Chapter 41 - Animal Digestion

Alimentary Canal = "gut"

- 1-way tube

- Contains specialized compartments for digestion & absorption (Compartments protect from self-digestion)

Distinguish regions of the alimentary canal & accessory glands by function: digestion, secretion, or absorption

Alimentary canal:

- Esophagus: secretion

- Mouth: secretion

- Pharynx: secretion

- Stomach: secretion

- Intestines: absorption

Other organs: (gallbladder, liver, salivary glands, teeth, tongue, spleen: digestion

Specialized Compartments for Digestion & Function:

Mouth, Pharynx, Esophagus

- Mechanical & Chemical digestion

Stomach

- Mechanical & Chemical digestion

Duodenum (upper part of small intestine)

- Digests peptides, lipids, carbohydrates, nucleic acids

Name the digestive secretions released into the mouth, stomach, duodenum

Mouth (chew, swallow, move to stomach):

- Amylase (starch in mouth)

- Mucus (lubrication of mouth, pharynx, esophagus)

Stomach (Mix & Digest):

- HCl (denatures protein)

- Pepsin (enzyme that breaks down proteins)

- Mucus (protects & lubricates)

Duodenum:

- HCO3 (neutralizes stomach acid)

- Bile from Liver (emulsifies fats)

- Pancreatic Enzymes (proteases, lipases, & carbohydrase)

- Enzymes from Intestinal Epithelium

Name the source of each digestive secretion & state its function

Amylase

- digests carbs/starch & made in salivary glands and pancreas

Mucus

- protect the lining of the digestive tract from damage caused by stomach acid and digestive enzymes

HCL

- denatures proteins, activates pepsinogen (pepsin lowers the pH of the stomach and is made in parietal cells)

Pepsin

- breaks proteins down and is made in the stomach lining

HCO3

- neutralizes stomach acid protease and is made in the pancreas

Proteases

- help your body digest and absorb the protein produced from the pancreas

Lipases

- breaks down lipids into fatty acids and glycerol & is made in the pancreas

Carbohydrase

- breaking down carbohydrates

Bile

- emulsifies lipids and it is made in the liver

Main biomolecules in particular foods

- Carbohydrates

- Proteins

- Nucleic Acids

- Lipids

List types of biomolecules digested in each digestive compartment:

- Mouth

- Stomach

- Duodenum

Mouth:

- Carbohydrates

Stomach:

- Proteins

Duodenum:

- Peptides, lipids, Sugars

Small Intestine & Large Intestine

Small Intestine:

- Epithelial Function: exchange

- Jejunum and ileum absorb monosaccharides, fatty acids, monoglycerides, amino acids and water

Large Intestine:

- Main function: absorb water and vitamins

- Home to bacterial community (gut microbes)

List what is absorbed in each compartment, explain how absorption occurs for different molecules: water, glucose, amino acids, fats

Small Intestine:

- Water: small intestine takes in water naturally through tiny openings (like a sponge soaking up water)

- Glucose: "helpers" actively carry glucose into the body from the small intestine

- Amino Acids: more "helpers" carry amino acids from the small intestine into the body

- Fats: fats are broken down into small pieces, which then sneak into the body's cells and are rebuilt for transport

Large Intestine (Colon):

- Mainly helps with absorbing some water, salt, and certain vitamins

Relate structure of gastrovascular cavities & alimentary canals to variables in Fick's Law of Diffusion

Fick's Law of Diffusion tells us that the rate of diffusion (movement of substances) depends on several factors: surface area, concentration gradient, distance, and the permeability of the membrane.

- Gastrovascular Cavities: the limited surface area restricts the amount of absorption that can occur, making diffusion less efficient

- Alimentary Canals: the extensive surface area provided by the folded structures and specialized projections (villi and microvilli) enhances the efficiency of absorption (increased surface area allows for more effective nutrient absorption through the intestinal lining)

Structure of the intestinal lining

Folds in the intestinal wall

Villus

- finger-like projection of intestinal lining

-made of epithelial cells, connective tissue, capillaries, and lymph duct

Microvillus

- tiny finger-like projections of apical membrane of intestinal epithelial cells

- contains many transport proteins

How does the structure of the intestinal lining enhances surface area?

The structure of the intestinal lining enhances surface area through tiny finger-like protrusions called villi and even smaller hair-like extensions called microvilli.

These structures increase the surface area of the intestine (like the bristles on a brush) allowing for better absorption of nutrients.

Trace digestion & absorption of each component of a meal through the human digestive tract

Mouth:

- Digestion Begins: Chewing in the mouth breaks down food into smaller pieces

- Saliva contains amylase starts breaking down carbohydrates

Stomach:

- Stomach acid and enzymes continue to break down proteins into peptides.

- The stomach mechanically mixes the meal

Small Intestine (Duodenum):

- Bile and Pancreatic enter

- Carbohydrates are further broken down into glucose by amylase

- Fats are emulsified by bile and lipase breaks them down into fatty acids and glycerol

- Proteins are digested into amino acids by trypsin

- Nutrients are absorbed into the bloodstream through the intestinal lining

Small Intestine (Jejunum and Ileum):

- Most nutrient absorption occurs in the jejunum and ileum regions

- Villi and microvilli on the intestinal lining increase the surface area for absorption

Large Intestine (Colon):

- The large intestine absorbs water and electrolytes

Rectum and Anus:

- Indigestible and unabsorbed material, along with bacteria, is eliminated from the body as feces through the anus

Epithelium

- Sheet of cells lining body cavities and organs

- Produces secretions

- Provides barrier against injury, pathogens

- Mediates exchange with external environment

Explain the function of epithelia in each digestive compartment

Mouth and Esophagus:

- Protect from harm and start breaking down food

Stomach:

- Protect itself from stomach acid and enzymes (secretes mucus)

Small Intestine (Duodenum, Jejunum, and Ileum):

- Absorb nutrients from food (villi and microvilli increase the surface area for absorption of nutrients)

Large Intestine:

- Absorb water and prepare waste for removal

Tight Junctions

- Formed by proteins in the membranes of neighboring epithelial cells

- Make a continuous seal around epithelial cell

- Prevent contents of intestine from entering between cells

Explain the function of tight junctions in epithelia in relation to digestion & absorption

They stop bad stuff from getting inside our bodies and let the good stuff, like nutrients, pass through so our bodies can use them.

(Tight junctions are like security guards, allowing only the right things to go through and keeping the wrong things out in our digestive system)

Fick's Law of Diffusion

Explains how molecules move from one place to another

- Surface Area: A bigger surface area makes molecules move faster.

- Concentration Difference: If there's a lot of molecules in one place and fewer in another, they'll move from the crowded place to the emptier one.

- Distance: The shorter the distance the molecules have to travel, the faster they move.

Predict the effect of an increase or decrease in each variable in Fick's Law of Diffusion on nutrient & water absorption in the small intestine:

Qs=DA((C2-C2)/x)(t)

'A' increases = the larger surface area would increase diffusion rate'

'X' increase = thickness increase would decrease diffusion rate

Concentration difference increase = increase diffusion rate

Trace transfer of biomolecules from intestine into blood or lymph & into organs

In the small intestine, nutrients from our food are absorbed into the body

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Nutrients like glucose and amino acids go directly into the blood.

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Fats and fat-soluble vitamins first enter the lymphatic system.

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These nutrients then travel in our bloodstream to different body parts like the liver, muscles, and organs.

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Each part of our body uses these nutrients for energy and growth.

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Any extra or waste is either stored or removed from our body.