It More Than Just a Gut Feeling

The Digestive System

TAKS

Objective 2 – The student will demonstrate an understanding of living systems and the environment.

TEKS Science Concepts 3 The student uses critical thinking and scientific problem solving to make

informed decisions. The student is expected to: (B) evaluate promotional claims that relate to biological issues such as

product labeling and advertisements; 9 The student knows metabolic processes and energy transfers that occur in

living organisms. The student is expected to: (A) compare structures and functions of different types of biomolecules such

as carbohydrates, lipids, proteins, and nucleic acids; (C) investigate and identify the effects of enzymes on food molecules; and 10 The student knows that, at all level of nature, living systems are found

within other living systems, each with its own boundary and limits. The student is expected to:

(A) interpret the functions of systems in organisms including circulatory, digestive, nervous, endocrine, reproductive, integumentary, skeletal, respiratory, muscular, excretory, and immune;

(B) compare the interrelationships of organ systems to each other and to the body as a whole;

11 The student knows that organisms maintain homeostasis. The student is expected to:

(C) analyze the importance of nutrition, environmental conditions, and physical exercise on health

Engage

Watch this digestive system clip with gold medalist Bonnie Blair from PBS video Universe Within.

Explore Digestion Simulation As a result of participating in this simulation,

you will learn the structures and the functions of the digestive system.

Overall Digestive System Function Breaks up food physically and chemically. Stores food for a short period of time. Absorbs the digested foods and passes them

into the circulatory system. Stores and eliminates undigested food from

the body.

Explain

What are the two main types of digestion?

Physical/Mechanical: The physical breakdown of food by non-enzyme means.

Chemical: The use of enzymes to breakdown food.

List in Order the Pathways of Food Through the Digestive System.

The Mouth Pharynx Esophagus Stomach Small Intestine Large Intestine Rectum Anus

Oral Cavity

Oral Cavity (Mouth) What type of digestion occurs in the mouth? Both physical and chemical digestion takes place Tongue – taste

manipulates food prepares food for swallowing by

forming into a ball (bolus) Saliva is secreted

Moistens Protects mouth from abrasion Buffer against acids Kills some bacteria

What enzyme is secreted in saliva? Salivary Amylase

Enzyme that begins digestion of carbohydrates

Pharynx

Pharynx

Commonly call the throat Intersection of GLOTTIS and

opening of the esophagus (gullet) is found here

EPIGLOTTIS is a flap that closes the glottis when the act of swallowing occurs (Closes the Trachea)

Esophagus

Esophagus Does any digestion occur here? What is the word that describes the

movement that pushes the food down toward the stomach?

Connects PHARYNX and the STOMACH Peristalsis – wave-like contractions of

smooth muscles that push food down toward the stomach

Cardiac Sphincter – esophagus and stomach connect

Stomach

Stomach J Shaped organ that Stores and digests food. GASTRIC JUICES - pH of 1-2 Enzyme: pepsin which acts on proteins. HCl is needed to activate pepsin from its

inactive form pepsinogen. Gastrin – Horomone secreted to regulate

gastric juices. Mucus covers the inner lining to prevent the

acid from eating the tissue. The PYLORIC SPHINCTER or pylorus

connects the stomach to the small intestine and closes off the stomach at its posterior end.

Small Intestine

Small Intestine

Most breaking down of macromolecules occurs here.

6 meters in length Smaller diameter than the large intestine Divided into 3 sections:

Duodenum (first 25 cm) Jejunum Ileum

Digestion in Small Intestine Acid chyme enters duodenum Intestinal wall releases a hormone –

SECRETIN-signal pancreas to release a basic solution to neutralize the acid.

CHOLECYSTOKININ (CCK)- released to signal the gall bladder to release bile and the pancreas to release digestive enzymes

ENTEROGESTRONE-secreted to slow down peristalsis

Absorption and Distribution of Nutrients VILLI – small finger-like projections that

increase the surface area MICROVILLI – even smaller finger-like

projections on the VILLI LACTEAL – large lymph vessel found on

each villus (Absorbs FAT) Capillaries – small blood vessels found

on each villus (Absorbs all nutrients EXCEPT Fat)

Villi and Microvilli

Accessory Organs

Small Intestine Accessory Organs

Pancreas, Liver, and Gall Bladder

Add digestive enzymes, juices, and hormones to the small intestine

These chemicals help break down protein, fat and carbohydrates

Liver, Pancreas, and Gall Bladder

Liver produces bile which is needed to help digest fat.

Gall bladder stores the bile. Pancreas (Endocrine and Exocrine

function) produces enzymes need to finish digesting the main organic foods. It also produces insulin.

Pancreas and Gall Bladder

LIVER Regulates the contents of the blood. All blood contents enter the Liver via

the HEPATIC PORTAL VEIN.

Large Intestine Alone

Large Intestine (Colon) Main function of the COLON is to reabsorb

water from the small intestinal material. CECUM – T junction that connects the colon to

the small intestine APPENDIX – attached at the end of the cecum. Stores solid waste in the area called the

rectum. Bacteria (E. coli) live in this area of the body.

Produce odor, and Vitamin K

Large Intestine w/Small

Elaborate

Is Terry Better? You will relate two different types of cloth (Terry and Cotton) to the

increased surface area of the small intestine.

Goldfish Swallowing You will write a creative story describing what happens to a goldfish in

three distinct parts. Part 1: As it passes your lips to the cardiac sphincter. Part 2: As it passes through the cardiac sphincter until it reaches the place where the duodenum becomes the jejunum. Part 3: From the jejunum until it exits the body.