The Digestive and Excretory SystemsBy. Emir Fils-Aimé, Alexis Murray,

and Melody Schwenk

AP Biology-Ms. Stein, Due 4/14/10

The Digestive System: Part I

“Food’s Highway”

Digestion• To be processed and expelled, food

must pass through various digestive organs

• Food goes through the following organs: Mouth Esophagus Stomach Small and Large Intestines Rectum Anus

The Oral Cavity, Pharynx, Esophagus

• Food begins digestion in the mouth

• Both physical and chemical digestion of food begin in the oral cavity

• The food is broken down physically by chewing, making it easier to swallow and increase surface area.

• The presence of food in the mouth activates salivary glands.

• The saliva starts the breaking down of food.

-An enzyme, salivary amylase, hydrolyzes starch and glycogen.

• The tongue manipulates food into a ball called the bolus. It is pushed into the back of the throat to the pharynx

• To prevent choking, when we swallow the epiglottis blocks the windpipe.

• From the pharynx the food is conducted to the stomach by the esophagus.

• Swallowing begins voluntarily but is taken over involuntarily by peristalsis.

• Peristalsis is the contraction of smooth muscle to help move food along the digestive tract.

The Stomach • The stomach stores food

and performs the preliminary steps of digestion.

• Before storing food, the stomach secretes gastric juice. This juice mixes with the food.

• Gastric acid binds cells together in meat and plant material. It also kills most bacteria in food.

• Pepsinogen, an inactive form of pepsin is also secreted so the gastric juice doesn’t burn the stomachs lining.

• Every 20 seconds the stomachs contents are mixed by the churning of smooth muscles.

• As a result of mixing and enzyme action, the food in the stomach becomes a nutrient rich broth called acid chyme.

• The stomachs ends are usually both closed off. At the top, its closed by the cardiac orifice, which only opens when a bolus arrives. – Backflow may occur, causing heartburn

• At the bottom, the stomach is closed off by the pyloric sphincter. – It helps regulate the passage of chyme into the

intestine, one squirt at a time.

The Small Intestine • Most of enzyme

hydrolysis occurs in the small intestine.

• Acid chyme from the stomach mixes with digestive juices from the pancreas, liver, gallbladder, and gland cells of the intestinal wall in the duodenum.

• The duodenum is the first 25 cm of the small intestine.

• The jejunum and ileum function mainly to absorb nutrients and water.

• The small intestine contains villi which also contain microvilli. These structures help to increase the rate of nutrient absorption.

• Small vessels of the lymphatic system called lacteal.

• Capillaries within the villi converge into the hepatic portal vein, which leads to the liver. – It ensures that the liver is the first to receive

access to sugars and amino acids

The Large Intestine• The large intestine is also known as the colon. • The appendix is located on the large intestine. It

is dispensable. • The large intestines major function is to recover

water that has entered the alimentary canal. • The wastes of the digestive tract, the feces,

become more solid as they move along the colon by peristalsis.

• The terminal portion of the colon is called the rectum. Feces are stored here until they can be eliminated.

Key Terms • Mouth- the first part of digestion takes place here. Chemical and

mechanical digestion start here.

• Esophagus- tube between mouth and stomach. Forces food down to stomach by peristalsis

• Stomach- sac like muscular organ attached to esophagus. Stores food and starts digestion.

• Small Intestine- long tube winding from the stomach. Named small intestine for its diameter not length

• Large Intestine- tube that food travels through after the small intestine. Also called the colon.

• Gall-bladder-small sac like organ by the duodenum. Stores and releases bile.

• Duodenum- the first 25 cm of the small intestine.

• Liver- organ above the stomach. It filters toxins and makes bile and blood proteins.

The Excretory System: Part II

Urine Production• The process of producing the fluid waste

“urine” occurs in four steps:– Filtration: Filtrate from the blood is

collected by the excretory tubule. Water and solutes (which make up the filtrate) are forced across the selectively permeable membranes of capillary clusters and then into the excretory tubule.

– Reabsorption: The transport epithelium reabsorbs valuable solutes from the filtrate and returns them to the body fluids.

–Secretion: The remaining substances, such as toxins and excess ions are removed and added to the excretory tubule.–Excretion: The filtrate leaves the

system and the body.

The Kidneys• They are the principal site for water

balance and salt regulation; they are found in a pair

• Receive blood from the renal artery and it is drained from the renal vein; blood flow through the kidneys is voluminous

• Urine exits them through the ureters and they drain into a single urinary bladder and from there, the urine exits through the urethra (found near the vagina in females and in the penis in males)

• Consist of two different regions: the renal cortex (outer part) and the renal medulla (the inner part)

• Contains about a million nephrons; each nephron has a single long tubule and a ball of capillaries called a glomerulus

• The blind end of the excretory tubule forms a cup shaped swelling known as a “Bowman’s capsule”-it surrounds the glomerulus

• The initial filtration of blood, which is nonselective, occurs in the Bowman’s capsule first

• The filtrate then travels in spiraled direction to other regions including the proximal tubule, the loop of Henle, and the distal tubule which empties into the collecting duct

• From the collecting duct, processed filtrate is transported to the renal pelvis and drained by the ureters

• ADH (Antidiuretic hormone) helps to regulate reabsorption levels and adjust the volume and osmolarity of urine, by increasing and decreasing permeability in the epithelium

• A special tissue known as the juxtaglomerular apparatus (JGA) affects blood volume and pressure levels in the glomerulus

Activities: Part III

The Excretory System Crossword Puzzle

E N E K D G Z Q R S K N U B N R K U C C V L E L L N R X U I G R N L S F X Z G C F N U P M Z Y L I H E K I A K R A I I H P D Q S H O U Q Z T O T I D J J S E L A

R B R X P R L R E N Q S E D V K Y A R K D O A G E A O R L H Z Y L E Y L A S F U E I Q M I N C N O D G L N R U S A B K S R I O J V R U S V F Q T E S M D M Z N X Y L R Q E L N E N I W U H C V X C X I T G W A A T S B K Q A J O F Z U L B P V Y D T J Q A D H Y E R M V O V H R J A L A C U R B D L O H A K F W P K I D N E Y S R Y Q O W A Y Q Y X V K O K M P T Z I K L L L B Z W K M W V U Z O B Y I N I H G Z K X C W Y F S O L F O L U O N A M N X D P A Y J T D D W R N T T Z D S U H V Y E T S A W S U O N E G O R T I N L Q K O Q Y Y Z P V G I D V Q R E V I L F S Q X

Q O O T I C Q C Z K K Z A I L N T O W E H X E G D D I T Z Q A J L T J O L B P K

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BLADDER BOWMANS CAPSULE

GLOMERULUS KIDNEYS

LIVER LOOP OF HENLE

NEPHRON NITROGENOUS WASTE

UREA URETER

Fill in the Blank1.After chewing, food goes down your throat or __________ .

2.Wave like muscle contractions called __________ move food through the digestive tract from one processing station to the next.

3.The three sections, duodenum, jejunum, and ileum, in the __________ perform similar but different functions. However, ultimately nutrients are absorbed

through the lining.

4.The __________ is located between the esophagus and small intestine; it’s primary function is to process and break down food into small enough parts so

that it is passed through the rest of the digestive tract.

5.Salivary glands, pancreas, liver, and the gallbladder are all __________ of the digestive system.

6.Partially digested food, called _________ , when combined with bile may be excreted from the body as a bowel movement.

7.The __________ is the last part of the large intestine that ultimately releases fecal matter from the body.

8.Waste products from the food you eat are stored in the __________ to be collected and processed into feces.

9.Food and drinks are transported down the __________ into the stomach.

10. Not only do __________ offer protection for the small intestine, but they also expand the space to allow molecules to enter easily.

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PharynxEsophagusStomach

PeristalsisChyme

Small IntestineLarge Intestine

VilliRectum

Accessory GlandsAnus

Label the Diagram

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The End!

Informative Resources• http://digestive.niddk.nih.gov/ddiseases/pubs

/yrdd/• http://science.nationalgeographic.com/scienc

e/health-and-human-body/human-body/digestive-system-article.html

• http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookEXCRET.html

• http://biology.clc.uc.edu/courses/bio105/kidney.htm