Digestive System Flashcards (Lec 16 Physio)

The stuff we eat must be what in order for our body to use?

Most nutrients we eat have to broken down into smaller components.

What does the Digestive System do?

It’s a disassembly line.

- It breaks nutrients down into a usable form

• It absorbs them so they can distributed to our tissues

• Eliminate waste also!

What are the 6 steps of digestion?

1. Ingestion

2. Propulsion

3. Digestion

4. Absorption

5. Compaction

6. Defecation

What is Ingestion?

It’s the first step.

It is selective food intake.

What is Propulsion?

The second step.

Movement of food through the GI tract.

What is Digestion?

The third step.

Mechanical and Chemical Breakdown of Food.

What is Absorption?

Fourth step.

Uptake of nutrient molecules into cells of Gi tract then into blood and lymph.

What is Compaction?

Fifth step.

Absorption of water and consolidation of indigestible residue into feces.

What is Defecation

The Sixth step.

Eliminates Feces.

What is Mechanical Digestion? Be very specific.

It’s the physical breakdown of food into smaller particles.

Cutting and Grinding of teeth.

How can we expose food surface to digestive enzymes? What digestion is this from; Chemical or Mechanical?

Churning of the stomach and small intestine (segmentation) helps to expose food surfaces to digestive enzymes.

Part of Mechanical Digestion

What is Chemical Digestion? Be specific.

It’s where a series of hydrolysis reactions help break macromolecules into monomers.
It all due to the action of digestive enzymes of salivary glands, stomach, pancreas and small intestine.

What are the results of Chemical Digestion?

Polysaccharides turn into monosaccharides
Proteins turn into amino acids

Fats into monoglycerides and fatty acids
Nucleic Acids turn into nucleotides.

What are the organs involved in Mechanical Digestion?

Chewing → Mouth

Churning → Stomach

Segmentation → Small Intestine

Saliva is produced where?

It produced in the Intrinsic Salivary Glands and Extrinsic Salivary Glands

Intrinsic Salivary Glands

• Scattered Throughout the Mouth

Extrinsic Salivary Glands

• Parotid

• Sublingual

• Submandibular

Which gland is the most active to keep the mouth moist?

Intrinsic Glands

When do Extrinsic become activated? And How?

It activates when food enters the mouth.

The mechanoreceptor and chemoreceptor triggers the salivatory nuclei (in the medulla oblongata) to activate the glands.

What is saliva composed of?

Its a hypotonic solution of 99% water.

It also contains..

• Salivary Amylase

• Lingual Lipase

• Mucin

• Lysozyme Enzyme

• Immunoglobulin

• Electrolytes

What does Salivary Amylase do?

Helps with starch digestion

What does Lingual Lipase do?

Digests fat in the stomach.

What does Mucin do?

Combines with water to form mucus. It also binds and lubricates food.

What does Lysozyme do

An enzyme that kills Bacteria.

What does Immunoglobulin A do in saliva?

Inhibits bacterial growth.

What are in Electrolytes for saliva?

Composed of Na+, K+, and Cl- Phosphate and Bicarbonate.

What is the normal pH for saliva?

6.8-7.0

In swallowing, it involves coordination in how many muscles?

Involves coordination among 22 separate muscles of the upper GI tract.

There are 2 phases pf swallowing. What are they?

Buccal phase and Pharyngoesophageal phase.

What is the Buccal Phase?

The voluntary phase that occurs in the mouth. The tongue presses against the hard palate to force food into the oropharynx.

What is the Pharyngealesophageal phase?

The involuntary phase.. Its initiated when food enters the oropharynx.
Its controlled by swallowing center in the brain stem.

During the Pharyngealesophageal phase, why is Respiration temporarily inhibited?

Its inhibited because its routes are blocked by the uvula, tongue and epiglottis.

How does food get into the esophagus?

The upper esophageal sphincter relaxes letting food into the esophagus.

Continued of the Pharyngealesophageal phase..? What else occurs

So the descending wave of peristalysis pushes food into the stomach.
Approximately 8 seconds for solid food.

The sphincter muscle closes behind food to prevent regurgitation.

What is the stomach?

It functions as the food storage organ.

It can stretch to 4 L and extend to the pelvis.
- 50 ML when it’s empty.

What does the stomach specifically do?

It mechanically breaks up food particles and liquefy food to make a soupy mixture. (CHYME!!)

What does the stomach contain? Secretes??

It contains gastric glands that secretes a variety of molecules aiding in digestion.

What does the Mucous Neck Cells, Parietal Cells, and Chief Cells do in the stomach?

Mucous Neck Cells → Secretes Mucus
Parietal Cells → Secretes Hydrochloric Acid
Chief Cells → Secretes gastric lipase and pepsinogen

What is HCI?

Hydrochloric Acid..
Its mainly produced by parietal cells.

• Lower gastric pH to as low as 0.8

• It activates pepsin and lingual lipase

• Destroys INGESTED PATHOGENS!!

What is the production of Hydrochloric Acid? How does it start?

1. Blood is delivers CO2 to the parietal cells.

2. The parietal cells react with CO2 and water. → To make carbonic Acid which then dissociates to bicarbonate and H+
   (CO2 +H2O → H2CO3 → HCO3- + H+)

3. H+ is then pumped into the gastric gland lumen where it then combines with Cl- to make HCI..!!!

What is the inactive form of the enzyme called pepsin?

Pepsinogen is the inactive form.

Pepsinogen is produced by what type of cells?

Chief Cells

How does Pepsinogen convert to Pepsin?

HCI converts pepsinogen into pepsin..by removing some of its amino acids.

What enzyme is critical for chemical digestion of proteins in the stomach?

Pepsin..

What is Gastric Lipase?

It’s produced by chief cells.

Both gastric lipase and lingual lipase play a minor role in digesting dietary fats..

It digests about 10%-15% of dietary fats in the stomach.
Rest digested in the small intestine!

What triggers stomach to relax to receive food?

Swallowing center triggers it to relax and receive food.

What does the stomach undergo?

Undergoes rhythmic peristaltic contractions..

- To churn food, it mixes with gastric juices and promotes mechanical and chemical digestion.

How many ml of chyme squirts into the duodenum?

3 ml of chyme squirts into the duodenum.

Usually how many hours does a meal empty out from the stomach..?

4 hours..

What nutrient is primarily digested in the stomach..?

Proteins

Starch and Fat digestion occurs???

To a lesser extent.

What statement describes nutrient absorption in the stomach?

There is no significant amount of nutrients is absorbed.

What substance can be absorbed in the stomach?

Aspirin and Lipid Soluble drugs.

Where is alcohol mainly absorbed in? However, the intoxicating effects of alcohol depend on what?

Small intestine..

It depends on the speed of stomach emptying.

What are the three phases of Gastric Activity..?

• Cephalic Phase → Stomach being controlled by the brain

• Gastric Phase → Stomach controlling itself

• Intestinal Phase → Stomach is controlled by the small Intestine.

Keep in mind these phases overlap and can occur simultaneously.

Specifically what is the Cephalic Phase?

The stomach responds to the site, smell, taste, or though of food.

The sensory and mental inputs triggers hypothalamus to relay signals to medulla oblongata.

In turn, the brain stimulates gastric secretions in the stomach.

Specifically what is the Gastric Phase?

The swallowed food and semi-digested protein activates the gastric glands.

Gastrin (G cells) and Histamine (by ECL cells) are secreted by gastric glands.

Two thirds of gastric secretion occurs in this phase.