimulates the kidney to retain sodium ions and water

Renin

An enzyme released by the kidney that creates angiotensin, a hormone that works to increase blood pressure by stimulating blood vessel constriction and the release of aldosterone

Angiotensin

Hormone that stimulates vasoconstriction and the release of aldosterone, a hormone that promotes sodium retention

ADH

Hormone produced by the brain. Responds to blood osmolarity (increases water reabsorption)

Atrial natriuretic hormone

Hormone produced by the heart. Promotes water/sodium excretion when too much blood (natrium = sodium)

EPO

Erythropoietin. Hormone produced by the kidney that promotes the growth of red blood cells

Diuretic definiton

A substance that promotes urination

Diuretic examples

Alcohol: inhibits secretion of ADH

Caffeine: increases rate of glomerular filtration and decreases tubular reabsorption of Na+

BP drugs: decrease tubular reabsorption of Na+ followed by decrease in water reabsorption and blood volume/pressure

Kidney stones

Solid crystalline masses formed in the kidney, resulting from an excess of insoluble salts or uric acid crystallizing in the urine; may become trapped anywhere along the urinary tract.

Edema

Swelling caused by too much fluid trapped in body's tissues

Dialysis

The separation of particles in a liquid on the basis of differences in their ability to pass through a membrane.

Hemodialysis

A treatment that removes waste from a person's blood by passing it through an artificial kidney (filtration system). The artificial kidney can add or extract substances from blood depending on the concentration of solutes in the blood and dialysis solution.

Vitamin D activation

Kidneys receive modified vitamin D2 and D3 from liver and convert it to the biologically active form

Why do diabetics urinate more frequently?

Decreased ability of cells to take up glucose leads to high glucose and therefore water in the urine. Triggers thirst and the consumption of more water.