Chapter 49: Digestive and Excretory Systems

Chapter 49: Digestive and Excretory Systems

49-1 Nutrients

49-2 Digestive System

49-3 Urinary System

I. Six Basic Food Ingredients• MOST foods contain a bulk of just ONE or TWO nutrient types.

49-1 Nutrients

(1) Nutrients (2 CLASSES: (1) Organic (CPLV) (2) inorganic (MW)• Chemicals NEEDED for growth, maintenance, and metabolic activity.

(1) In some countries, many children suffer from a type of malnutrition called “kwashiorkor.” Symptoms include swollen stomachs and a tendency to become increasingly thinner until they die. Even when provided with RICE and WATER, these children still cannot survive. What TYPE of nutritional deficiency might these children possess?

Critical Thinking

(A) Carbohydrates (e.g., mono-, di-, and polysaccharides)• Broken down (hydrolysis) to monosaccharides (glucose) to be used by cells during AEROBIC RESPIRATION to make ATP.

(B) Proteins (e.g., keratin, polymerase, collagen, hemoglobin, lactase)• Help with growth, reproduction, repair, and ALSO serve as ENZYMES (chemical reactions) [NOTE: essential and non-essential AA].

(C) Lipids (e.g., oils, waxes, saturated and unsaturated fats)• Cell MEMBRANE repair, insulation, protective padding, and serve as an NRG reserve (adipose tissue).

(D) Vitamins (e.g., Vitamin D is the only one self-synthesized)• Large, ORGANIC compounds work as COENZYMES activate true enzymes during our METABOLISM.

(E) Minerals (e.g., calcium, iron, potassium, phosphorous, salts, iodine, zinc)• INORGANIC substances needed for HEALTHY cellular functioning.

Food 2

Food 3

(2) Which of the SIX basic nutrients might a person need to RESTRICT after an operation to REMOVE the gall bladder? Explain your choice.

Critical Thinking

(F) Water• MEDIUM for cellular RXNS, PLASMA (blood pressure), and used to REGULATE body temperature (heating/cooling).

(1) Dehydration (NOTE: A 12% loss = fatal)• If water is LOST (and NOT replenished), then water will be DRAWN from ECM to blood (via osmosis)—eventually cells lose water AND die.

I. The Gastrointestinal Tract (a.k.a., alimentary canal)• G.I. TUBE mouth TO anus (excludes ACCESSORY organs liver and pancreas).

49-2 The Digestive System

(A) Mouth• Mechanical (mastication) AND chemical digestion (salivary amylases).

(1) Incisors and Molars• EXPOSE larger SURFACE AREA for enzymes to ACT UPON.

(2) Hard Palate and Soft Palate (UPPER MOUTH)• Bony region (FRONT), grinds food AGAINST; SOFT tissue (BACK) separates mouth from NASAL cavity.

(3) Saliva (i.e., water, mucus, and amylase—breaks down STARCHES)• SOFTENS food for swallowing AND assists with digestion.

(B) Esophagus (i.e., food pipe; circular AND longitudinal smooth muscle)• Delivers BOLIS (via peristalsis) from oral cavity TO stomach.

(1) Bolis (i.e., food BALL)• Once chewed and moistened, food is ROLLED into a swallow-able ball.

(2) Epiglottis (separates esophagus-trachea)• Flap of cartilage PREVENTS material from entering TRACHEA.

(3) Peristalsis (carried out by TWO smooth muscle types)• Involuntary, muscular CONTRACTIONS squeeze bolis through a VALVE into stomach. (NOTE: defies gravity)

(C) Stomach (made of circular, longitudinal, AND diagonal smooth muscles)• Elastic, muscular sac MAXIMIZING mechanical (churning) and chemical (digestive acids) digestion [3-4 hours per meal].

(1) Gastric Pits (open ends of GASTRIC GLANDS lining the stomach)• Secrete MUCUS, digestive ENZYMES, and HCl mix to produce an ACIDIC fluid (pH < 2).

II. Chemical Digestion• Amylase (saliva), HCl (stomach), pepsin (stomach), other enzymes (intestines)—liberate nutrients, allow for ABSORPTION into bloodstream.

(3) Some people CANNOT drink milk because they are unable to digest LACTOSE, the sugar in milk. Doctors believe this inability involves SPECIFIC areas of the digestive system. What do you suppose these areas are?

Critical Thinking

(1) Gastric Fluid (i.e., product of gastric pits)• Responsible for CHEMICAL digestion in stomach (enzymes and acid).

(2) Pepsin (NOTE: Converted from inactive pepsinogen (needs LOW pH)• Enzyme SPLITS large PROTEINS into SMALLER chains of amino acids (peptides).

(3) Ulcer (lesions recently attributed to some H. pylori bacteria species)• Mucous coating BREAKS down, allowing gastric fluid to DIGEST part of stomach epithelial lining.

(A) Formation of Chyme• Mouth Esophagus Cardiac Sphincter Stomach Pyloric Sphincter CHYME enters INTESTINES.

(1) Cardiac Sphincter (circular muscle BETWEEN esophagus and stomach)• Regulates what ENTERS or LEAVES stomach from esophagus.

(2) Chyme• INTESTINAL PASTE of fats, sugars, starches, vitamins, minerals, peptides, and proteins (that were NON-affected by pepsin).

(3) Pyloric Sphincter (circular muscle between stomach AND small intestine)• Regulates FLOW of chyme into SMALL INTESTINE mixes with SECRETIONS from LIVER and PANCREAS.

II. Liver (NOTE: Largest GLAND in the body)• Makes BILE (emulsifies NOT digests fats), stores GLYCOGEN, and breaks down TOXINS in blood into harmless products (alcohol, ammonia).

(1) Gall Bladder (NOTE: Cholesterol deposits can lead to “GALLSTONES”)• EXPANDS and STORES BILE to be secreted into S.I. during CHYME movement.

(C) Pancreas (digestive AND endocrine organ, sodium bicarbonate, raises pH)• Secretes fluid RAISES pH of chyme from acid TO base—activates DIFFERENT enzymes inside intestine.

(4) A person has a small intestine that has villi BUT lacks microvilli. Would you expect this person to be underweight OR overweight? Explain.

Critical Thinking

(D) Small Intestine (i.e., duodenum-jejunum-ileum ~22 feet long coil)• FINAL site of digestion and where NUTRIENT ABSORPTION into bloodstream is MAXIMIZED (e.g., villi and microvilli).

(1) Jejenum (MIDDLE section, ~ 8 feet long)• Mucus PROTECTS intestinal walls from protein-digesting enzymes.

(E) Absorption (large SURFACE AREA for nutrients)• AA, glucose, and fatty acids are absorbed into BLOOD and LYMPHATIC vessels lining small intestine.

(1) Villi and Microvilli (fingerlike PROJECTIONS of intestinal lining)• INCREASE surface area of 21 FEET of intestines to SIZE of roughly a TENNIS COURT (absorb via diffusion and active transport).

(2) Lacteals (tiny LYMPH capillaries)• LYMPH receives FATS eventually to bloodstream; BLOOD receives AA and SUGARS liver FILTERS nutrient rich blood.

III. Large Intestine (4 regions: ascending, transverse, descending, sigmoid)• Only minerals AND vitamins (bacteria made) and WATER are reabsorbed into bloodstream; ELIMINATE feces, (solid remains of CHYME).

Food 2

Food 3

I. Kidneys (maintain HOMEOSTASIS of body)• Regulating PRESSURE and pH of blood (water volume and solutes).

49-3 Urinary System

(A) Structure (paired organ)• Kidney is subdivided into (1) CORTEX and (2) MEDULLA

(1) Cortex and Medulla• OUTER (1/3) and INNER (2/3) regions of kidney.

(2) Renal Pelvis (EXTENSION of the ureter)• Funnel-shaped structure in CORE of kidney (acts as a CHANNEL).

(3) Urea (product of PROTEIN metabolism)• Nitrogenous waste product brought to liver as AMMONIA.

(4) Ammonia• Removed from blood by liver and CONVERTED to urea, which enters bloodstream and is REMOVED by kidneys.

(5) When the kidneys stop functioning, urea builds up in the blood and poisons the body. A person with kidney failure will eventually die if the urea is not somehow removed. For the urea to be removed, the patient must be attached to an “artificial kidney,” also called a dialysis machine. Using your understanding of how a normal kidney functions, what do you suppose this machine is built to do/regulate?

Critical Thinking

(B) Nephron (~ 1 MILLION per kidney, perform ALL duties for urine)• Functional unit of kidneys (Filtration, Reabsorption, & Secretion)

(1) Urine (a mixture of products)• Removed FROM blood (includes urea, water, toxins, & mineral salts).

(6) Explain why a high concentration of protein in the urine may indicate damaged kidneys.

Critical Thinking

(2) Bowman’s Capsule (CUP-shaped structure)• Encloses a CAPILLARY bed (i.e., glomerulus) where HIGH pressured “DIRTY” blood is RECEIVED (from the renal ARTERY).

(3) Glomerulus (enclosed INSIDE Bowman’s Capsule; 125 mL/minute)• CAPILLARY BED that receives dirty blood from renal artery (FILTER).

(4) Renal Tubule [PCT, Loop of Henle, DCT]• A long TUBE with PERMEABLE walls in nephron.

(C) Filtration (FORCES out: urea, water, glucose, vitamins, and salts) • Materials from blood are forced OUT of glomerulus into Bowman’s Capsule.

(D) Reabsorption and Secretion• Materials RETURN to blood (ACTIVE transport) OR some materials PASS from blood to FILTRATE (secretion)

(1) Reabsorption (MOST occurs in PCT, some in DCT)• 75% of WATER (in filtrate) returns BACK to BLOOD, in addition glucose and minerals ALSO returned to BLOOD.

(2) Secretion (when FILTRATE reaches the DCT)• Wastes moved from BLOOD to FILTRATE, in addition, pH of the blood is ADJUSTED by secreting excess H+ ions.

(7) The loop of Henle functions to conserve water by reabsorbing it. Its length varies among mammal species. Would you expect the loop of Henle of an animal like a dolphin to be longer or shorter than that found in humans? Explain.

Critical Thinking

(E) Formation of Urine• Fluids and wastes that REMAIN in DCT form URINE that flows into a COLLECTING DUCT (via osmosis).

(F) The Loop of Henle (between PCT and DCT)• Maintains a HIGH [NaCl] in SURROUNDING fluid, driving water (via OSMOSIS) out of collecting duct (and BACK to the BLOOD).

(G) Elimination of Urine• Urine from COLLECTING DUCTS drains into RENAL PELVIS and into a narrow tube (ureter).

(1) Ureter (1 for EACH kidney)• Drains renal pelvis into URINARY BLADDER for storage of urine.

(2) Urinary Bladder (1 for BOTH kidneys)• Muscular EXPANDABLE sac drains into urethra.

(3) Urethra (1 for BOTH kidneys)• Tube EXITING urine from BODY.

(H) Excretory System (AIM: To eliminate WASTES from healthy cells)• Includes kidneys, skin, and lungs, tightly tied into CIRCULATORY system.