Chapter 5: Digestive System

A full set of practice flashcards covering human digestive system anatomy, stages of digestion, organs, accessory structures, glucose homeostasis, and metabolic thyroid regulation from ESP001 Biology Chapter 5.

What is the human digestive system and what is its primary responsibility?

The digestive system is a human body system responsible for breaking down food into nutrients, which pass into the circulatory system so cells can utilize them for energy, growth, or cell repair.

What are the two main divisions of the human digestive system?

1. Digestive tract (gastrointestinal tract): a long tube through which food passes. 2. Accessory organs: organs essential for digestion through which food does not pass.

What are the four primary functions of the digestive system?

1. Ingesting food. 2. Breaking down food into nutrient molecules. 3. Absorbing molecules into the bloodstream. 4. Removal of indigestible remains.

What are the four stages of food processing in order?

1. Ingestion (taking in food). 2. Digestion (breaking down large food particles into nutrient molecules). 3. Absorption (nutrient molecules taken up by body cells). 4. Excretion (removing undigested food and leftover waste from the body).

Which organs constitute the upper digestive tract?

The oral cavity, pharynx, epiglottis, esophagus, and stomach.

Which organs constitute the lower digestive tract?

The small intestine, large intestine, and anus.

Which structures are classified as accessory organs of the digestive system?

The pancreas, salivary glands, liver, gallbladder, teeth, and tongue.

Where are the salivary glands located and what liquids do they produce?

They are located between the ear and mouth, under the tongue, and they produce and secrete saliva.

What are the four main components of saliva and their functions?

1. Water: liquifies and dissolves food. 2. Mucus: makes food slippery and easy to move down the tract. 3. Amylase: enzyme that starts breaking down starch in the mouth. 4. Lysozyme: enzyme that eliminates harmful bacteria.

Which five basic flavors are detected by taste buds on the tongue?

Sweet, sour, salty, bitter, and umami.

Which five basic taste regions on the human tongue are mapped in this diagram?

Bitter, sour, umami, sweet, and salty.

How many teeth do human adults have, and what is their primary role?

Adults have a total of $32$ teeth, which chew and break down larger food particles into smaller ones for easier swallowing.

Based on this diagram, what are the four distinct types of human teeth shown from left to right?

Incisor, Canine, Premolar, and Molar.

What are the quantities and functions of incisors, canines, premolars, and molars in adults?

1. Incisors: $8$ flat front teeth used for biting and cutting food. 2. Canines: $4$ sharp teeth beside incisors used for tearing food. 3. Premolars: $8$ teeth beside canines used for chewing and grinding food. 4. Molars: $12$ back teeth used for grinding food.

What three structural layers make up a tooth?

1. Enamel: outer hard, protective white coating. 2. Dentin: middle layer under enamel made of calcium salts and proteins. 3. Pulp: inner part containing living cells, nerves, and blood vessels.

What three main structural layers of a tooth are shown in this anatomical cross-section?

Enamel, Dentin, and Pulp Cavity.

What is the function of the epiglottis during swallowing?

The epiglottis is a flap of tissue that covers the larynx (voice box) during swallowing so food enters the esophagus instead of the trachea.

What wave-like muscular contraction process depicted here propels food down the esophagus?

Peristalsis.

What is the role of the gastroesophageal sphincter during food propulsion into the stomach?

It is a smooth muscle at the entrance of the stomach that relaxes to allow food to enter and then closes to prevent food from moving back up.

What three substances are secreted by the walls of the stomach, and what are their roles?

1. Hydrochloric acid (HCl): a strong acid secreted by tiny glands that liquifies food. 2. Alkaline mucus: covers stomach walls to protect them from strong acid. 3. Pepsin: enzyme that initiates the breakdown of proteins in food.

What muscle valve regulates the release of food from the stomach into the small intestine?

The pyloric sphincter (valve), which relaxes to release food in small amounts.

What is the length of the small intestine and what is its role in food digestion?

The small intestine is $6$ feet long and performs the majority of the food breakdown (digestion) using enzymes secreted by its walls, receiving acidic food, pancreatic juices, and bile.

How are absorbed nutrient molecules processed after leaving the small intestine?

Nutrient molecules enter blood vessels leading to the liver, where they are stored, converted into other essential molecules, or transferred into circulation. The liver also removes toxins.

What are the dimensions and primary functions of the large intestine?

The large intestine is $4.9$ feet long and wide. Its functions are absorbing remaining water, sodium, and potassium into the bloodstream, and producing feces.

How do the internal and external anal sphincters differ in their control of defecation?

The internal anal sphincter is controlled involuntarily by the spinal cord and relaxes when feces press against it. The external anal sphincter is controlled voluntarily by us to allow defecation when relaxed.

What is the liver's role in bile production and emulsification?

The liver produces bile, a green liquid that breaks down large fat globule particles into small droplets in the small intestine (emulsification), aiding digestive enzymes.

What process of fat breakdown into smaller droplets by bile salts is illustrated here?

Emulsification of a fat globule by bile salts into emulsified fat droplets.

Where is bile stored, how does it reach the small intestine, and what causes gallstones?

Bile is stored in the gallbladder and sent to the small intestine via the bile duct. Gallstones are large salt crystals formed from excessive cholesterol consumption that block the bile duct or gallbladder.

What four substances are secreted in pancreatic juices into the small intestine?

1. Lipase: breaks down lipids (fats). 2. Amylase: breaks down starch. 3. Protease: breaks down proteins. 4. Sodium bicarbonate: neutralizes stomach acid so enzymes can function.

Which two pancreatic hormones maintain blood glucose homeostasis?

Insulin and glucagon.

According to this diagram, what distinguishes Type 1 diabetes from Type 2 diabetes?

In Type 1 diabetes, the pancreas fails to produce insulin. In Type 2 diabetes, the body produces insulin but cells fail to respond to it properly at the insulin receptor.

What are the clinical differences between Type 1 and Type 2 diabetes mellitus?

Type 1 ('juvenile diabetes') begins in adolescence ($11$\text{--}$13$ years) due to pancreas failure to make insulin, requiring glucose monitoring and insulin injections. Type 2 begins in late adulthood ($50$\text{--}$70$ years), linked to overweight or family history, where cells fail to respond to insulin, managed via medication and diet.

How is cellular metabolism regulated by the endocrine system?

Cellular metabolism is regulated by thyroid hormone secreted by the thyroid gland, which is controlled by Thyroid Stimulating Hormone (TSH) released from the pituitary gland via negative feedback.

What is hypothyroidism, what causes it, and what are its symptoms in children versus adults?

Hypothyroidism is underproduction of thyroid hormone (often caused by low iodine in diet). In children, it causes cretinism (weak skeleton and nervous system). In adults, it causes tiredness, cold intolerance, and weight gain.

What is hyperthyroidism, what causes it, and what are its symptoms?

Hyperthyroidism is overproduction of thyroid hormone causing a high metabolic rate (often caused by thyroid or pituitary tumors). Symptoms include high blood pressure, weight loss, restlessness, and irregular heart rate.

What thyroid enlargement condition is illustrated in this diagram?

Goiter.

What causes a goiter to form?

A goiter is an enlargement of the thyroid gland caused by excessive TSH or iodine deficiency.