Essential Knowledge: 2.A.3 Organisms must exchange matter with the environment to grow, reproduce, and maintain organization2.D.2 Homeostatic mechanisms reflect both common ancestry and divergence due to adaptation in different environments.4.A.4 Organisms exhibit complex Properties due to interactions between constituent parts4.B.2 Cooperative interactions within organisms promote efficiency in the use of energy and matter

What are the main feeding mechanisms of Animals? How do they ingest food?◦ Suspension feeders – aquatic animals that sift

small food particles from water◦ Substrate feeders – animals that live in or on their

food source◦ Fluid feeders – animals that suck nutrient-rich

food from host◦ Bulk feeders – animals that eat relatively large

pieces of food

Obtaining Nutrients

What are the two modes of digestion?◦ Intracellular – hydrolysis of food inside vacuoles;

vacuoles fuse with lysosomes where food can be broken down without damaging the cell.

◦ Extracellular – breakdown of food in compartments that are continuous with the outside of the animal’s body Gastrovascular cavity – one opening; food enters

through the mouth and waste exit through the mouth Complete digestive system / alimentary canal – two

openings; food enters through the mouth and waste exits through the anus

Obtaining Nutrients

Esophagus

Mouth

Pharynx

Crop Gizzard

Typhlosole

Intestine

Lumen of intestine

Anus

(b) Grasshopper

Foregut

(c) Bird

(a) Earthworm

Midgut Hindgut

Esophagus RectumAnus

Mouth

Crop

Gastric cecae

EsophagusMouth

CropAnus

StomachGizzard

Intestine

GastrovascularcavityFood

Epidermis

Mouth

Tentacles

Gastrodermis

Cecum

Anus Anus

Ascendingportion oflarge intestine

Gall-bladder

Smallintestine

Largeintestine

Smallintestine

Rectum

Pancreas

Liver

Salivary glands

TongueOral cavityPharynxEsophagus

Sphincter

Stomach

Sphincter

Duodenum ofsmall intestine

Appendix

LiverPancreas

Smallintestine

Largeintestine

Rectum

StomachGall-bladder

A schematic diagram of thehuman digestive system

Esophagus

Salivaryglands

Mouth

Obtaining Nutrients How do humans get nutrients from food to

our cells?◦ Ingest food and begin to digest food in the mouth.

Mostly mechanical breakdown; some enzymatic breakdown of starch.

◦ Food/bolus passes from the mouth through the pharnx and esophagous to the stomach

What is the structure called that keeps food from passing into the trachea◦ Epiglottis closes over the glottis (the opening to

the trachea)

What do we call the rhythmic contractions of the esophagus that moves the bolus to the stomach?◦ perstalsis

Obtaining Nutrients

LarynxTrachea

Epiglottisup

PharynxTongue

Glottis

Esophagus

Esophagealsphinctercontracted

Food

Tostomach

Tolungs

EpiglottisdownEsophagealsphincterrelaxed

Glottis upand closed

Epiglottisup

Esophagealsphinctercontracted

Sphincterrelaxed

Relaxedmuscles Contracted

musclesRelaxedmuscles

Stomach

Glottisdownand open

What do you call the muscles that regulate entrance and exit of the stomach?◦ Sphincter muscles

What are the primary functions of the stomach?◦ Continued Digestion – chemical and mechanical◦ Storage of food

Upon entry into the stomach ingested food is mixed with gastric juice. What is this mixture called?◦ chyme

Obtaining Nutrients

What unique structures found within in the stomach allow it to do its job?◦ Highly folded interior surface of stomach – rugae◦ Gastric pits in the surface lead to gastric glands◦ Gastric glands have 3 types of specialized cells

Mucus cells – secrete mucus to protect lining of stomach

Parietal cells – secrete hydrochloric acid (HCl) Chief cells – secrete pepsinogen which becomes

pepsin in the presence of HCl – used to break down proteins

Obtaining Nutrients

Fig. 41-12

Interior surfaceof stomach

Esophagus

Chief cells

Small intestine

Epithelium

Stomach

Sphincter

Parietal cell

Pepsinogen and HClare secreted.

HCl convertspepsinogen to pepsin.

Pepsin activatesmore pepsinogen.

Chief cell

Folds ofepithelialtissue

Pepsin

Sphincter

Pepsinogen

HCl

H+

Cl–

Parietal cells

Mucus cells

Gastric gland

1

2

2

3

3

1

5 µm

Obtaining Nutrients Where does most of the enzymatic break down

of macromolecules from food occur?◦ Small intestine

Where does most of the absorption of nutrients take place?◦ Small intestine

How is the structure of the small intestine specialized for absorption?◦ Huge surface area created by finger-like projections

called villi◦ Each epithelial cell of villi have microvilli that are

exposed to the interior of the intestine

Muscle layers

Microvilli (brushborder) at apical(lumenal) surface

Vein carrying bloodto hepatic portal vein

Villi

Intestinal wall

KeyNutrientabsorption

Largecircularfolds

Bloodcapillaries

Epithelialcells

VilliLymphvessel

Basal surface

LactealEpithelial cells

Lumen

Obtaining Nutrients How are sugars such as glucose and fructose

absorbed?◦ The simple sugar fructose moves via facilitated

diffusion down their concentration gradient from the lumen of the small intestine into epithelial cells.

◦ Fructose continues to move from high to low concentration until they enter microscopic blood vessels in the villi

◦ Glucose and other nutrients are pumped against concentration gradients by the epithelial cells – to allow for maximum uptake of nutrients into blood vessels

What is the energy content of food measured in?◦ Kilocalories = Calories on a food label

What do we call the number of Calories a resting animal requires to fuel processes essential to life?◦ Basal Metabolic Rate (BMR) – the amount of energy we

“burn” lying motionless◦ 1,300 to 1,500 for females◦ 1,600 to 1,800 for males

What happens when we take in too many Calories?◦ Excess energy stored as glycogen or fat

Obtaining Nutrients

What are two roles of the large intestine?◦ Absorption of water by osmosis◦ Elimination of digestive waste – feces

How do the bacteria that reside in our large intestine help us?◦ They produce vitamins, such as biotin, vit K and

several B vitamins, including folic acid. What is the terminal portion of the large

intestine called?◦ rectum

Eliminating Wastes

What are the main processing centers for liquid waste?◦ Kidneys

Eliminating Wastes

Posteriorvena cavaRenal arteryand vein

Urinarybladder

Ureter

Aorta

Urethra(a) Excretory organs and

major associated blood

vessels

(b) Kidney structure

Section of kidneyfrom a rat

4 mm

Kidney

Ureter

RenalmedullaRenalcortex

Renalpelvis

How is the structure of a kidney specialized for excretion?◦ Each kidney contains about a million nephrons

Eliminating Wastes

Cortical

nephron

Juxtamedullary

nephron

Collecting

duct

(c) Nephron types

Torenalpelvi

s

Renalmedull

a

Renalcorte

x

10 µm

Afferent arteriole

from renal artery

Efferentarteriole

fromglomerulus

SEM

Branch ofrenal

vein

Descending

limb

Ascending

limb

Loop ofHenle

(d) Filtrate and blood flow

Vasarecta

Collectingduct

Distaltubule

Peritubular capillariesProximal tubule

Bowman’s capsule

Glomerulus

How do Nephrons elinimate waste?◦ Filtration: Fluid called filtrate is forced out of the

glomeruls (a ball of capillaries) and into the Bowman’s capsule (the cup-shaped swelling of a nephron)

◦ Reabsorption and Secretion: As the filtrate travels through the various sections of the neprhon - the prximal tubule, descending limb of the loop of Henle, the ascending limb of the loop of Henle, and the distal tublule - ions and nutrients are reabsorbed and waste is secreted

◦ Excretion: waste travels from nephron to collecting duct to the renal pelvis to the ureter to the urinary bladder and out the urethra

Eliminating Wastes

What happens at the Bowman’s Capsule?◦ Filtrate from the blood enters the nephron

What happens at the proximal tubule?◦ Drugs, poisons, and H+ are excreted◦ Nutrients, NaCl, Water, HCO3- are reabsorbed

What happens in the Loop of Henle?◦ Water and NaCl are reabsorbed

What happens in the distal tubule?◦ NaCl, Water, and HCO3- are reabsorbed◦ K+ and H+ are secreted

What happens in the collecting duct?◦ NaCl, Urea and water are reabsorbed

Eliminating Wastes

How does the solute concentration of the medulla and cortex maximize reabsorption?◦ The solute concentration is lowest in cortex of the

kidney and highest in the medulla

Eliminating Wastes

Key

Activetranspor

tPassivetranspor

t

INNERMEDULL

A

OUTERMEDULL

A

H2O

CORTEXFiltrat

e

Loop of

Henle

H2O K+HCO3–

H+NH

3

Proximal tubuleNaC

lNutrient

s

Distal tubule

K+ H+

HCO3–

H2O

H2O

NaCl

NaCl

NaCl

NaCl

Urea

Collecting

duct

NaCl