Human Anatomy Unit 2

Mouth (Function)

The entrance of the digestive system responsible for taking in food and initiating both mechanical and chemical digestion

Mouth (Anatomy)

The roof of the oral cavity seperates the nasal cavity from the mouth and consists of two parts: an anterior hard palate (supported by bone) and a posterior soft palate (made of muscle)

Mechanical Digestion

• Teeth and tongue

• Teeth chew (masticate) food into smaller pieces, while the tongue mixes food and forms it into a swallowable mass called a bolus. This physically increases the surface area of the food for enzymes to work on

Chemical Digestion

Saliva moistens and lubricates the food for easier swallowing. Saliva also contains the enzyme salivary amylase, which begins breaking down complex carbohydrates (starches) into simpler sugars

Uvula

A muscular projection hanging down from the soft palate at the back of the mouth.

Purpose of the Uvula

To secrete thin saliva that moistens the mouth and throat

Salivary Glands

Secrete saliva which contains digestive enzymes (salivary amylase) for carbohydrates

Salivary Amylase

An enzyme in saliva that begins the chemical digestion of starch, as well as a buffer called bicarbonate and antimicrobial compound called lysozyme

Pharynx

A passageway behind the mouth and nasal cavity that serves as a shared opening for food and air. During swallowing, a flap of cartilage called the epiglottis covers the airway to direct food into the esophagus and prevent choking.

Esophagus

Passageway where peristalsis pushes food to stomach

Peristalsis

The involuntary contraction of the esophagus to propel food down to your stomach

Small Intestine (Function)

The primary site of chemical digestion and nutrient absorption

Small Intestine (Anatomy)

It is a long, coiled organ averaging about 18 feet in length. Its mucosa contains fingerlike projections called villi, which give the wall a soft, velvety appearance.

What covers each villus, and what forms the "brush border"?

Each villus is covered by columnar epithelial cells containing thousands of microscopic extensions called microvilli. Together, the microvilli form a fuzzy brush border.

Small Intestine (Nutrient Absorption)

The villi and microvilli greatly increase the surface area of the small intestine, allowing for more efficient absorption of digested nutrients

Small Intestine (Lactase)

The digestive enzyme that breaks down lactose into glucose and galactose

Small Intestine (Maltase)

The digestive enzyme that breaks down maltose into glucose molecules

Small Intestine (Sucrase)

The digestive enzyme that breaks down sucrose into glucose and fructose

Large Intestine (Primary Function)

To absorb water and salt, which helps prevent dehydration and maintain overall body homeostasis. Also to form feces.

Large Intestine (Function)

Bacteria breaks down indigestible material and produce essential B-complex vitamins and most of the body's needed vitamin K.

Large Intestine (Anatomy)

About 4.5 ft in length

Stomach (Function)

1. Stores food.

2. Begins the digestion of proteins.

3. Regulates the movement of food into the small intestine.

How does the stomach perform mechanical digestion?

It temporarily stores food and churns it, mixing the food with gastric juices to help break it down.

Chyme

A thick, soupy liquid consisting of partially digested food mixed with gastric juice.

What does the stomach produce?

Gastric Juice

What are the three key components of gastric juice and their functions?

1. Pepsin: An enzyme that begins protein digestion

2. Hydrochloric Acid (HCl): Creates the acidic environment needed for pepsin to function

3. Mucus: Protects the stomach lining from acid and digestive enzymes

Stomach (Movement into Small Intestine)

The stomach controls the release of chyme so that small amounts enter at intervals rather than all at once

How long does it normally take for the stomach to empty its contents?

Within about 2 to 6 hours.

Liver (Function)

An accessory organ that:

1. Processes blood from the GI tract

2. Detoxifies harmful substances

3. Produces bile

Liver (Anatomy)

It lies in the upper right section of the abdominal cavity, directly beneath the diaphragm. It contains approximately 100,000 lobules, which act as its structural and functional units.

Liver (Blood Supply)

The hepatic portal vein carries blood from the capillary beds of the GI tract. The blood then passes through the capillaries of the liver lobules, where it is filtered and processed.

Liver (Detoxification)

It removes poisonous substances from the blood and neutralizes/detoxifies them, shielding the body from harmful chemicals and waste products.

Gallbladder (Function)

Stores and releases bile to help digest fats

Gallbladder (Anatomy)

A pear-shaped organ located beneath the liver

What does the gallbladder do to bile prior to digestion?

It stores and concentrates bile produced by the liver

How and where is bile released during digestion?

When needed, bile is released through the bile ducts into the duodenum (the first section of the small intestine). Bile helps break large fat droplets into smaller droplets (emulsification), making fats easier for lipase to digest.

Gallstones

Form when substances in bile harden into stone-like pieces inside the gallbladder. They can sometimes block the bile ducts and cause pain or other digestive problems

Pancreas (Digestive Function)

Produces pancreatic juice, which contains enzymes that digest the macromolecules

Pancreas (Anatomy)

A gland located behind the stomach

Pancreas (Chemical Digestion of Fats)

Pancreatic lipase hydrolyzes fats into monoglycerides and fatty acids

Pancreas (Chemical Digestion of Carbohydrates)

Pancreatic amylase begins carbohydrate digestion, and intestinal enzymes (including brush border enzymes) complete the breakdown into simpler sugars

Pancreas (Chemical Digestion of Proteins)

Trypsin begins protein digestion, and intestinal enzymes finish breaking proteins down into amino acids

PANLAT

Digestive Enzymes

• PAN = Pancreas

• L=Lipase (lipids)

• A=Amylase (starch)

• T=Trypsin (Protein)

Pancreas (Sodium Bicarbonate)

It neutralizes the acidic chyme entering the small intestine from the stomach, creating a more suitable pH environment for digestive enzymes to function

Appendix (Function)

1. Aids in fighting infections

2. Contributes to maintaining the population of beneficial bacteria in the large intestine

Rectum (Structure and Function)

It is the final straight portion of the large intestine that acts as a temporary storage area for feces until defecation.

How does the rectum signal the brain when it is ready to evacuate waste?

Stretch receptors in its walls detect fullness and send signals to the brain.

Anus

It is the terminal opening of the digestive tract that controls the release of waste. It uses two sphincters:

• Internal sphincter: Involuntary control

• External sphincter: Voluntary control

What is gluten, and how is it processed in a healthy digestive system?

Gluten is a protein found in wheat, rye, and barley. It is broken down into amino acids and absorbed into the circulatory system like any other protein.

What happens to the small intestine in a person with celiac disease?

The immune system misidentifies gluten as a foreign pathogen. This triggers an autoimmune response that inflames the small intestine and damages the villi and microvilli.

How does gluten sensitivity differ from celiac disease?

Gluten sensitivity causes similar symptoms, but it does not cause physical damage to the intestinal wall.

What is the primary purpose of teeth in digestion?

They mechanically break food into smaller pieces, increasing its surface area so digestive enzymes can work more effectively.

How many primary (baby) teeth and adult teeth do humans develop?

• Baby teeth: 20 smaller teeth appearing in the first two years.

• Adult teeth: 32 teeth (including wisdom teeth/third molars).

What are the two main anatomical divisions of a tooth?

• Crown: The portion above the gum line.

• Root: The portion below the gum line.

How does the liver regulate blood glucose levels during high and low blood sugar states?

High glucose (with insulin): Stores glucose as glycogen.

Low glucose: Breaks down stored glycogen to release glucose (or converts glycerol and amino acids into glucose).

How does the liver help regulate blood cholesterol levels?

It converts a portion of blood cholesterol into bile.

How does the pancreas respond when blood glucose levels rise rapidly?

It secretes a surge of insulin into the bloodstream to lower glucose levels back to homeostasis.

What occurs in Type 1 diabetes regarding insulin production?

The pancreas does not manufacture sufficient amounts of insulin.

What are the 5 major processes of digestion?

1. Ingestion: Taking food in through the mouth.

2. Digestion: Mechanical or chemical breakdown of food into smaller pieces/molecules.

3. Movement: Transporting contents along the GI tract (e.g., via peristalsis).

4. Absorption: Nutrients cross the GI tract lining into cells and blood vessels.

5. Elimination: Discharging indigestible waste through the anus (defecation).

What causes GERD, and why does it produce a burning sensation?

GERD is chronic acid reflux. It occurs because the contents of the stomach are more acidic than those of the esophagus. The acidic stomach contents pass upward into the esophagus, eroding its thin lining and creating heartburn.

How do over-the-counter antacids relieve acid reflux?

They have a basic pH, which neutralizes stomach acid.

Trace the four main regions of the colon in order.

1. Ascending colon: Travels up the right side of the body.

2. Transverse colon: Crosses the abdomen below the liver and stomach.

3. Descending colon: Travels down the left side of the body.

4. Sigmoid colon: Connects to the rectum.

Why is water monitored for coliform bacteria?

A high count indicates that a significant amount of feces has entered the water. The more feces present, the greater the possibility that disease-causing bacteria are also present.

What is the composition of normal feces?

Approximately 3/4 water and 1/4 solid wastes (bacteria, dietary fiber, and indigestible material).

What triggers the urge to defecate?

Peristalsis forces feces into the rectum, stretching the rectal wall. This triggers nerve impulses to the spinal cord, causing rectal contraction and sphincter relaxation.

Disorders of the colon

1. Diarrhea

2. Constipation

3. Diverticulosis

4. Irritable Bowel Syndrome (IBS)

5. Inflammatory Bowel Disease (IBD)

6. Polyps and Cancer

What causes diarrhea, and what is its physiological purpose?

Infection or nervous stimulation irritates the intestinal wall, increasing peristalsis and preventing water absorption. This rapidly rids the body of infectious organisms. Characterized by bowel movements that are loose or watery

What are the common causes of constipation?

Diets lacking whole grains/fiber and regularly ignoring the urge to defecate. When a person is constipated, the feces are dry and hard, making it difficult for them to be expelled.

What is diverticulosis?

The formation of small mucosal pouches where food can collect, created when the mucosa pushes through weak spots in the muscle layer (commonly in the descending colon).

What is Irritable Bowel Syndrome (IBS)?

A condition where the muscle layer contracts forcefully without normal coordination, causing cramps, gas, constipation, and explosive stools.

What is Inflammatory Bowel Disease (IBD), and what are its two most common forms?

IBD is a collective term for chronic inflammatory disorders of the digestive tract. Its two main types are Ulcerative Colitis and Crohn's Disease.

Compare Ulcerative Colitis and Crohn's Disease

• Ulcerative colitis (IBD): Limited to the large intestine and rectum; causes bleeding, diarrhea, and cramps.

• Crohn's disease (IBD): Usually isolated to the small intestine, but can affect any part of the GI tract.

Polyps and Cancer

The colon is subject to the development of polyps, small growths arising from the epithelial lining. Polyps, whether benign or cancerous, can be removed surgically.

How does dietary fat increase the risk of colon cancer, and how does fiber help?

Dietary fat increases bile secretion (bacteria may convert bile salts to carcinogens). Fiber helps inhibit colon cancer development.

What is hepatitis?

Hepatitis is inflammation of the liver.

Compare the transmission methods and vaccine availability for Hepatitis A, B, and C.

• Hepatitis A: Sewage-contaminated food/water. (Vaccine available)

• Hepatitis B: Sexual contact, blood transfusions, needles. (Vaccine available)

• Hepatitis C: Contact with infected blood; leads to chronic hepatitis, liver cancer, and death. (No current vaccine)

What is cirrhosis, and how can it be managed?

A chronic liver disease where healthy tissue becomes fatty and is replaced by inactive fibrous scar tissue. Cirrhosis of the liver is often seen in alcoholics due to malnutrition and the excessive amounts of alcohol the liver is forced to break down. The liver can recover if regeneration exceeds damage, but severe failure requires a liver transplant.

What are the functions of Gastrin, Secretin, and CCK?

Digestive hormones involved in the regulation of digestion

• Gastrin: Stimulates gastric juice production in the stomach.

• Secretin: Stimulates the pancreas to release neutralizing pancreatic juice.

• CCK: Stimulates pancreatic juice secretion, increases liver bile production, and contracts the gallbladder.

Explain whether or not starch and glucose will pass through the cell membrane.

The membrane is selectively permeable, meaning small molecules like glucose can pass through, but larger molecules like starch cannot. Glucose diffuses through the membrane, while starch stays inside because its molecules are too large to fit through the membrane’s pores.

Accessory Organs

Salivary glands, liver, gallbladder, pancreas