CHAPTER 38:THE DIGESTIVE AND EXCRETORY SYSTEMS

CONCEPTS- Organs- Functions

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ORGANS: THE MOUTH

Breakdown of food begins in the mouth.

Starches are broken down by an enzyme called salivary amylase.

Teeth are NOT bones!Teeth are anchored by jaw bones

mastication, beginning of mechanical digestionSaliva: moistens food (easier to

chew/swallow)Chemical digestion: enzymes

COMPONENTS OF THE DIGESTIVE SYSTEM

CONTINUED…

Stomach: continues the mechanical and chemical digestion of foodChemical digestion: stomach

produces HCl, which activates enzymes that digest proteins

Mechanical digestion: stomach muscles contract to churn and mix stomach fluids and food, gradually producing chyme. Chyme eventually flows into the small intestine.

ORGANS: THE ESOPHAGUS

Bolus = chewed clump of food

Esophagus = tube that connects the mouth to the stomach and also begins the process of peristalsis.

Peristalsis: The movement of food down the digestive tract by waves of muscle contractions

Controlled by smooth muscle!

PERISTALSIS

ORGANS: THE STOMACHStomach = a thick-walled muscular sac that

contains enzymes and gastric juices (HCl).Contains 3 smooth muscle layers that alternate

contracting Solids are broken down into a thin, soupy

liquid called chyme.

The enzyme Pepsin breaks down proteins in the stomach into smaller polypeptide fragments

THE STOMACH

ORGANS: SMALL INTESTINE Coiled tube about 20 ft. long and 2.5

cm. in diameter. 1st part = duodenum, where digestive

enzymes enter intestine

Most digestion and ALL nutrient absorption is completed here.

Lined with millions of tiny “fingers” called villi which increase surface area and aide in absorption of nutrients.

SMALL INTESTINAL ENZYMES

Amylase, Maltase, Sucrase, LactaseContinued breakdown of starches

Trypsin, PeptidaseContinued breakdown of proteins

LipaseBreakdown of fats

ORGANS: LARGE INTESTINE

Tube about 5 ft. long and 6 cm. in diameter…No digestion occurs here!Contains many bacteria!

Functions:Reabsorption of waterReabsorption of vitamins (K and B)

created by E. coli bacteria!Elimination of feces through the anus

(stored in rectum)

INSIDE THE LARGE INTESTINE

OTHER IMPORTANT ORGANS

Liver: gland that produces bile which breaks down fat in the small intestineLocated above, right of stomachProduces sodium bicarbonate

(neutralizes HCl)

Gall Bladder: Stores bile

Pancreas: Releases enzymes into the small intestine.Produces hormones that regulate blood

sugar!

CHAPTER 38.3:EXCRETION

CONCEPTS- Structures and Functions- Importance to the Body

EXCRETION - DEFINED

Excretion:The process by which the skin, lungs,

and kidneys remove metabolic wastes and other excess substances from the body

Humans excrete: water, urea (toxic), salts, proteins, sugars, carbon dioxide, etc…

THE ROLE OF THE LIVER

The liver not only produces bile, but has 2 other major functions:1) Detoxification

Usually of alcohol and drugs

2) Formation of UreaThe liver converts Amino acids from broken down proteins into other compounds

The liver takes potentially poisonous compounds and turns them into urea, which will be removed from bloodstream by kidneys

A NORMAL LIVER

CIRRHOSIS OF THE LIVER

THE URINARY SYSTEM

Kidneys: Produce urineUreters: Tubes that carry the urine

down to the…Bladder: Storage chamber for urineUrethra: Tube that urine travels

through to exit the body

THE URINARY SYSTEM

KIDNEY FUNCTIONThe kidneys play an important role in maintaining homeostasis…

They can filter all blood in your body in 45 minutes!

They regulate the blood’s:Water ContentVolumepHWaste Products

Kidneys remove urea, wastes from blood, and send them to the ureter

KIDNEY STRUCTURE

Two major parts:The outer region is the CortexThe inner region is the Medulla

The real work of the kidneys (the filtering of blood) is done by structures called nephrons (area with arterioles & venules).

Each kidney has about 1.25 million nephrons!

KIDNEYS CONTINUED… Location

Either side of the spine, lower back

Ureter: tube that leaves the kidneys carrying urine to the urinary bladderUrinary bladder: stores

urine prior to excretion, which occurs through the urethra

Nephrons: processing units that do the “actual” filtering of the blood

STRUCTURE OF THE KIDNEY

THE NEPHRON

The nephron is composed of a group of capillaries called the Glomerulus surrounded by the Bowman’s capsule.

GLOMERULUS/BOWMAN’S CAPSULE

THE NEPHRON, CON’T

Wastes are filtered through the glomerulus into the Bowman’s capsule, down the loop of Henle, and eventually out of the kidney…

THE ROLE OF THE LUNGS

Considered excretory organs because they remove carbon dioxide and water from the body…

THE ROLE OF THE SKIN

The skin has two layers that contain:Sweat and oil glands, hair, blood vessels,

and fatty tissue…

Functions include:ProtectionExcretion of water, urea, salts, and heat