Ch 14 Digestive System

Digestive System

Chapter 14

Learning Objectives

1. Compare/contrast the 4 major macromolecules in terms of their function(s) in the body and the monomers they're made of. 2. Describe how the structure of an enzyme determines its function. 3. List the 4 functions of the digestive system and identify what digestive structure(s) carry out these functions. 4. Identify the structures of the alimentary canal v. accessory organs. 5. Explain how the endocrine system is integrated with the digestive system (hunger/satiety/blood glucose). 6. Explain the steps of aerobic cellular respiration to describe how cells convert glucose into ATP. 7. Identify the major digestive disorders discussed in class.

Vocab

• macromolecule
• monomer
• carbohydrate
• monosaccharide
• protein
• amino acid
• lipid
• glycerol & fatty acid
• nucleic acid
• nucleotide
• mechanical digestion
• chemical digestion
• enzymes
• catalyze
• substrate
• specificity
• denature
• ingestion
• digestion
• absorption
• elimination
• alimentary canal

• gastrointestinal tract
• oral cavity
• salivary glands
• soft palate
• tongue
• teeth
• pharynx

• esophagus
• glottis
• epiglottis
• stomach
• small intestine
• large intestine
• duodenum
• jejunum
• ileum
• cecum
• cardiac sphincter
• pyloric sphincter
• liver
• gallbladder
• bile duct
• pancreas
• anus

• appendix
• rectum
• amylase
• lipase
• stomach acid
• pepsin
• bile
• leptin
• ghrelin
• insulin
• glucagon
• hyperglycemia
• hypoglycemia
• cellular respiration
• ATP
• ADP
• glycolysis
• Kreb's cycle
• Electron Transport Chain
• NADH
• FADH2
• H+
• oxygen
• final electron acceptor

• ATP synthase
• phosphorylate
• type 1 diabetes
• type 2 diabetes
• GERD
• peptic ulcer
• gastroenteritis
• cholelithiasis
• diverticulitis
• inflammatory bowel disease
• autoimmune

Review: Macromolecules

What are the 4 major macromolecules?

What are their monomers (building blocks)?

• Carbohydrates > monosaccharides
• Proteins > amino acids
• Lipids > glycerol + fatty acid
• Nucleic acid > nucleotide

Review: Macromolecules

How do we break down macromolecules into their monomers (subunits/building blocks)?

Mechanical and chemical digestion!

Stomach churning & acid

Enzymes

Chewing

Review: Enzymes

Special proteins that catalyze reactions

1. Decreases energy needed for a reaction to proceed. 2. Provides a physical site for substrate(s) to bind and react

There are many enzymes in the digestive system - they are responsible for chemical digestion

Metabolism

Metabolism = all chemical reactions

Two types of metabolic reactions

Enzyme Rules

**Enzyme names usually end in "-ase"

• Enzymes can be reused for many reactions
• Enzymes are very specific to their substrate(s)

• Enzymes work best under optimal conditions
• Temperature:
• Too cold = reaction time will slow
• Too hot = enzyme will denature

• pH (acidity v. alkalinity)
• outside of optimal pH = enzyme denatures

Functions of Digestive System

Basic Anatomy of Digestive System

Accessory Organs

Alimentary Canal

vs.

• AKA gastrointestinal (GI) tract
• organs that food and waste travel through within the digestive system

• Examples:

• organs that perform essential digestive functions, but are not part of the alimentary canal (GI tract)

• Examples:

• Mouth
• Esophagus
• Stomach
• Small Intestine
• Large Intestine

• Teeth
• Tongue
• Pancreas
• Liver
• Gallbladder

Click on each structure to learn more.

Click on each structure to learn more.

Click on each structure to learn more.

Endocrine Control of the Digestive System

Hunger/Satiety

Blood Glucose Regulation

Once glucose is absorbed and sent to the cells, how is it used to make ATP?

Cellular Respiration!!!!

Glycolysis

Kreb's Cycle

Electron Transport Chain

But before we begin, what is ATP?

• Adenosine Triphosphate
• Macromolecule: nucleic acid

Aerobic Cellular Respiration

Goal: break glucose down to harvest energy needed to phosphorylate ADP to make ATP

• For every molecule of glucose that undergoes these reactions, _________ molecules of ATP can potentially be created.

• This process requires ______________.

3 Major Steps:

1. Glycolysis
2. Kreb's Cycle
3. Electron Transport Chain

Step 1: Glycolysis

Goal/Major product:

• Break down glucose >

2 pyruvate molecules It also generates:

• Small amount of ATP
• Small amount of NADH

Step 2: Kreb's Cycle

Goal:

• Oxidize pyruvate

Generates:

• Small amount of ATP
• LARGE amount of NADH & FADH2

Step 3: Electron Transport Chain

1. NADH and FADH2 transport their electrons to the ETC proteins. 2. Energy from electrons is used to transport H+ across membrane (against concentration gradient) Oxygen = final electron acceptor 3. H+ move through ATP synthase—> generates energy to phosphorylate ADP -> ATP

Digestive Diseases/Disorders

Diabetes

vs.

Type 1

Type 2

• Autoimmune disorder
• Body destroys pancreas -> pancreas cannot produce insulin
• Leads to increased blood glucose
• Always requires treatment with insulin.

• "Insulin Resistant Diabetes"
• Pancreas is functional and produces plenty of insulin
• Insulin receptors on cells lose sensitivity - insulin cannot bind to receptors > prevents glucose from entering the cells
• Leads to increased blood glucose
• Can sometimes be managed with diet/exercise
• May require meds like metformin (makes more receptors) or insulin

Gastroesophageal Reflux Disease (GERD)

Failure of ____________ sphincter allows stomach acid to regurgitate into ______________. Symptoms:

• Heartburn
• Sour/bitter taste
• Difficulty swallowing

Treatment:

• antacids

Peptic Ulcer

Caused by bacteria called ______________________. This bacteria damages the protective ________________ lining of the stomach which causes acid to "eat" into stomach tissue. Symptoms:

• pain
• feeling of fullness
• nausea/vomiting
• black stool

Treatment:

• antibiotics + antacids
• Surgery if perforation occurs

Inflammation of the ______________ & _________________ caused by a bacterial or viral infection. Signs/Symptoms:

• Fever
• excessive vomiting and/or diarrhea
• dehydration

Treatment:

• supportive care
• antibiotics - if caused by bacteria

Gastroenteritis

Cholelithiasis "Gallstones"

Hardened deposits of ____________ that can block the ____________ duct Signs/symptoms:

• Pain (especially after fatty meal)
• Nausea/vomiting

Treatment:

• Reduce fat-intake
• Surgery

Diverticulitis

Development of _______________ in large intestine that can become inflamed. Signs/Symptoms:

• Abdominal pain
• Sudden diarrhea and/or constipation
• Nausea
• Fever

Treatment

• liquid diet until symptoms resolve
• increase fiber
• surgery

Inflammatory Bowel Disease (IBD)

Autoimmune condition - body's immune system mistakenly __________ it's own normal intestine cells. This leads to ______________ (swelling) and ulcers to develop in the intestines. Signs/Symptoms:

• abdominal pain
• diarrhea
• mucus/blood in stool
• weight loss
• fatigue

Treatment:

• immune suppressants
• surgery

Salivary glands

Exocrine glands that produce & secrete saliva which: 1. moistens & dissolves food 2. Contains amylase (breaks down carbs)

Cecum

1st part of large intestine

Ileum

3rd & last part of small intestines. Nutrient absorption continues and finishes here- large amount of villi to aid in nutrient absorption

Ingestion

The process of taking in food/drink by swallowing it

Esophagus

Tube that carries bolus of food from pharynx to stomach. Made of smooth muscle - rings contract in wave-like pattern (peristalsis)

Epiglottis

• Flap of tissue above the glottis.

• When swallowing, it lowers over the glottis to prevent food from entering the respiratory tract.

Video of "pill stuck in throat"

Stomach

Muscular organ that continues mechanical & chemical digestion

• mechanical - churning
• chemical - stomach secretes the following:
• Stomach acid (hydrocholoric acid) - chemical digestion & kills microbes
• Pepsin - enzyme digests proteins

Lined with mucus membranes that secretes mucus to protect it from harsh stomach acid. When stomach acid mixes with the bolus of food, it becomes a watery substance that is now called chyme.

Bile Duct

transports bile from the gallbladder to the duodenum

Anus

Set of 2 sphincters (muscular rings) that regulate the release of feces from the rectum to your toilet during defecation. Internal sphincter - involuntary control. external sphincter - voluntary control.

Rectum

Last part of large intestine. Stores feces until a defecation Contains stretch receptors that activate when there is enough volume of feces in the rectum - this gives you the "urge" to void.

Duodenum

1st part of the small intestine. Accessory organs secrete substances into the duodenum to aid in chemical digestion of lipids, proteins, and carbohydrates.

Pyloric Sphincter

• Ring of muscle at the exit of the stomach.

• Regulates the release of chyme (stomach contents) from the stomach into the duodenum.

Gallbladder

Stores bile & contracts to release the bile.

Pharynx

• Passageway shared by both food and air.

• AKA - "throat"

Liver

• Largest internal organ.

• Produces bile which helps emulsify lipids into small droplets

• Stores fat-soluble vitamins (A, D, E, and K)

• Filters blood/detoxifyies waste.

Jejunum

2nd part of small intestine. Chemical digestion finishes & absorption of nutrients begins. Contains tiny finger-like projections called villi - increase the surface area of the intestinal lining to increase the rate of nutrient absorption.

Large Intestine/Colon

Larger in diameter than small intestine, but shorter in length. Functions: 1. Water reabsorption 2. Store food waste before defecation 3. Contains large amount of beneficial bacteria (gut flora) which make up the bulk of feces and also create vitamins B and K

Oral Cavity

Entrance for food. Begins mechanical & chemical digestion

Absorption

The process of absorbing nutrients into the bloodstream so they can be delivered to cells. Those nutrients are then used by the cell to maintain its structure and function.

Pancreas

Accessory organ with both endocrine and exocrine function.

• Endocrine - produces insulin & glucagon

• Exocrine - produces the following enzymes and secretes them into the duodenum:
• amylase - break down carbohydrates
• lipase - breaks down lipids (fats)
• trypsin - breaks down proteins

• Also produces and secretes bicarbonate into the duodenum. This is an alkaline substance that neutralizes the chyme exiting the stomach and entering the duodenum.

Digestion

The process of breaking down food, which is composed of macromolecules (carbohydrates, lipids, proteins, and nucleic acids), into individual monomers (monosaccharides, fatty acids & glycerol, amino acids, and nucleotides)

Tongue

Muscular organ that: 1. positions food 2. mixes food with saliva. 3. pushes bolus of food down pharynx during swallowing.

Soft Palate

• Fleshy area; back of roof of mouth

• During swallowing, lifts to block the nasal passages to prevent food/liquid from entering them.

Appendix

Projection inferior to the cecum. Although it is not a vital organ, it does house beneficial bacteria Prone to infection & inflammation - appendicitis

Cardiac Sphincter

• Ring of muscle @ top of stomach that regulates the entry of bolus into the stomach.

• Also prevents stomach contents from going back up the esophagus (regurgitation).

Elimination

The process of getting rid of waste that could not be digested or absorbed. In regards to the digestive system, the waste product is feces. The process of getting rid of feces is known as defecation.

Teeth

• Starts mechanical digestion
• increases the surface area for chemical digestion.