C HAPTER 38: T HE D IGESTIVE AND E XCRETORY S YSTEMS CONCEPTS - Organs - Functions

animation

O RGANS : T HE M OUTH 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 digestion Saliva: moistens food (easier to chew/swallow) Chemical digestion: enzymes

C OMPONENTS OF THE D IGESTIVE S YSTEM C ONTINUED … Stomach: continues the mechanical and chemical digestion of food Chemical 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.

O RGANS : T HE E SOPHAGUS 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!

P ERISTALSIS

O RGANS : T HE S TOMACH Stomach = 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

T HE S TOMACH

O RGANS : S MALL I NTESTINE Coiled tube about 20 ft. long and 2.5 cm. in diameter. 1 st 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.

S MALL I NTESTINAL E NZYMES Amylase, Maltase, Sucrase, Lactase Continued breakdown of starches Trypsin, Peptidase Continued breakdown of proteins Lipase Breakdown of fats

O RGANS : L ARGE I NTESTINE Tube about 5 ft. long and 6 cm. in diameter… No digestion occurs here! Contains many bacteria! Functions: Reabsorption of water Reabsorption of vitamins (K and B) created by E. coli bacteria! Elimination of feces through the anus (stored in rectum)

I NSIDE THE L ARGE I NTESTINE

O THER I MPORTANT O RGANS Liver : gland that produces bile which breaks down fat in the small intestine Located above, right of stomach Produces sodium bicarbonate (neutralizes HCl) Gall Bladder : Stores bile Pancreas : Releases enzymes into the small intestine. Produces hormones that regulate blood sugar!

C HAPTER 38.3: E XCRETION CONCEPTS - Structures and Functions - Importance to the Body

E XCRETION - D EFINED 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…

T HE R OLE OF THE L IVER The liver not only produces bile, but has 2 other major functions: 1) Detoxification Usually of alcohol and drugs 2) Formation of Urea The 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 N ORMAL L IVER

C IRRHOSIS OF THE L IVER

T HE U RINARY S YSTEM Kidneys: Produce urine Ureters: Tubes that carry the urine down to the… Bladder: Storage chamber for urine Urethra: Tube that urine travels through to exit the body

T HE U RINARY S YSTEM

K IDNEY F UNCTION The 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 Content Volume pH Waste Products Kidneys remove urea, wastes from blood, and send them to the ureter

K IDNEY S TRUCTURE Two major parts: The outer region is the Cortex The 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!

K IDNEYS CONTINUED … Location Either side of the spine, lower back Ureter: tube that leaves the kidneys carrying urine to the urinary bladder Urinary bladder: stores urine prior to excretion, which occurs through the urethra Nephrons: processing units that do the “actual” filtering of the blood

S TRUCTURE OF THE K IDNEY

T HE N EPHRON The nephron is composed of a group of capillaries called the Glomerulus surrounded by the Bowman’s capsule.

G LOMERULUS /B OWMAN ’ S CAPSULE

T HE N EPHRON, CON ’ T Wastes are filtered through the glomerulus Wastes are filtered through the glomerulus into the Bowman’s capsule, down the loop of Henle, and eventually out of the kidney…

T HE R OLE OF THE L UNGS Considered excretory organs because they remove carbon dioxide and water from the body…

T HE R OLE OF THE S KIN The skin has two layers that contain: Sweat and oil glands, hair, blood vessels, and fatty tissue… Functions include: Protection Excretion of water, urea, salts, and heat