Physiology Unit

Organic – carbohydrates (simple sugars, starches, fiber), proteins, fats, vitamins  
Inorganic – water, minerals

 Digestive System

• Function – break down food to a usable form (which is small enough to be absorbed into bloodstream and pass through cell membranes)
• Ingestion à Digestion à Absorption of usable materials,  or Egestion of unusable materials (ex. fiber)
• Mouth à pharynx à esophagus à stomach à small intestine à large intestine à rectum à anus
• Accessory structures – food doesn’t enter, but produce enzymes or chemicals which assist in digestion, salivary glands, the pancreas, and liver

 Increasing surface area

• mechanical digestion by teeth and stomach  - for enzyme action
• bile (produced by liver) – acts like a detergent, dissolving and dispersing fat molecules  -for enzyme action
• villi – for absorption into bloodstream from s.i.

Digestive Enzymes
Site	Enzyme	Role in Digestion
Mouth	Salivary Amylase	Starchesàdisaccharides
Stomach	Pepsin	Proteins àlarge peptides
Small Intestine (from pancreas)	Amylase	Continues breakdown of starch
	Trypsin	Continues breakdown of proteins
	Lipase	Breaks down fats
Small Intestine	Maltase, sucrase, lactase	Disaccharides à monosaccharides
	Peptidase	Dipeptides à amino acids

. Function

• Excretion – removal of metabolic end products that are otherwise toxic to system
• Metabolism – all the life functions, all chemical and biological reactions – synthesis, respiration, hydrolysis, neutralization reactions
• MAINTAIN HOMEOSTASIS BY PREVENTING EXCESS BUILDUP OF TOXIC WASTES

II. Structures

A. Skin

B. Liver

C. Lungs

D. Kidneys

LAYERS OF THE KIDNEY

 

#1 - the CORTEX.
 §         jam-packed with lots & lots of those nephrons

§         filtering layer of the kidney.

#2 - the MEDULLA. §         middle layer

§         collecting layer.

§         Tubes carrying filtered wastes travel from the cortex, through the medulla towards the pelvis.

#3 - the PELVIS. §         area where all of the collecting tubules come together & connect with the ureter (which is structure #4).

§          ureter transports the wastes (urine) to the urinary bladder.

THE NEPHRON - the structural units of the Kidney  

• Blood is carried to the kidneys by the renal arteries, which branch into smaller arteries inside the cortex and th en lead to clusters of capillaries called  glomeruli.

§         Each glomerulus is surrounded by a "C"-shaped structure called the Bowman's Capsule.  It is here that materials such as urea, salts, water, glucose, & others pass from the blood into the nephron.

§         These materials (referred to as the "filtrate") pass through the tubule, also known as the loop of Henle.  As the filtrate travels through the tubule, useful substances are reabsorbed into the surrounding capillaries (which connect to veins that will transport the "clean" blood back to the heart via the renal vein).

§         About 180 liters of filtrate is produced each day, but only 1.5 liters of urine.  So as you can see, most materials that initially enter the nephron are reabsorbed, leaving only the urea, salts, & some water in the tubule. 

§         These metabolic wastes form urine, which is transported to the urinary bladder by the collecting tubule.