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In the absence of the implantation of a fertilized embryo, the menstrual phase of the uterine cycle is initiated by the degeneration of the ________.
Corpus luteum
Pyloric Sphincter
- Controls the release of chyme into the small intestine
- At bottom of stomach right before small intestine
Nephron
- Functional unit of the kidney
- Smallest unit that can perform all kidney functions
- 1 million in each kidney
- Each nephron has two components (secretion and absorption): the vascular and tubular
Vascular component
Delivering blood that needs to be filtered
Tubular component
water and sodium moving in and out
Kidney overview
- Regulate H20 balance
- Regulate electrolyte balance
- Help maintain proper acid base
- Eliminating the waste of bodily metabolism
- Excreting foreign compounds
- Gluconeogensis
Kidneys function
Excretion, secretion and filtration
Renal Corpuscle
Initial filtering component in kidney; Forms filtrate
Filtrate
Formed in the renal corpuscle; Similar to plasma except protein-free
Parts of the kidney
Outer: Renal medulla: Cone shaped masses of tissue that secrete urine into tiny sac like tubules
Inner: Renal Pelvis: Funnel shaped tube surrounded by smooth muscle that uses peristalsis to move urine out of the kidney and into the ureter and bladder
Tubule
Extends from corpuscle; Can add and remove filtrate
Parts of the Renal Corpuscle
-Afferent arteriole
-Glomerulus
-Efferent arteriole
-Bowman's capsule
Glomerulus
Capillary bed in the renal corpuscle that filters blood
Components of renal Tubule
A continuous tube
-Proximal tubule
-Loop of Henle
-Distal tubule
-Collecting duct or tubule
Renal Process
1. Glomerular filtration
2. Tubular reabsorption
3. Tubular secretion
4.Excretion
Glomerular filtration
Formation of plasma filtrate during the renal process
Tubular reabsorption
Transport out of the tubular lumen during the renal process.
1. Diffusion: Substances move passively due to concentration gradients.
2. Mediated Transport: Active transport processes, often coupled with sodium (Na+) reabsorption, help reabsorb glucose and amino acids using Na+-dependent secondary active transport.
However, this process is limited by transporter saturation (Tm), meaning if too much of a substance (e.g., glucose) is present, not all can be reabsorbed.
Tubular secretion
Process:
- Diffusion: down concentration gradient
- Transcellular transport
Kidney tubules can selectively add some substances to the substances already filtered
Most important substances secreted by the tubules
1. H+ (Hydrogen Ions):
• Helps keep the body’s acid levels (pH) balanced.
2. K+ (Potassium):
• Keeps potassium levels low in the blood.
• Too much potassium messes up cells and nerves, which can be dangerous.
3. Organic Ions:
• Gets rid of weird stuff in your body, like antibiotics or other foreign chemicals.
The tubules are like the body’s cleanup crew, making sure acid, potassium, and foreign junk stay balanced and don’t cause problems.
Amount Excreted
= Amount filtered + Amount secreted - Amount reabsorbable
Glomerular layers
-Glomerular capillary endothelium
-Basement membrane
-Podocytes
Podocytes
-Encircle the glomerulus
-Slit diaphragm between foot processes
Glomerular filtration forces
- Capillary hydrostatic pressure
- Hydrostatic pressure in bowman's space
- Osmotic force of protein capillary
-Osmotic force of Bowman's space
GFR (Glomerular Filtration Rate)
Volume of fluid filtered from glomeruli into Bowman's space/unit of time; Regulated by SNS
Transepithelial
Tubular Reabsorption involves __________ transport.
Mediated Transport
Transport Coupled with Na+ reabsorption (Across not between)
Renal Clearance
When the kidneys remove excess ions and wastes from blood, thus the blood is "cleared" of a substance
Water intake
-Food
-Liquids
-Metabolism
Water output
-Sweat
-Urine
-Feces
-Insensible loss
Renal clearance
Kidneys remove excess ions and wastes from blood, thus the blood is "cleared" of a substance; how much we are taking from blood and how much is excreted out of the body
Total body balance of water
Water intake= food, liquids and metabolism
water output: Sweat, urine, when you breath
THE MAJOR HOMEOSTATIC CONTROL POINT FOR MAINTAINING BALANCE+ URINE LOSS
Na+ excretion
= Na+ filtered - Na+ reabsorbed
Baroreceptors
Sense Na+ in the blood based on blood volume
Sodium Regulation by baroreceptors
-Low Na levels due to diarrhea
-Low plasma volume
-Low BP
-Decrease firing of baroreceptors
-Increase activity of SNS
-Initiate changes in renal arterioles
-Lower GFR
-Decrease Na excreted
Arteriolar vasoconstriction
Decreases the GFR
RAAS
-Stimulates Na+ reabsorption
-Stimulates K+ secretion
-Acts on collecting duct
-Renin Angiotensin System (RAS) controls aldosterone secretion
RAAS sequence
1. Trigger:
• A drop in blood pressure or fluid volume signals the body to activate the RAS.
2. Renin Release:
• The kidney releases renin into the bloodstream.
3. Angiotensinogen to Angiotensin I:
• Renin converts a protein called angiotensinogen (produced by the liver) into angiotensin I.
4. ACE Converts Angiotensin I to Angiotensin II:
• Angiotensin-converting enzyme (ACE), released from the lungs, converts angiotensin I into angiotensin II.
5. Actions of Angiotensin II:
• Vasoconstriction: Angiotensin II causes blood vessels to narrow, increasing blood pressure.
• Adrenal Gland Activation: Angiotensin II stimulates the adrenal gland to release aldosterone.
6. Aldosterone’s Effect on the Kidneys:
• Aldosterone acts on the kidneys, promoting the reabsorption of salt (NaCl) and water (H₂O). This increases blood volume and pressure.
Renin
Released by Juxtaglomerular Cells; Controlled by SNS, Intrarenal baroreceptors, Na+ in filtrate
Osmoreceptors
Found in the hypothalamus; Sensitive to osmolarity; Increase in firing causes increased ADH
Descending limb
The limb of the loop henle that carries fluid from the cortex towards the medulla of the kidney and it gets saltier as water is being sucked out into the medulla becasue it is very salty
ADH
Acts to insert aquaporins into distal collecting duct
Ascending limb
The proximal tubule is only permeable to sodium so it can flow out and become less salty
Dehydration
Causes the secretion of ADH
acid-base balance
- Kidneys maintain blood pH by reabsorbing bicarbonate and secreting H+.
-Proximal tubule uses NA+/H+ pumps to exchange Na+ out and H+ in.
Micturition
- Urine stored in body is eliminated by micturtion.
- Urine in bladder stimulates stretch receptors
Micturition reflex
A bladder-to-bladder contraction reflex for which the reflex center is located in the rostral pontine tegmentum; When the bladder stretches due to too much bladder
GI Tract anatomy
Composed of:
-Mucosa
-Submucosa
-Muscularis Externa
-Adventia
Digestive tract consists of ?
Mouth, Pharynx, Esophagus, Stomach, small intestine (duodenum, Jejunum, Ileum), Large intestine (colon), Anus
Esophagus
- Two esophageal sphincter
Importance
- Stomach is very acidic don't want substance moving backwards into the sensitive tissue
-Gastric reflux is due to sphincter relaxed and not closing off like it should which allows stomach content into esophagus
-peristaltic waves push food through esophagus
Accessory digestive organs
- Salivary glands
- Exocrine pancreas
-Biliary system: (Liver, Gallbladder)
Tongue
- Movements aid in chewing and swallowing
- Plays important tole in speech
- taste buds
four functions of digestive system
- Motility (movement)
- Secretion (release into lumen)
- Digestion (breakdown)
- Absorption (absorption broken down molecules)
3-5 days
Lifespan of GI tract cell lining
Salivary Amylase
Begins digestion of carbohydrates within the mouth
Bolus
A Moistened bulk of food that is formed in the mouth in preparation for travel through the esophagus
gastric emptying
- Amount of chyme in stomach is main factor that influences strength of contraction
-Bolus when enters esophagus, chyme when it enters stomach
Saliva
-Mucus provides lubrication
-Salivary amylase begins digestion of carbs
-Antibacterial
-Solvent for molecules that stimulate taste buds
-Helps keep mouth and teeth clean
Swallowing
Initiated when a bolus is forced in the rear of the mouth
Sphincters
Prevent back flow in the GI tract
Peristaltic
Type of waves that push food through the esophagus
Stomach secretions
-HCl
-Mucus
-Pepsin
-Gastrin
-Histamine
HCl
-Released by parietal cells
-Breaks down proteins such as pepsin
Pepsin
-Released by chief cells
-Secreted as pepsinogen before being cleaved by HCl
Gastrin
Hormone that effects gastric motility
Histamine
Released by Enterochromaffin-like Cells
Amount of chyme
The main factor that influences the strength of contraction in the stomach
Fat
Too much ____ in Duodenum delays gastric emptying
Acid
____ in duodenum inhibits emptying of acidic gastric contents until neutralization can be accomplished
Hypertonicity
Gastric emptying is inhibited when osmolarity of duodenal contest starts to rise
Distention
When too much chyme is in the duodenum which inhibits emptying of even more gastric contents
-small intestine inhibits gastric emptying
Small intestine
Where most digestion and absorption is performed; Made of:
-Duodenum
-Jejunum
-Ileum
Mixing in the stomach
Peristalsis
Maximize absorption
-Folds of intestine
-Villi
-Microvilli
Brush border enzymes — Microvilli
- Enzymes within cellular lining that contribute to breakdown of things.
- Enzymes embedded within Microvilli and can break molecule down further so you can absorb it
Pancreatic enzymes
-Lipase
-Amylase
-Protease
Brush-border enzymes
Complete digestion of carbohydrates and proteins:
-Peptidase
-Disaccharidases
Peptidases
Enzymes that break down peptides
Disaccharidases
Enzymes that break down sugars
Intestinal Stem cells
Create new epithelial cells in the intestines every couple of days
Large Intestine
Consists of:
-Colon
-Cecum
-Appendix
-Rectum
Movement through GI tract
- Substances do not move uniformly
- Materials do not leave in the same order they arrive.
- Total emptying of stomach = 4-5 hrs
- transit through colon= 30-40
Large intestine functions
- Does not have brush border Microvilli, doesn't not absorb nutrients
- Absorption of water
-Electrolyte absorption
- Formation and storage of fecal material
Sodium
Main electrolyte absorbed by the large intestine; Pulls water with it in order to solidify fecal matter
Microflora
The large intestine possess _________, a bacteria.
Liver
The largest metabolic organ; The first organ to receive absorbed nutrients from hepatic portal vein.
- Hepatic vein— drains the liver and goes back to heart
- Hepatic Artery — need to supply liver oxygen, heart to liver.
Removes bilirubin- byproduct of bile
- Jungus = yellowing of skin
Bile
- Made by liver
- stored and concentrated in gallbladder
-After meal, bile enters duodenum
Bile salts
- Made from cholesterol
- Fat emulsifier
- After participation in fat digestion and absorption, most are reabsorbed into the blood
Liver functions
-Detox
-Produce plasma proteins
-Removes bilirubin
-Stores nutrients
-Manifactures bile
Bilirubin
Pigment from dead RBCs that is removed by the liver.
Hepatocytes
Cells in the liver that make up the liver
Liver sinusoids
Specialized capillaries that found in the liver
Kupffer cells
Macrophages that "Hang out" in the liver; Protect against foreign cells
Bile
-Stored in gallbladder
-After meal, enters duodenum
-Made from cholesterol
-Fat emulsifier
SNS
Inhibits digestive motility and secretions
PNS
Habits digestive motility and secretions
Secretions
___________ are regulated by luminal stimuli.
Luminal stimuli
Receptors in the GI tract that regulate secretions
1) Mechanoreceptors= dissension of wall
2) osmoreceptors= osmolarity of chyme
3) Chemoreceptors= acidity of chyme
4) chyme concentration of digestive products: ( Monosaccharides, fatty acids, peptides
Types of reflexes
Short= intrinsic nerve plexuses
- Stimulus with lumen
- local, stimulating a stretch or chemical change, stimulates the effector (smooth muscle), gland will secrete a digestive hormone, contraction
Long= Same path but goes all the way to the brain, smells and bites prepare your body with contractions;
- Site of food, taste of food stimulates long reflex
- Brain stimulates pancreas, gallbladder (other accessory organs) contribute to digestion
Mechanoreceptors
Sense dissension of the GI tract
Osmoreceptors (GI tract)
Sense osmolarity of chyme in the GI tract