Lab 9 - Urinalysis

Given three processes to do with kidney actions in terms of excretion - which of these processes leads to more excretion?

Increased filtration will lead to more excretion because it is the first step in urine formation, and creates the initial urine volume; increased reabsorption or secretion would result in more substances returning to the bloodstream, rather than leading to more excretion.

Renal portal system

a specialized vascular pathway found in some animals, including reptiles, fish, and amphibians, that transports venous blood from the caudal (tail) part of the body directly to the kidneys, bypassing the heart before returning to the circulation

Renal Portal System Outline

Afferent Arterioles → Glomerulus → Efferent Arterioles → Peritubular Capillaries

What are the abnormalities detected by urinalysis?

presence of glucose, presence of protein, presence of casts, cells, crystals, etc…, very high or low pH, very high or low specific gravity

What is the functions of the kidney in terms of ionic balance?

regulates plasma osmolarity by modulating the amount of water, solutes, and electrolytes in the blood

Normal plasma sodium concentration

135-145 mMol/L

Hyponatremia

< 130mMol/L

Hypertremia

> 150mMol/L

Vasopressin

increases water reabsorption

Thirst

initiated by the hypothalamus; causes you to drink water

Aldosterone

increases Na+ reabsorption

Diuretics

helps eliminate excess fluid and sodium through increased urination

Cortex

outer layer of the kidney responsible for blood filtration and hormone production

Medulla

regulates concentration of the urine

Papilla

the entry point for the collecting ducts

Pelvis

acts as a central collecting area, funneling urine into the ureter

Calyx

the cavity in which urine collects before it flows into the urinary bladder

Capsule

protects the kidney from injury and provides structural support

Nephron

filters blood, reabsorbs necessary substances, and excretes waste products as urine

Ureter

transports urine from the kidney to the bladder

Renal Artery

supplies oxygenated blood to the kidneys

Renal Veins

transports filtered, deoxygenated blood away from the kidneys and back to the heart

Afferent Arteriole

delivers blood to the glomerulus for filtering in the kidney

Efferent Arteriole

carries filtered blood away from the glomerulus and into the peritubular capillaries 

Tubule

Reabsorbs essential substances back into the bloodstream and removes waste products and excess fluid from the urine

Peritubular capillaries

functions in reabsorption and secretion between the blood and the nephron tubule

Collecting duct

collects urine from the nephrons

Loop of Henle

reabsorbs water and Na+Cl- from the filtrate

Bowman’s Capsule

filters blood from the glomerular capillaries

Glomerulus

filter the blood, creating a filtrate that passes into the Bowman's capsule

Where in the kidney is water reabsorbed?

Loop of Henle

What is a Benedict's test used for?

To test for the presence of sugars in a urine sample

What is the purpose of a Biuret test?

To test for the presence of proteins in a urine sample

What are the four processes of the kidney?

1. Glomerular Filtration: blood is filtered at the glomerulus in the nephron

2. Tubular Reabsorption: essential substances are reabsorbed back into the bloodstream (water, glucose, ions)

3. Tubular Secretion: tubules secrete substances like excess ions and waste into the filtered fluid

4. Excretion: the final urine product is excreted from the body through the urethra