Overview of the Urinary and Digestive Systems

What are the primary functions of the urinary system?

Excretion of organic waste, elimination of waste products, and homeostatic regulation of blood plasma.

What is the role of the kidneys in the urinary system?

The kidneys produce urine.

What structures are involved in the storage and discharge of urine?

The ureters transport urine to the bladder, which stores urine, and the urethra discharges it.

What is the blood supply to the kidneys?

Renal arteries branch into segmental arteries, interlobar arteries, arcuate arteries, and interlobular arteries.

What are the components of the renal corpuscle?

The renal corpuscle consists of Bowman's Capsule and the Glomerulus.

Where is filtrate formed in the nephron?

Filtrate is formed in the glomerulus.

What are the parts of the renal tubule and their functions?

Proximal convoluted tubule (reabsorbs water, ions, and nutrients), Loop of Henle (further reabsorbs water, sodium, and chloride), Distal convoluted tubule (secretes ions, acids, drugs, and toxins).

What are the two types of nephrons and their locations?

Cortical nephrons (85% of all nephrons, located in the cortex) and Juxtamedullary nephrons (located closer to the renal medulla with loops extending deep into renal pyramids).

What is the primary function of the PCT in the nephron?

The PCT actively reabsorbs nutrients, plasma proteins, and ions into the filtrate.

What is the role of the Loop of Henle?

The Loop of Henle regulates water and salt reabsorption.

What is the significance of the glomerulus in urine formation?

The glomerulus allows for the filtration of blood, forming the initial filtrate.

What are the basic processes of urine formation?

Filtration, reabsorption, and secretion.

How does carrier-mediated transport affect kidney filtration?

It modifies filtration through facilitated diffusion, active transport, cotransport, and countertransport.

What is the Glomerular Filtration Rate (GFR)?

The amount of filtrate produced in the kidneys each minute.

What factors can alter filtration pressure and GFR?

Autoregulation, hormonal changes, and autonomic regulation.

What happens when there is a drop in filtration pressure?

The juxtaglomerular apparatus releases renin and erythropoietin.

What occurs during sympathetic activation in the kidneys?

It causes vasoconstriction of afferent arterioles, decreasing GFR and slowing filtrate production.

What percentage of the filtrate is reabsorbed by the PCT?

60-70% of the filtrate is reabsorbed in the PCT.

What substances are actively reabsorbed in the PCT?

Most organic nutrients and sodium.

What is the function of the DCT in the nephron?

The DCT performs the final adjustment of urine through active secretion and absorption.

What opposes glomerular hydrostatic pressure during filtration?

Capsular hydrostatic pressure and blood colloid osmotic pressure.

What is the net hydrostatic pressure formula?

Net hydrostatic pressure = Glomerular hydrostatic pressure - Capsular hydrostatic pressure.

What is the role of podocytes in the glomerulus?

Podocytes cover the lamina densa of capillaries and project into the capsular space, forming filtration slits.

What is the renal threshold?

The maximum concentration of a substance that can be reabsorbed by the kidneys.

What is the primary function of DCT in the kidneys?

DCT performs final adjustment of tubular fluid.

What ions are actively resorbed by tubular cells in the kidneys?

Sodium (Na) and Chloride (Cl) ions are actively resorbed in exchange for potassium and hydrogen ions.

How is water and solute loss regulated in the kidneys?

Water and solute loss is regulated by aldosterone and ADH (antidiuretic hormone).

What substances are reabsorbed in the kidneys?

Sodium ions, bicarbonate, and urea are resorbed.

How is pH controlled in the kidneys?

pH is controlled by the secretion of hydrogen or bicarbonate ions.

What does the composition of normal urine reflect?

It varies with metabolic and hormonal events and reflects filtration, absorption, and secretion activity of the nephrons.

What is urinalysis?

Urinalysis is the chemical and physical analysis of urine.

What is the primary function of the urinary bladder?

The urinary bladder serves as a reservoir for the storage of urine.

What muscle contraction voids the bladder?

Contraction of the detrusor muscle voids the bladder.

What are the internal features of the urinary bladder?

The internal features include the trigone, neck, internal urethral sphincter, and ruggae.

What initiates the micturition reflex?

The micturition reflex is initiated by stretch receptors in the wall of the bladder.

What is required for urination?

Urination requires coupling the micturition reflex with relaxation of the external urethral sphincter.

What are the main functions of the digestive system?

The main functions include ingestion, mechanical processing, digestion, absorption, secretion, and excretion.

What are mesenteries in the digestive system?

Mesenteries are sheets of serous membranes that support portions of the digestive tract.

What is the role of the greater omentum?

The greater omentum lies anterior to the abdominal viscera and provides padding, protection, insulation, and energy reserves.

What lines the digestive tract?

The mucosa lines the digestive tract and is moistened by glandular secretions.

What are the layers of the digestive tract?

The layers include the mucosa, submucosa, muscularis externa, and adventitia/serosa.

What is peristalsis?

Peristalsis is the wave-like contraction that moves a bolus through the digestive tract.

What is segmentation in the digestive system?

Segmentation is the process that churns and fragments a bolus.

What controls the movement of materials along the digestive tract?

Movement is controlled by neural mechanisms, hormonal mechanisms, and local mechanisms.

What are the three major salivary glands?

The three major salivary glands are the parotid, sublingual, and submandibular glands.

What is the primary function of saliva?

Saliva functions in lubrication, moistening, dissolving, and initiating digestion of complex carbohydrates.

What are the histological features of the esophagus?

The esophagus has nonkeratinized, stratified squamous epithelium, folded mucosa and submucosa, mucous secretion by esophageal glands, and a muscularis with both smooth and skeletal muscle portions.

What are the main functions of the stomach?

The stomach's functions include bulk storage of undigested food, mechanical breakdown of food, disruption of chemical bonds via acids and enzymes, and production of intrinsic factor.

What regulates gastric activity?

Gastric activity is regulated by the cephalic phase, gastric phase, and intestinal phase.

What controls the rate of gastric emptying during the intestinal phase?

The intestinal phase controls the rate of gastric emptying.

What is the duration of the intestinal phase?

The intestinal phase lasts for several hours.

What enzymes begin digestion in the oral cavity?

Salivary amylase (for carbohydrates) and lingual lipase (for lipids) begin digestion.

At what pH are salivary amylase and lingual lipase inactivated?

They are inactivated when the pH is less than 4.5.

What is the primary enzyme for protein digestion in the stomach?

Pepsin is the primary enzyme for protein digestion.

What is the extent of nutrient absorption in the stomach?

Very little absorption of nutrients occurs in the stomach; some drugs can be absorbed.

What are the three subdivisions of the small intestine?

The three subdivisions are the duodenum (25 cm), jejunum (2.5 m), and ileum (3.5 m).

What is the function of the ileocecal sphincter?

The ileocecal sphincter serves as a transition between the small and large intestine.

What are plicae in the small intestine?

Plicae are transverse folds of the intestinal lining.

What are villi and their function in the small intestine?

Villi are fingerlike projections of the mucosa that increase surface area for absorption.

What type of cells cover the villi?

Villi are covered by columnar epithelium with a brush border.

What are lacteals?

Lacteals are terminal lymphatics found in the villus.

What do intestinal juices do?

Intestinal juices moisten chyme, help buffer acids, maintain digestive material in solution, and liquify it.

What stimulates intestinal juices?

Intestinal juices are stimulated by the vagus nerve and inhibited by the sympathetic nervous system.

What is peristalsis?

Peristalsis is the movement of food down the digestive tract through contractions.

What is segmentation in the intestines?

Segmentation is the contraction of intestinal circular smooth muscles that mixes chyme.

What triggers the gastroenteric reflex?

The gastroenteric reflex is initiated by stretch receptors in the stomach.

What is the role of the pancreas in digestion?

The pancreas has both endocrine functions (insulin and glucagon) and exocrine functions (secreting pancreatic juice into the small intestine).

What does the liver produce?

The liver produces bile and performs metabolic and hematological regulation.

What is the function of the gallbladder?

The gallbladder stores, modifies, and concentrates bile.

What are the functions of the large intestine?

The large intestine reabsorbs water, compacts material into feces, absorbs vitamins produced by bacteria, and stores fecal matter.

What is the histological feature of the large intestine?

The large intestine lacks villi and has goblet cells and deep intestinal glands.

What is the defecation reflex triggered by?

The defecation reflex is triggered by the distention of rectal walls.

What is the role of bile salts in lipid digestion?

Bile salts improve chemical digestion by emulsifying lipid drops, forming micelles.

How are monosaccharides absorbed in the small intestine?

Monosaccharides are absorbed across the intestinal epithelium.

What happens to proteins during digestion in terms of structure?

Low pH destroys the tertiary and quaternary structure of proteins.

How is water absorbed in the digestive system?

Nearly all ingested water is reabsorbed via osmosis.