HBS 11 + 12

Urinary system role

• Filter and eliminate waste (blood is constantly filtered by kidneys)

• Maintain homeostasis

• Contributes to acid-base balance

kidneys: what is it, where is it

major excretory organ

in retroperitoneal location: under the muscles of back and behind parietal pleura

surrounded by heavy cushion of fat to keep in place

receive highest percent of total body blood flow per min

ureters

transport urine from kidneys to bladder

urinary bladder

temporary storage reservoir for urine

urethra

transports urine out of the body

rugae

folds in transitional epithelium

trigone

smooth muscle region of bladder, when stretched, bladder signals to brain it is time to empty

kidney function

1. regulated overall fluid volume in the body via urine formation

2. excrete waste and regulate concentration of many substances in blood

3. regulate blood pressure

4. secretes EPO to stimulate erythrocyte formation

5. also an endocrine organ by secreting aldosterone (blood pressure regulation) and sex hormones

kidney structure (macro level)

cortex

medulla

hilium: renal pelvis)

nephron functions

produces urine

1) filtration: filter water and dissolved substances from blood

2) reabsorption: recover most of the filtrate from tubules and return it to blood

3) secretion: moving substances from blood into tubule

excretion of substance= filtration - reabsorption + secretion

How nephron works

1. glomerulus: filtration

2. proximal tubule: reabsorb 65% of filtrate

3. loop of henle: reabsorb 25% of filtrate

4. distal tubules: reabsorb 5% of filtrate, secrete

5. collecting ducts: reabsorb 5% of filtrate, secrete

Filtration

Glomerulus: network of capillaries surrounded by Bowman Capsule

• blood enters and filtered from afferent arteriole

• blood leaves via efferent arteriole

• only small stuff gets filtered

Reabsorption

movement of substances out of the renal tubule and back to the blood

Most solutes are reabsorbed in the proximal tubule

additional ions and water reabsorbed later in Loop of Henle, distal tubule and collecting duct

Secretion

Secretion is the process of moving substances from the blood into the tubules

• Sometimes substances that were reabsorbed earlier in the nephron are secreted back into the tubules later

• Secretion also serves as a way to clear the blood of drugs or excess ions

• Nitrogenous waste (urea) and drugs are secreted into the lumen of the kidney (forming urine) in the proximal tubule

• Ammonia, Potassium, Hydrogen, and some drugs are secreted in the distal tubule and collecting duct

What is reabsorbed+ secreted in each part of the nephron

glucose, amino acids, and protein: ~99-100% reabsorbed in proximal tubule

urea: ~50% reabsorbed in proximal tubule, secreted back in loop of henle, reabsorbed again in collecting ducts (secretion due to regulating urine concentration)

sodium and water: most sodium and water reabsorbed in proximal tubule, then reabsorbed at lower rates later on, but if high water intake, some secretion of water

potassium reabsorption rates

Mostly reabsorbed in proximal tubule, until collecting ducts

depends on diet,

If low potassium intake, reabsorb most of it

If high potassium intake, some later secreted

Diuresis

increased production of urine

Osmolality

concentration of the solutes in the tubule (inside the lumen)

There is a linear relationship between osmolality and water reabsorption:

Increase in osmolality – solutes are more concentrated = water is reabsorbed

Decrease in osmolality – solutes are more diluted = water stays in the tubule

anti-diuretic hormone (ADH)/vasopressin

regulates water permeability (ability to reabsorb water) in collecting duct, usually when dehydrated

diabetes insipidus

don’t produce sufficient ADH, can’t reabsorb water —> pee all the time

Digestive System

• Digestion (break down) of food

• Absorption of nutrients

• Elimination of waste products

Digestive system major functions

1. Ingestion

2. Propulsion (peristalsis)

3. Mechanical digestion (segmentation)

4. Chemical digestion

5. Absorption

6. Defecation

Alimentary Canal

(digestive tract) long, winding, continuous tube, MAIN ORGANS

1) Mouth

2) Esophagus

3) Stomach (pancreas afterwards but not main)

4) Small intestine

5) Large intestine

6) anus

Accessory oragns

surround alimentary canal, not direct segment of tube

liver, gallbladder, pancreas, salivary glands, teeth, tongue

Mouth

ingestion (mechanical and chemical with teeth and saliva)

• roof of mouth (hard and soft palate)

• Uvula: prevent food from entering nasal cavity

• Frenulum: thin membrane attaching tongue to floor of mouth

salivary amylase

enzyme in saliva

Teeth

1. Incisors: front teeth for cutting

2. Canine (cuspids): pointed, pierce and tear food

3. Premolars (bicuspids): two points, saw food

4. Molars (tricuspids): grind food

deciduous teeth: baby teeth

bolus

food after mouth

Esophagus

• Connects the oral cavity with the stomach

• Thin, collapsible, muscular, mucus-lined tube

• Each end guarded by sphincter; valve-like rings keeping food moving in one direction (upper esophageal sphincter and lower esophageal sphincter)

• Food moves via peristalsis due to muscle contractions.

Heartburn/acid indigestion (GERD)

backflow of stomach acid into esophagus called gastroesophageal reflux disease or GERD

Combat GERD

1) avoid stimulating foods

2) antacids

3) H2 receptor antagonists blocks acids from being released

Stomach

• Sections: fundus, body and pylorus - mixing and acid secretion

• Secretions from cells: gastric juices (HCl and pepsin)

• 3 layers of smooth muscle

• Mucosal barrier protects the stomach: mucus protects stomach wall, damaged epithelial cells are quickly replenished

• Pyloric sphincter holds the chyme (semisolid mixture of partially digested food) in the stomach until protein digestion begins

Small Intestine

• Where most nutrient digestion takes place

• Absorption occurs to move nutrients from SI into blood

• Parts: duodenum, jejunum, ileum

• Enzymes and digestive juices of its own and from pancreas

• Gallbladder delivers bile salts to aid in digestion of fats

• 4 layers

Layers of small intestine

1. Mucosa – absorption + secretion; Villi, epithelial cells, microvilli

2. Submucosa –connective tissue; contains blood vessels and nerves

3. Muscularis – muscle; peristalsis moves food down tract, helps with mixing of digestive juices, contributes to mechanical digestion

4. Serosa – connective tissue in outermost layer

Ruggae

folds occur throughout the GI tract for high surface area for absorption

Liver

• Glycogen storage (excess glucose)

• Makes glucose (gluconeogenesis)

• Makes bile —> secrete to gallbladder that helps with fat digestion in SI

• Make plasma proteins (prothrombin, fibrinogen, albumin)

• Detoxifies

• Stores excess nutrients and vitamins

Liver disorders

fatty liver: when there is excess fat, sugar, or toxins in the body

Hepatitis – inflammation of the liver

Cirrhosis – scar tissue forms in the liver

Pancreas

Both an endocrine (glucagon/insulin) and exocrine organ (pancreatic juices)

exocrine gland secretes pancreatic juice (digestion and neutralization of stomach acid that enters the small intestine)

Large Intestine

complete digestion, absorb water, concentrate feces

Intestinal microbiome (bacteria) helps to break down undigested material releasing nutrients

Cells do not have microvilli: not much absorption

Appendix

next to junction of ileum and cecum

the appendix serves as a vital safe house for the intestinal microbiome

Digestion of carbohydrates

1. Salivary amylase (mouth) and pancreatic amylase (SI)—> disaccharides

2. Small Intestine enzymes (SI) —> monosaccharides

Digestion of proteins

1. Pepsin (stomach) —> polypeptides

2. Pancreatic enzymes and SI enzymes —> amino acids

Digestion of lipids/fats

1. Bile (SI via liver/gallbladder) —> emulsified lipid droplets

2. Pancreatic lipases (SI) —> glycerol and fatty acids

Metabolism

sum total of all the chemical activities occurring in the cell

• Anabolism: synthesis of large molecules from small ones (takes energy)

• Catabolism: break down of complex structures to simpler ones (makes energy)

Digestion is anabolism or catabolism

catabolism which explains why digestion creates ATP

---

____ are main energy source, then ____, then ____

carbs, lipids, proteins

cells of juxtaglomerular apparatus are very important in

regulating blood pressure

when blood pressure is low

juxtaglomerular cells secrete renin that increases blood pressure via Renin-angiotensin- aldosterone system (RAAS) by constricting blood vessels and increasing sodium reabsorption