Exam Review and Digestion Notes

Exam 3 Review

• Exam review recap.
• Volume through the glomerulus and urine formation.
• Filtration process reminder: Modification is possible until the collecting duct.

Fluid Regulation

• Kidneys help with fluid loss (vomiting, diarrhea, hemorrhage) and excess fluid.
• Water intoxication can lead to brain swelling and death.
• Maintaining homeostasis:
  • What I lose, I need to replace.
  • Excess intake is excreted.
  • Avoid excessive water intake.

Fluid Volume

• Fluid gain:
  • Excess water lost through lungs, skin, and kidneys.
  • Kidneys help regulate excess water.
• Fluid loss:
  • Impacts filtration in nephrons.
  • Essential to maintain balance for filtration and urine formation.

Water Conservation

• Regardless of dehydration, some water always lost in urine.
• Waste products require water for excretion.
• Hormone involved: Vasopressin
  • Vasopressin regulates water channels (aquaporins) in the collecting duct and distal tubule.
  • Vasopressin helps conserve water, but cannot replace losses entirely.

Kidney's Role in pH Regulation

• Regulates bicarbonate reuptake and hydrogen ion excretion.
• Filters significant bicarbonate daily (equivalent to about a pound of baking soda).

Bicarbonate and Hydrogen Ion Movement

• Diagram Explanation:
  • Lumen (filtrate), cell, and blood compartments.
  • Bicarbonate reacts with hydrogen ion to produce water and $CO_2$ in the lumen.
  • $CO_2$ diffuses into the cell.
  • Carbonic anhydrase reaction: $CO<em>2 + H</em>2O \rightleftharpoons H^+ + HCO_3^-$
  • Bicarbonate moves into the blood; hydrogen ion moves into the filtrate (sodium coming in).
  • Bicarbonate reclaimed from filtrate indirectly.

Acidosis

• Acidic environment in filtrate (high hydrogen ion concentration) interacts with bicarbonate, acting as a buffer.
• $CO_2$ moves into the cell; carbonic anhydrase reaction produces hydrogen ion and bicarbonate.
• Bicarbonate sent back into the blood to interact with excess hydrogen.
• Hydrogen ion is removed into the urine.

Alkalosis

• Goal: to make the blood more acidic.
• Hydrogen ion moves from the cell into the blood, and bicarbonate moves into the urine.
• Hydrogen goes in, potassium moves out maintain balance.

Lungs Role in pH Regulation

• Regulate pH through ventilation (depth and rate).
• Blow off $CO_2$ and take in oxygen.
• $CO_2$ = a volatile acid transfer (due to carbonic anhydrase reaction).
• Lungs provide faster pH regulation compared to kidneys

Volume and Osmolarity

• These are the conditions to consider
  • Volume
  • Osmolarity
  • Decrease
  • Increase
  • No change
• Changes with volume and osmolarity.

Digestion Introduction

• Primary consumers (herbivores) at the base of the food pyramid.
• Plants contain much energy, but difficult to digest; need symbiotic relationships with bacteria or protozoa to break down cell walls due to lack of cellulase.
• Carnivores eat herbivores/carnivores (secondary or higher consumers).
  • Methods: capturing prey alive, eating dead prey, constriction, paralysis using venoms.
  • Shorter digestive tracts than herbivores due to easier breakdown of animal material.
  • Cecum is also shorter.
• Omnivores eat plants and animals; can be at any level of the pyramid.

Feeding Mechanisms

• Filter feeders: remove suspended particles from water or air.
• Substrate feeders: consume the medium in which they are living for example earthworms.
• Fluid feeders: consume fluids, example mosquitos.
• Bulk feeders: eat large pieces of food.

Food Processing

• Acquisition of food.
  • Prehension: getting food to the mouth (e.g., using hands, trunk, or lips).
• Ingestion: taking food into the mouth and digestive tract.
• Digestion: breaking down food.
  • Absorption and secretion occur.
• Egestion/Elimination: removal of indigestible material or waste.

Digestion Types

• Intracellular digestion:
  • Enzymes function inside the cell.
  • Examples: sponges and paramecium.
• Extracellular digestion:
  • Enzymes released into the lumen of the digestive tract (mouth, stomach, intestine).

Gastrovascular Cavities

• Incomplete digestive tract with one opening. * Waste exits through the same opening.
  • Examples: planarians and cnidarians.

Complete Digestive Tracts

• Possess a mouth and an anus.
• Advantage: continuous eating and processing possible.

Digestive Tract Structure

• Vertebrate vs. invertebrate digestive tracts:
  • Basic scheme is similar: mouth, esophagus, stomach, intestine, anus.
  • Vertebrates lack crop and gizzard; stomach handles grinding and storage.

Accessory Structures

• Connect to the digestive tract via a duct (e.g., pancreas, salivary glands).
• Modified projections (teeth, tongue).

Species Differences

• Pharynx: Connection to thyroid and digestive system.
  • Longer in animals with gills compared to lungs.
  • Dogs have longer pharynx due to distance between larynx and mouth entry point.
• Herbivores: Llonger digestive tract and larger cecum compared to carnivores.
• Teeth: Type of teeth is consistent but number and size can vary.
• Stomach: Single-chambered stomachs (like ours) vs. multi-chambered stomachs (ruminants).
• Gallbladder: Present in some animals, absent in rats.

Teeth Structure

• Incisors: biting and nipping.
• Canines: piercing.
• Premolars and molars: grinding and crushing.

Food Sources

• Plant
• Animal
• Both plant and animal.

Breakdown Types

• Mechanical breakdown.
• Chemical breakdown.
• Enzymatic breakdown.

Digestive System- Overview

• Salivary glands, teeth, tongue (accessory structures).
• Pharynx.
• Esophagus (level of the marinus).
• Stomach (accessory structures: pancreas, gallbladder, liver).
• Small intestine.
• Large intestine (ascending, transverse, descending, rectum).
• Cecum (remnant of longer structure in herbivores).
• Appendix (appendicitis pain on right side).

Salivary Glands

• Enzymatic digestion starts in the mouth (amylase and lipase).
  • Amylase works on starches
  • Lipase works on fats.
• Lingual lipase prefers the acidic environment of the stomach.
• Amylase initiates starch breakdown in the mouth.
• Salivary Gland Locations:
  • Parotid gland.
  • Submandibular (under mandible).
  • Sublingual (under tongue).

Swallowing

• Voluntary vs. Involuntary.
  • Voluntary: Get to the back of the mouth.
  • Involuntary: To begin it
• Upper and lower sphincter muscles regulate entry to esophagus.
• Pressure opens up the sphincter
  • Gradients.
    Glottis
    *Close off airway.
    Bolus
    *Bolus of food that we get back there will be swallowed.

Stomach-Digestion Breakdown

• Limited enzymatic.
• Contraction.
• Chemical (HCl acid environment).
• Enzymatic - not a full mixture of enzymes here to break down proteins and what works of fat until that lipase loses its activity.
• Most bulk happens in intestinal tract. Regulate the entrance *55 or 50ml release regulated by pyloric sphincter
  • We add that to intestines and enzymes going before next batch is made.
    *Three layers of muscle wall.
    *Reggae are folds.

Stomach

• Wall structure: three layers of muscle, folds (rugae) to expand.
  • 50ML empty to 1 liter empty.
• Layers
  *All three in all three layers.

Stomach Epithelium

• Pits containing different cells.
• Mucus cells:
  • Secrete mucus.
• Parietal cells:
  *Secrete HCl (acid secretion).
  *Intrinsic factor help to absorb B12
• Chief cells:
  • Secrete pepsinogen (inactive pepsin).
    • Pepsinogen activated by acid; breaks down protein. The acidic environment is also helpful in converting pepsinogen to pepsin.

Gastric Glands.

• Carbonic anhydrase:
  • Hydrogen pumped into lumen; chloride follows.
  • Bicarbonate goes into the blood gradient with chloride (alkaline tide after eating).

Stomach Digestion Phases

• Cephalic phase (head):
  • Stimulation via senses (hearing, seeing, smelling food).
    *Gastric juice.
• Gastrin Phase. *D cells source of hormone is somatostatin
  • Somatostatin, its role is to inhibit gastric release.