Ch 34 & 35 lecture

Copyright © 2009 Pearson Education, Inc..

Lectures by

Gregory AhearnUniversity of North Florida

Chapter 34-35

Nutrition, Digestion, and

Excretion

Copyright © 2009 Pearson Education Inc.

34-35.1 How Do Animals Regulate The Composition Of Their Bodies? A nutrient is any substance that an animal

needs but cannot synthesize or produce in its own body, and hence must acquire it from its environment as it eats or drinks.

Digestion is the process whereby an animal physically grinds up and chemically breaks down its food, producing small, simple molecules that can be absorbed into the circulatory system.


34-35.1 How Do Animals Regulate The Composition Of Their Bodies? Nutrition includes taking food into the body,

converting it into usable forms, absorbing the resulting molecules from the digestive tract into the circulatory system, and using the nutrients in the animal’s own metabolism.

Excretion is the disposal of indigestible, toxic, or surplus materials.


34-35.2 What Nutrients Do Animals Need?

Animal nutrients fall into six major categories:• Lipids• Carbohydrates• Proteins• Minerals• Vitamins• Water



The primary sources of energy are lipids and carbohydrates.• Energy is provided mostly from lipids,

carbohydrates, and to lesser extent, proteins.• Energy in food is measured in Calories.• A Calorie is the amount of energy needed to

raise the temperature of 1 gram of water by 1 degree Celsius.

• The average person at rest burns 1,550 Calories per day at rest.





Lipids include fats, phospholipids, and cholesterol.• Fats and oils are used primarily as a source of

energy.• Cholesterol is used to make cell membranes

and several hormones, including testosterone and estrogen.

• Essential fatty acids, such as linoleic acid, cannot be synthesized and must be obtained in the diet.



Fats store energy in concentrated form.• In humans, energy is stored primarily as fat.• When more Calories are eaten than are used,

the excess fats, carbohydrates, and proteins are all converted to fat for storage.

• Fats has twice as much energy per unit weight as the other nutrients.

• Lipids are hydrophobic and do not cause water to be accumulated within the fats in the body.



For example, the ruby-throated hummingbird migrates across the Gulf of Mexico in the fall, getting its energy from stored lipids.

Fig. 34-35-1



Carbohydrates are a source of quick energy.• Carbohydrates include simple sugars and

longer chains of sugars called polysaccharides.

• During digestion, simple sugars, like glucose, are derived from the breakdown of more complex carbohydrates, such as sucrose and starch.

• Animals and humans store sugars as glycogen, a large branched chain of glucose molecules.



Proteins provide amino acids for building new proteins.• Protein provides these amino acids after they

are digested.• Dietary protein comes from meat, milk, eggs,

corn, and beans.• Our bodies can synthesize certain amino

acids, but eight cannot be made by our biochemistry and must be supplied in our diet—they are called “essential amino acids”.



Protein deficiency can cause a variety of debilitating conditions, including kwashiorkor.

Fig. 34-35-2



Minerals are elements required by the body.• A mineral is a chemical element that is

required for proper bodily function.• Minerals are needed for strong bones and

teeth, for muscles contraction, for nerve functions, and for proper blood cell functions.

• Metals are also important since they act as parts of enzymes in certain body reactions (e.g., zinc, copper, selenium).




Vitamins play many roles in metabolism.• Vitamins are a diverse group of organic

compounds that animals require in very small amounts.

• The body cannot synthesize them, so they must be obtained in the diet.

• Vitamins are grouped into two categories: water soluble and fat soluble.





Water-soluble vitamins• These substances dissolve in water or blood

plasma and are excreted by the kidney; they therefore do not build up in the body.

• They include vitamin C and the B-vitamin complex.



A deficiency in niacin, a B-vitamin, causes cracked, scaly skin and digestive and nervous system disorders.

Fig. 34-35-3



Fat-soluble vitamins• Fat soluble vitamins can accumulate in the

body and be toxic if present in too high a concentration.

• This group includes:• Vitamin K: regulates blood clotting• Vitamin A: produces visual pigments in the

eyes for vision• Vitamin D: promotes strong bones• Vitamin E: prevents cellular damage; is an

antioxidant



Vitamin D deficiency can lead to a condition called Rickets, which is a deterioration of bone.

Fig. 34-35-4



The human body is about two-thirds water.• Water is the principal component of saliva,

blood, lymph, extracellular fluid, and cytoplasm within each cell.

• The average human requires about 2,500 milliliters (10 cups) of water per day, but this can change with exercise, temperature, and humidity.

• We obtain about half of our water from the food we eat and the rest is obtained from the fluids we drink.



Nutritional guidelines help people obtain a balanced diet.• Nutritional guidelines, called “My Pyramid,”

are posted to a U.S. government interactive website.

• Other sources of nutritional information are found on the labels of commercially packaged foods; they contain information about calorie, fat, sugar, and vitamin content.



Are you too heavy?• A simple way to calculate whether your

weight is likely to pose a health risk is to calculate your body mass index (BMI).

• The BMI takes into account your weight and height to arrive as an estimate of body fat.

• Two ways to calculate your BMI are:

1. Weight (in kilograms)/height2 (in meters)

2. Weight (in pounds) x 703/height2 (in inches)



Are you too heavy? (continued)• A BMI between 18.5 and 25 is considered

healthy.• People with anorexia have a BMI of 17.5 or

lower.• A BMI between 25 and 30 indicates you are

probably overweight.• A BMI over 30 indicates your are obese.


34-35.3 What Are The Major Processes Of Digestion? All digestive systems must accomplish

certain tasks.• Ingestion: food is brought into the digestive

tract through the mouth• Mechanical breakdown: the physical

breakdown of food into small pieces• Chemical breakdown: digestive enzymes

convert the large molecules in food into small molecules


34-35.3 What Are The Major Processes Of Digestion? All digestive systems must accomplish

certain tasks (continued).• Absorption: the transfer of small molecules

across the gut to the blood and then to cells of the body

• Elimination: indigestible materials are expelled from the body


34-35.4 What Is The Diversity Of Digestive Systems In Non-Human Animals? In sponges, digestion occurs within single

cells.• Sponges rely exclusively on individual cells to

digest their food.• Sponges circulate seawater through pores in

their bodies, and collar cells filter microscopic organisms from the water and ingest them by phagocytosis.

• Phagocytized food is digested inside these cells in sacs called lysosomes, which contain digestive enzymes.


34-35.4 What Is The Diversity Of Digestive Systems In Non-Human Animals? Intracellular digestion in a sponge

Fig. 34-35-6

H2O carryingfood particlesenters the pores

Food particlesare filtered from thewater by the collar

Food enters thecollar cell by phagocytosis,forming a food vacuole

Waste products areexpelled by exocytosis

Water, uneaten food,and wastes are expelledthrough the large openingat one end of the sponge

collar cell

H2O

H2O

lysosomewithdigestiveenzymes

food vacuole

The foodvacuole mergeswith a lysosome

H2O

H2O

A simple sponge

Tube sponges

Collar cell(b)

(a)

(c)


34-35.4 What Is The Diversity Of Digestive Systems In Non-Human Animals? Jellyfish and their relatives have digestive

systems consisting of a sac with a single opening.• The most simple digestive tract occurs in sea

anemones, coral, and jellyfish, which possess a sac with one opening.

• Both food and waste pass through the single opening.

• Food is chemically broken down in the sac by digestive enzymes, and the nutrients are absorbed by cells lining the sac.


34-35.4 What Is The Diversity Of Digestive Systems In Non-Human Animals? Digestion in a sac

Fig. 34-35-7

Tentacles withstinging cells capturethe prey and carryit into the mouth

Gland cells secretedigestive enzymes intothe digestive sac andbegin extracellulardigestion

Nutritive cells engulffood particles andcomplete digestionwithin food vacuoles

mouth

prey

prey

digestivesac

Hydra with prey

Food processing in Hydra

(a)

(b)


34-35.4 What Is The Diversity Of Digestive Systems In Non-Human Animals? Most animals have digestive systems

consisting of a tube with several specialized compartments.• The tube performs different functions along its

length; food is first mechanically broken down, then chemically altered, then the nutrients are absorbed, and finally, wastes are eliminated.


34-35.4 What Is The Diversity Of Digestive Systems In Non-Human Animals? Worms, mollusks, arthropods, and

vertebrates are examples of animals with this type of gut.

Fig. 34-35-8

anus

intestine

pharynx

esophagus

mouth

crop gizzard

Soil withfood particlesis ingested

Indigestible remnantsare expelled

Food is digestedand absorbed in theintestine

Food is groundup in the gizzard


34-35.5 How Do Humans Digest Food?

Humans have a tubular digestive tract with several compartments in which food is broken down, physically and chemically, before being absorbed into the circulatory system.

Digesting and absorbing food requires coordinated action from the various structures of the digestive system.

Copyright © 2009 Pearson Education Inc.Fig. 34-35-9

Oral cavity. tongue,teeth: Grind food,mix with saliva

Stomach: Breaksdown food andbegins proteindigestion

Small intestine:Food is digestedand absorbed

Rectum: Stores feces

Salivary glands: Secretelubricating fluid andstarch-digesting enzymes

Pharynx: Shared digestiveand respiratory passage

Epiglottis: Directs fooddown the esophagus

Esophagus: Transportsfood to the stomach

Liver: Secretes bile (alsohas many non-digestivefunctions)

Gallbladder: Stores bilefrom the liver

Pancreas: Secretes buffersand several digestiveenzymes

Large intestine: Absorbsvitamins, minerals, andwater; houses bacteria;produces feces



Breakdown of food begins in the mouth.• Mechanical food breakdown is due to the

action of 32 teeth of different shapes and sizes including incisors, canines, premolars, and molars.

• Three pairs of salivary glands secrete saliva, which lubricates the food, as well as amylase, which starts the chemical breakdown of sugars in the mouth.

Fig. 34-35-10



Teeth begin the mechanical breakdown of food.

Fig. 34-35-10

incisors

canine

premolars

molars



PLAYPLAY Animation—Digestion in the Mouth



The pharynx connects the mouth to the rest of the digestive system.• With the help of the muscular tongue, the food

is manipulated into a mass and pressed backward into the pharynx, which connects the mouth with the esophagus.

• The swallowing reflex elevates the larynx, so that the epiglottis blocks off the opening to the trachea and guides food to the esophagus.


Before swallowing During swallowing

The epiglottis iselevated to allow airto flow through thepharynx into the larynx

The tonguemanipulatesfood whilechewing

Thetongue forcesfood into theesophagus

The larynx movesup and the epiglottisfolds over the larynx

pharynx

epiglottis

esophagus

larynx

roof of mouth

food

tongue

Food entersthe esophagus

food

esophagus

epiglottis

larynx

(a) (b)


The challenge of swallowing

Fig. 34-35-11



The esophagus conducts food to the stomach.• Swallowing forces food into the esophagus, a

muscular tube that propels the food from the mouth to the stomach.

• Muscles surrounding the esophagus produce a wave of contraction, called peristalsis, that begins above the swallowed food and progresses down the esophagus, forcing the food to the stomach.



The stomach stores and breaks down food.• The human stomach is an expandable

muscular sac capable of holding as much as a gallon of food and liquids.

• The stomach has three functions:• It stores food and releases it gradually into

the small intestine for digestion and absorption.

• It assists in the mechanical food breakdown.

• It has a role in chemical food breakdown.



PLAYPLAY Animation—Digestion in the Stomach



Most digestion occurs in the small intestine.• The small intestine is 1 inch in diameter and

10 feet long.• It digests food into small molecules and

absorbs them into the bloodstream.• This process of digestion is accomplished with

the aid of secretions from the liver, the pancreas, and the cells of the small intestine itself.



The liver and gallbladder provide bile.• The liver stores glycogen and detoxifies many

poisonous substances.• It also produces bile for digestion; bile is a

complex mixture of bile salts, other salts, water, and cholesterol.

• Bile is stored in the gallbladder and is released into the small intestine where it aids in fat digestion.



The pancreas secretes digestive substances.• The pancreas consists of two major types of

cells:• One type produces hormones that regulate

blood sugar.• The other type produces a digestive

secretion called pancreatic juice; this contains water, sodium bicarbonate, and several digestive enzymes that break down sugars, lipids, and proteins.



The intestinal wall completes the digestive process.• Digestive enzymes are embedded in the

plasma membrane of the cells that line the small intestine, so that the final phase of digestion occurs as the nutrient is being absorbed into the cell.



Most absorption occurs in the small intestine.• The small intestine is the major site of nutrient

absorption into the blood.• It has numerous folds and projections that

give it an internal surface area 600 times greater than a smooth tube of the same length.

• Fingerlike projections called villi (singular, villus) cover the entire surface of the intestinal wall.



Most absorption occurs in the small intestine (continued).• Each cell on a villus has microscopic

projections called microvilli, which increase the area for absorption even more.

• Within each villus is a network of blood capillaries and a single lymph capillary called a lacteal.

• Most nutrients pass through the cells of the small intestine and enter the capillaries, but breakdown products of fats pass across the cells and enter the lacteals.



The small intestine

Fig. 34-35-12

villi

lacteal

arteriole

lymphvesselvenule

capillaries

microvilli

intestinalgland

fold ofintestinallining

Small intestine A fold of theintestinal lining

A villus Cells of a villus(a) (b) (c) (d)



The large intestine absorbs water, minerals, and vitamins, and forms feces.• The large intestine in an adult human is about

5 feet long and 3 inches in diameter; the first part is called the colon and the last 6 inches is the rectum.

• Bacteria in the colon synthesize vitamin B12, thiamin, riboflavin, and vitamin K.

• Large intestine cells absorb water, minerals, and vitamins.

• Feces is formed in the large intestine.



PLAYPLAY Animation—Digestion in the Intestines



PLAYPLAY Animation—Absorption of Nutrients



Digestion is controlled by the nervous system and hormones.• The secretions and muscular activity of the

digestive tract are regulated by both nerves and hormones.

• Sensory signals initiate digestion.• The sight, smell, taste, and just the thought

of food generate signals from the brain that act on the digestive tract.

• For example, nerve impulses stimulate the salivary glands and cause the stomach to secrete acid and mucus.



Hormones help regulate digestive activity through negative feedback.• Gastrin is secreted from stomach cells in

response to the presence of protein breakdown products, and stimulates acid secretion by the stomach.

• Secretin and cholecytokinin are secreted by the small intestine in response to chyme coming from the stomach; they stimulate the secretion of digestive enzymes and sodium bicarbonate by the pancreas and bile from the liver.



Gastric inhibitory peptide, secreted by the small intestine in response to fatty acids and sugars in chyme, stimulates the pancreas to release insulin.

This in turn stimulates body’s cells to absorb sugar from the blood.

It also inhibits stomach peristalsis, which slows its emptying rate.


34-35.6 What Are The Functions Of Urinary Systems? All urinary systems of animals function

similarly.• First, the blood is filtered, with water and small

dissolved molecules moving from the blood into the urinary system.

• Next, nutrients are selectively reabsorbed back into the blood.

• Some highly toxic substances are actively secreted from the blood into the urinary system.

• Finally, wastes and excess nutrients are excreted from the body.


34-35.7 What Is The Diversity Of Urinary Systems In Non-Human Animals? In a few animals, like sponges, individual

cells dump wastes into the surrounding water.

Most animals have complex urinary systems, under nervous and hormonal control, that regulate which substances are excreted and which are retained in the body’s fluids.

Flame cells are urinary structures in flatworms, while nephridia have the same role in earthworms.


34-35.7 What Is The Diversity Of Urinary Systems In Non-Human Animals? Flame cells filter fluids in flatworms.

• Because flatworms largely live in freshwater, a major function of their excretory system is to regulate water balance.

• The flatworm’s excretory system consists of a network of tubes that branch throughout the body.

• At intervals, the branches end blindly in single-celled bulbs called flame cells.

• Water and dissolved substances are filtered from the body by these bulbs, and are expelled through pores on the body surface.


flamecell

cilia

fluid

tubule

eyespot

excretorypores

34-35.7 What Is The Diversity Of Urinary Systems In Non-Human Animals? The simple

excretory system of a flatworm

Fig. 34-35-13


34-35.7 What Is The Diversity Of Urinary Systems In Non-Human Animals? Nephridia filter fluids in earthworms.

• Earthworms, mollusks, and other invertebrates have simple filtering structures called nephridia, which resemble the filtering structures found in vertebrate kidneys.

• Each segment of the worm contains a pair of nephridia that filter each segment of wastes and nutrients.

• The resulting urine is stored in a bladder-like portion of the nephridium and is excreted through pores in the body wall.


nephridia

intestine

excretory porenerve cord

34-35.7 What Is The Diversity Of Urinary Systems In Non-Human Animals? The excretory

system of the earthworm

Fig. 34-35-14


34-35.8 How Does The Human Urinary System Work? The human urinary system produces,

transports, and excretes urine.• The kidneys are organs in which the fluid

portion of the blood is collected and filtered.• From this fluid, water and important nutrients

are then reabsorbed into the blood.• The remaining fluid, called urine—consisting

of toxic substances, cellular waste products, excess vitamins, salts, some hormones, and water—stays behind and is excreted from the body.


34-35.8 How Does The Human Urinary System Work? The urinary system is crucial for

homeostasis.• It regulates blood levels of ions such as

sodium, potassium, chloride, and calcium.• It regulates the water content of the blood.• It maintains proper pH of the blood.• It retains important nutrients such as glucose

and amino acids in the blood.• It eliminates cellular waste products such as

urea.


ammonia

urea

carriedin blood

carriedin blood

amino acid

In cells, amino acidsare broken into simplermolecules, releasingammonia

In the liver, ammoniais converted to urea

In the kidneys, urea andother water-soluble wastesare filtered from the blood

excretedin

urine

34-35.8 How Does The Human Urinary System Work? A flow diagram

showing the formation and excretion of urea

Fig. 34-35-15


34-35.8 How Does The Human Urinary System Work? The urinary system consists of the kidneys,

ureter, urinary bladder, and urethra.• Human kidneys are paired organs located on

either side of the spinal cord, slightly above the waist.

• The kidneys produce urine, which leaves each kidney through a narrow, muscular tube called a ureter.

• The ureters transport the urine to the urinary bladder.

• The urethra is a short tube from the bladder to the outside world.


34-35.8 How Does The Human Urinary System Work? The human urinary

system

Fig. 34-35-16

left renalartery

left kidney

left renalveinaorta

left ureter

urinarybladder

urethra(in penis)

vena cava


34-35.8 How Does The Human Urinary System Work?

PLAYPLAY Animation—Human Urinary System


34-35.8 How Does The Human Urinary System Work? Urine is formed in the nephrons of the

kidneys.• Each kidney contains a solid outer layer

where urine forms and an inner chamber that collects urine and funnels it into the ureter.

• The outer layer of each kidney contains about a million tiny tubes called nephrons, which filter the blood, process the filtered fluid, and form urine.


34-35.8 How Does The Human Urinary System Work? Cross section of a

kidney

Fig. 34-35-17

renalartery

renalvein

ureter(cut awayto showthe pathof urine)

tobladder

renal pelvis(cut awayto show thepath of urine)

urine

collectingduct

nephron

enlargement of a singlenephron and collecting duct


34-35.8 How Does The Human Urinary System Work? Each nephron has three parts:

• The glomerulus: capillaries from which fluid is filtered from the blood and collected

• Bowman’s capsule: captures filtered fluid from the glomerulus

• The tubule: receives filtered fluid from Bowman’s capsule


34-35.8 How Does The Human Urinary System Work? An individual

nephron and its blood supply

Fig. 34-35-18

collectingduct

distal tubule

proximal tubule

glomerulus

Bowman’scapsule

arterioles

branch ofrenal vein

branch ofrenal artery

loop of Henle

capillaries


34-35.8 How Does The Human Urinary System Work? Different portions of the tubule selectively

modify the fluid as it travels through them; nutrients are selectively reabsorbed, while wastes remain behind to form urine.• The Bowman’s capsule channels fluid into the

proximal tubule.• The fluid then moves through the loop of

Henle and the distal tubule.• The distal tubules of multiple nephrons drain

into a collecting duct that conducts urine to the ureter.


34-35.8 How Does The Human Urinary System Work? Blood is filtered by the glomerulus.

• Urine formation starts with the process of filtration.

• Blood enters each nephron by an arteriole that branches off the renal artery.

• The arteriole branches into capillaries that form the glomerulus.


34-35.8 How Does The Human Urinary System Work? Blood is filtered by the glomerulus (continued).• Blood pressure within the capillaries forces

water and dissolved substances through the wall of the glomerulus.

• The resulting watery fluid is called the filtrate.


34-35.8 How Does The Human Urinary System Work? The filtrate is converted to urine in the

tubules of the nephron.• This filtrate contains a mixture of wastes,

essential nutrients, and water.• The nephron must restore the nutrients and

most of the water to the blood while retaining the wastes for elimination.

• This process is accomplished by the two processes of tubular reabsorption and tubular secretion.


34-35.8 How Does The Human Urinary System Work? Tubular reabsorption moves water and

nutrients from the nephron to the blood.• From Bowman’s capsule, the filtrate passes

through the proximal tubule where most of the water and nutrients in the filtrate move from the proximal tubule into the capillaries; this process is called tubular reabsorption.

• Salts and nutrients are actively transported out of the proximal tubule into the extracellular fluid, and then diffuse into the surrounding capillaries to return to the blood.


34-35.8 How Does The Human Urinary System Work? Tubular secretion moves wastes from the

blood into the nephron.• In tubular secretion, wastes such as hydrogen

ions, potassium, ammonia, and many drugs are moved from the capillaries into the nephron.

• Cells of the distal tubule actively transport wastes from the surrounding extracellular space into the tubule, creating a concentration gradient from blood in the capillaries to the extracellular fluid; the wastes thus diffuse out of the capillaries.


34-35.8 How Does The Human Urinary System Work? Urine becomes concentrated in the

collecting ducts.• Concentration of urine occurs in the collecting

ducts through the removal of water.• As filtrate travels through the collecting ducts

to the renal pelvis, it passes through areas of increasingly concentrated extracellular fluid.

• Water leaves the filtrate by osmosis and is carried off by the surrounding capillaries.


Filtration: Water, nutrients,and wastes are filtered from theglomerular capillaries into theBowman’s capsule of the nephron

Tubular reabsorption: In theproximal tubule, most water and nutrientsare reabsorbed into the blood

Tubular secretion:In the distal tubule,additional wastes areactively secreted into thetubule from the blood

Concentration: Inthe collecting duct,additional water mayleave, creating urinethat is more concentratedthan the blood

34-35.8 How Does The Human Urinary System Work? Urine formation in the nephron and

collecting duct

Fig. 34-35-19


34-35.8 How Does The Human Urinary System Work? Negative feedback regulates the water content of

the blood.• The amount of water reabsorbed into the blood is

controlled by negative feedback.• Antidiuretic hormone (ADH) regulates the amount of

water reabsorbed by the collecting ducts.• It does this by increasing the permeability of the distal

tubule and the collecting ducts to water.• The release of ADH from the pituitary is regulated by

receptor cells in the brain that monitor blood concentration.


34-35.8 How Does The Human Urinary System Work? Dehydration

stimulates ADH release and water retention.

Fig. 34-35-20

Receptors in the brain detectthe low water content of theblood and signal the pituitarygland

ADH increases thepermeability of the distal tubuleand the collecting duct,allowing more water to bereabsorbed into the blood

Water is retained in the bodyand concentrated urine isproduced

The pituitary glandreleases ADH into thebloodstream

Heat causes waterloss and dehydration


34-35.8 How Does The Human Urinary System Work?

PLAYPLAY Animation—Urine Formation

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