• Food: source of energy and essential molecules

• optimal diet: more carbohydrates than fats and significant of protein

DIGESTION

• Carbohydrates: cereals, grains, breads– 4 calories per gram

• fats: oils, margarine, butter, fried foods, meats, snack foods– 9 cal/gram

• Proteins: poultry, fish, meat– 4 cal/gram

• Fiber: part of plant cannot be digested by humans– diets low in fiber result in a slow passage of food through

the colon, associated with colon cancer

• essential minerals: calcium, phosphorous, iron• Essential vitamins: vit A, B, D, C

A healthful diet satisfies three needs:

– Fuel for an organism’s activities

– Raw materials for biosynthesis

– Essential nutrients

– Vegetarians must be sure to obtain all eight essential amino acids

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Obesity is a human health problem:

– usually caused by lack of exercise and abundance of fattening foods

– May partly stem from an evolutionary advantage of fat hoarding

• Research on mice: Has shown that a defect in the gene for leptin may cause obesity

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• wealthy countries: overweight 65%• body mass index (BMI): estimate of body weight in kg, divided by height in meters2

DIGESTIVE SYSTEM

• alimentary canal: separate mouth and anus to transport of food is one way

• physical forces, chewing and grinding, first breaks the ingested food into smaller fragments

• chemical digestion, hydrolysis reactions that liberate the subunits

• products of digestion are transported by the blood• molecules not absorbed are excreted

• digestive system parts:– gastrointestinal

tract– accessory organs

Digestion begins in the oral cavity

• Teeth: break up food

• omnivores teeth are specialized for eating both plant and animal material: Carnivores: front of the mouth, Herbivores: in the back

• children have only 20 teeth/// Adults: 32 adult

• Saliva: moistens it

• salivary enzymes begin the hydrolysis of starch

• Tongue: pushes the bolus of food into the pharynx

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Teeth

IncisorsCanine

PremolarsMolars

Tongue

Salivaryglands

Opening of asalivary gland duct

The food and breathing passages both open into the pharynx

– food is prevented from going into the respiratory tract by the epiglottis

The swallowing reflex: Moves food from the pharynx into the esophagus, while keeping it out of the trachea

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Tongue

Pharynx

Larynx

Trachea (windpipe)Esophagus

Esophagealsphincter

Epiglottisup

Bolus of food

Sphincter contracted Sphincter relaxed Sphincter contracted

Epiglottisdown

Larynxup

Esophagus

Epiglottisup

Larynxdown

The esophagus squeezes food along to the stomach by peristalsis

food from the esophagus into the stomach is controlled by a ring of muscle, sphincter

- when relaxed>>> stomach contents can be brought back out during vomiting and lead to acid reflux or heartburn

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Bolus offood

Muscles relax,allowing passagewayto open

Stomach

Musclescontract,constrictingpassagewayand pushingbolus down

Muscles contract

Muscles relax

Muscles contract

Musclesrelax

The Heimlich maneuver can save lives: dislodge food from the pharynx or trachea during choking

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• Stomach:– saclike smooth muscle for churning food– Substances release:

• gastric juice • hydrochloric acid (HCl) with low pH to denature proteins and kill

bacteria• pepsin for digestion of proteins

Bacterial infections, Helicobacter pylori, in the stomach and duodenum are associated with ulcers

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• Intestines– Types:

• Small: carbohydrates, protein, and lipids are broken down and absorbed into the bloodstream

• Large: production of waste or feces

• small intestine:– Parts:

• Duodenum: first part where “real” digestion and absorption of food is done

• Jejunem: digestion continues• Ileum: water and digested products

are absorbed

• Folds of the intestinal lining, and tiny, fingerlike villi: Increase the absorptive surface

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1

• large intestine – wider diameter than the small intestine– no digestion takes place here– Main functions:

• fluid absorption from waste: water, Na, vitamin K• compact and store undigested material as feces in

the rectumLargeintestine(colon)

Sphincter

Endof smallintestine

Appendix

Cecum

Anus

Rectum

Smallintestine

Nutrientflow

The small intestine is the major organ of chemical digestion and nutrient absorption in which 2 major organs secrete their content:

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Liver

Gall-bladder

Intestinal enzymes

Duodenum ofsmall intestine

Bile

Bile

Acid chyme

Pancreaticjuice

Stomach

Pancreas

• pancreas– Secretes bicarbonate

to neutralize the acid chyme

– And enzymes to digest food polymers

• trypsin, chymotrypsin digest proteins

• amylase digests starch• lipase digests fats

– Also produces hormones: insulin and glucagon to deal with glucose storage

Liver

Intestines

Kidneys

HepaticPor talvein

• liver – largest internal organ

– has a strategic location in the body: between the intestines and the hear

– Many functions:

• produces bile and stores it in the gallbladder for fat digestion

• removes toxins, pesticides, carcinogens and other poisons by converting them into less toxic forms

• produces urea

• Breaks down toxins

Alcohol consumption can damage the liver and liver function can be impaired, as well as hepatitis

EXCRETORY SYSTEM

Major parts:• Kidneys, 2 kidneys,

each of contains 1 mll nephrons

• ureter• urinary bladder• Urethra

Functions: major role in homeostasis>>> expels wastes and regulates water and ion balance

• Nephrons, the functional units of the kidneys>>> Extract a filtrate from the blood and refine it to urine>>>Urine leaves the kidneys via ureters>>>Is stored in the urinary bladder, and is expelled through the urethra

Aorta

Inferiorvena cavaRenal artery and vein

Ureter

Urinary bladderUrethra

A The excretory system

Kidney

Renal cortexRenal medulla

Renal pelvis

Ureter

B The kidney

Bowman’scapsule

C Orientation of a nephron within the kidney

Renal artery

Renal vein

Nephrontubule

Collectingduct

Torenalpelvis

Renal cortex

Renal medulla

Glomerulus 1 Proximal tubule

3 Distal tubule

Capillaries

Fromanothernephron

Collectingduct

Bowman’s capsule

Arteriolefrom renalartery

Arteriolefromglomerulus

Branch ofrenal vein

2 Loop of Henle with capillary network

D Detailed structure of a nephron

– Major processes of the excretory system

H2O, other small molecules Urine

ExcretionSecretionReabsorptionFiltration

CapillaryInterstitial fluid

Nephron tubule

The key processes of the excretory system are filtration, reabsorption, secretion, and excretion

• In filtration: Blood pressure forces water and many small solutes into the nephron

• In reabsorption: Valuable solutes are reclaimed from the filtrate

• In secretion: Excess H+ and toxins are added to the filtrate

• The product of all of the above processes is urine: Which is excreted

Kidney dialysis can be a lifesaver

– Compensating for kidney failure

– A dialysis machine removes wastes from the blood and maintains its solute concentration

Line from arteryto apparatus

Dialyzingsolution

Fresh dialyzingsolution

Used dialyzing solution(with urea and excess ions)

Tubing made of a selectively permeablemembrane

Pump

Line fromapparatusto vein