what are the main feeding mechanisms of animals? how do they ingest food? ◦ suspension feeders –...
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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
Esophagus
Mouth
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 cavity
PharynxEsophagus
Sphincter
Stomach
Sphincter
Duodenum ofsmall intestine
Appendix
Liver
Pancreas
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
Epiglottisdown
Esophagealsphincterrelaxed
Glottis upand closed
Epiglottisup
Esophagealsphinctercontracted
Sphincterrelaxed
Relaxedmuscles
ContractedmusclesRelaxed
muscles
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 µ
m
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
Key
Nutrientabsorption
Largecircularfolds
Bloodcapillaries
Epithelialcells
Villi
Lymphvessel
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 capillaries
Proximal tubuleBowman’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