Biology Chapter 25: Nutrition and Digestion

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Questions and Answers

What are the primary functions of the pancreas?

Releasing hormones and aiding in fat digestion

Producing bile and storing it in the gallbladder

Acting as both an exocrine and endocrine gland (correct)

Metabolizing alcohol and removing toxins

What stimulates the gallbladder to release bile?

The arrival of fat content in the duodenum (correct)

The presence of carbohydrates in the intestines

High levels of glucose in the bloodstream

Direct nerve impulses from the pancreas

Which substances does the liver metabolize?

Only nutrients absorbed from food

Hormones produced by the pancreas

Alcohol, drugs, and other toxins (correct)

Bile salts and bile pigments

What components make up bile?

Bile salts and bile pigments Signup and view all the answers

What is the relationship between veins from the stomach and intestine and the liver?

Veins carry blood from the stomach and intestine to the liver Signup and view all the answers

What is the primary source of carbohydrates in an optimal diet?

Grains, fruits, and vegetables Signup and view all the answers

Which macronutrient contains the highest amount of calories per gram?

Fats Signup and view all the answers

What percentage of total caloric intake from fats is associated with being significantly overweight?

More than 35% Signup and view all the answers

What is the function of essential amino acids in the diet?

They must be obtained through food since the body cannot manufacture them. Signup and view all the answers

How is the Body Mass Index (BMI) calculated?

Weight in kg divided by height in meters squared Signup and view all the answers

Why have many animals lost their ability to manufacture certain substances?

Due to evolutionary changes over time Signup and view all the answers

Which of the following is an example of a food that provides protein?

Dairy products Signup and view all the answers

What does an optimal diet mainly consist of?

More carbohydrates than fats and a significant amount of protein Signup and view all the answers

What is the primary function of hydrochloric acid (HCl) in the stomach?

To activate pepsinogen into pepsin Signup and view all the answers

Which cells in the stomach are responsible for secreting pepsinogen?

Chief cells Signup and view all the answers

What is the primary role of bile salts in fat digestion?

To emulsify fats Signup and view all the answers

What does the term 'chyme' refer to in the digestive system?

Partially digested food mixed with gastric juice Signup and view all the answers

What structures in the small intestine increase the surface area for absorption?

Villi and microvilli Signup and view all the answers

Which part of the small intestine is primarily responsible for the absorption of water and digested products?

Ileum Signup and view all the answers

What is the typical pH of gastric juice in the stomach?

2 Signup and view all the answers

What is the main function of the large intestine?

Compaction and storage of undigested material Signup and view all the answers

What primarily protects the epithelial cells of the stomach from gastric acid?

Alkaline mucus Signup and view all the answers

Which enzymes are secreted by the pancreas to aid in protein digestion?

Trypsin and chymotrypsin Signup and view all the answers

Which bacterium is associated with an increased susceptibility to gastric ulcers?

Helicobacter pylori Signup and view all the answers

What structure does the pancreas use to empty its secretions into the duodenum?

Pancreatic duct Signup and view all the answers

In what organ are the majority of digestive enzymes produced?

Pancreas Signup and view all the answers

What percentage of fluid absorption occurs in the large intestine?

6% to 7% Signup and view all the answers

What is the role of the small intestine in digestion?

To breakdown carbohydrates, proteins, and lipids Signup and view all the answers

Which of the following statements about the small intestine is true?

Its lining increases surface area for absorption. Signup and view all the answers

How many primary teeth do children have before they are replaced by adult teeth?

20 Signup and view all the answers

What is the role of salivary amylase in the digestive process?

Initiates the breakdown of starch into maltose Signup and view all the answers

Which structure prevents food from entering the respiratory tract during swallowing?

Epiglottis Signup and view all the answers

What type of muscle surrounds the upper third of the esophagus, allowing voluntary control of swallowing?

Skeletal muscle Signup and view all the answers

What is peristalsis?

Rhythmic waves of contractions propelling food Signup and view all the answers

What controls the movement of food from the esophagus into the stomach?

A ring of circular smooth muscle called a sphincter Signup and view all the answers

What can occur when the sphincter muscle relaxes excessively, allowing stomach acid to move into the esophagus?

Acid reflux Signup and view all the answers

What effect does stomach contents being brought back out during vomiting have on the sphincter muscle?

It can lead to dysfunction and acid reflux Signup and view all the answers

What is the main function of the mucosa layer in the gastrointestinal tract?

Facilitates nutrient absorption Signup and view all the answers

What distinguishes heterodont dentition from homodont dentition?

Heterodonts have teeth of different types, while homodonts have the same type of teeth. Signup and view all the answers

Which type of dentition modification is typical for carnivorous mammals?

Prominent canines and blade-like premolars Signup and view all the answers

Which layer of the gastrointestinal tract is primarily made up of connective tissue?

Submucosa Signup and view all the answers

What is an example of a specialized trait found in herbivorous mammals?

Large, flat molars with ridges Signup and view all the answers

What characteristic of human teeth reflects their omnivorous diet?

Carnivorous teeth in the front and herbivorous teeth at the back Signup and view all the answers

Which of the following statements about the muscularis layer is true?

It has two layers of muscle tissue. Signup and view all the answers

How do birds that lack teeth process their food?

Breaking food down in the gizzard Signup and view all the answers

Study Notes

Chapter 25: The Path of Food Through the Animal Body

Food provides energy and essential molecules.
Optimal diets have more carbohydrates than fat, and a significant amount of protein.

Nutritional Plate

The ChooseMyPlate.gov diagram illustrates the food groups.
The model shows the relative proportions of fruits, vegetables, grains, protein and dairy products.

Food for Energy and Growth

Carbohydrates (obtained from grains, fruits, vegetables) contain approximately 4.1 calories per gram.
Dietary fats (found in oils, margarines, butters, fried foods, meats, processed snacks) contain approximately 9.3 calories per gram.
Proteins (dairy, poultry, meat, grains) contain approximately 4.1 calories per gram.
Overweight is common in wealthy countries, due to overeating and high-fat diets (over 35% of total calories).
Body Mass Index (BMI) is a measure of appropriate body weight (weight (kg) / height (meters squared).

Digestive Systems

Heterotrophs are categorized by their food sources: herbivores (plants), carnivores (meat), and omnivores (plants and animals).
Sponges digest food intracellularly, while other animals digest extracellularly within a digestive cavity.
Cniderians and flatworms have a gastrovascular cavity (a single opening serving as both mouth and anus).
The digestive tract (alimentary canal) in other animals has a separate mouth and anus, allowing for specialization and one-way movement (physical force: chewing etc.)
Chemical digestion in the intestine involves hydrolysis reactions.
Products are absorbed into the blood, undigested are passed out through the anus.

Human Digestive System

The gastrointestinal tract comprises layers: mucosa (innermost epithelium), submucosa (connective tissue), muscularis (two muscle layers), and serosa (outer connective tissue).

The Mouth and Teeth

Vertebrates have digestive system specializations that reflect their lifestyles.
Many have teeth (mastication) to break food into small pieces and mix with fluid secretions.
Birds use their gizzard to process food.
Reptiles and fish have homodont dentition (all teeth are the same).
Mammals have heterodont dentition (diverse types of teeth): incisors (nipping), canines (tearing), premolars and molars (grinding).
The modifications of dentition reflect the various diets of different mammals.

Human omnivorous diet

Humans have specialized teeth for both plant and animal material (carnivorous in front, herbivorous in the back).
Children have 20 teeth, replaced by 32 adult teeth.
Tooth structure includes enamel, dentin, pulp, gingiva, bone, cementum, and root canals.
Tongue mixes food with saliva to aid in the swallowing process.
Saliva contains amylase, which initiates the breakdown of starch to maltose (a disaccharide).
Food moves into the esophagus during swallowing, prevented from going into the respiratory system by epiglottis.

The Esophagus and Stomach

The esophagus (muscular tube) connects the pharynx to the stomach.
The upper third employs skeletal muscle for voluntary swallowing, the lower two-thirds use involuntary smooth muscle; peristalsis propels food to the stomach.
Sphincters (circular smooth muscle rings) control the movement of food between the esophagus and stomach.
Sphincter contractions prevent food from returning to the esophagus.
Vomiting can cause stomach contents to return to the esophagus.
Stomach acid reflux occurs when stomach acid moves into the esophagus, producing heartburn.
Gastric juice secreted by the gastric glands contains HCL secreted by parietal cells.
Pepsinogen, secreted by chief cells, is activated by HCL into pepsin, a protein-digesting enzyme.
Chyme is the mixture of partially digested food and gastric juice.

The Small and Large Intestines

Intestine is the main digestive organ.
Chyme is introduced to the small intestine in small portions.
The small intestine (jejunum) continues digestion and absorbs water and digested nutrients.
The small intestine lining is folded into ridges (villi), covered with microvilli (tiny projections).
The pancreas (a near-stomach gland) secretes fluid into the duodenum (the first part of the small intestine), containing various enzymes (trypsin, chymotrypsin, pancreatic amylase, lipase, bicarbonate) aiding digestion.
The pancreas is endocrine as well, producing hormones in the islets of Langerhans (insulin and glucagon.
Bile, produced by the liver and stored in the gallbladder, emulsifies fats and aids in their digestion by the enzyme lipase.
The arrival of fatty foods triggers gallbladder contraction to release bile.
The large intestine (shorter & wider than small) compacts and stores undigested material as feces.
Water and essential substances (sodium, vitamin K) are reabsorbed in the large intestine.

Accessory Digestive Organs

Veins from the stomach and intestines carry blood to the liver
The liver metabolizes alcohol and drugs.
The liver removes toxins (pesticides, carcinogens) and converts them to less toxic forms.

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Description

Explore the critical concepts of nutrition and the path of food through the animal body in this chapter. Understand the roles of carbohydrates, fats, and proteins, and learn how a balanced diet contributes to health. The quiz also delves into digestive systems and the importance of body mass index (BMI).