UNIT 9
Chapter 41: Animal Nutrition
Chapter 42: Circulation & Gas Exchange
Nutritional Requirements
• Energy
• underconsumption (undernourishment)
•high caloric intake = overconsumption
• Nutrition
• amino acids, fatty
acids, minerals, etc.
Nutritional Requirements
Essential: organism cannot manufacture it, must be ingested
preformed
Deficiency: lacking an essential nutrient
For example … there are 20
amino acids, but 8 of them must
be obtained preformed from an
animal’s diet. A diet lacking in
any of these amino acids leads
to a protein deficiency.
Nutritional Requirements
 Some fatty acids are also essential
 Deficiencies rare since diets usually don’t lack fat
 Vitamins and minerals required in relatively small amounts
 Low amounts can lead to severe problems
 Ex. vitamin C, vitamin K, vitamin D, Fe, Na, K
Food & Feeding
Most animals are categorized as herbivores, carnivores, or
omnivores based on their diets.
Animals acquire their food in a variety of ways:
suspension feeders – sift food particles
substrate feeders – live in/on food
fluid feeders – suck fluids rich in nutrients
bulk feeders – relatively large pieces of food
Food & Feeding
Food Processing
Food processing occurs in four main stages in animals:
1. Ingestion – eating
2. Digestion – chemical/enzymes
3. Absorption – uptake of macromolecule monomers
4. Elimination – undigested material passes
Food Processing
Digestion occurs in two ways:
1. Intracellular – gylcolysis, Krebs, etc.
2. Extracellular – chewing, muscle, etc.
 Complete digestive systems aka
alimentary canal
Begins with the mouth ends with
the anus
Digestion
In order to understand the principles of digestion, we will use the
mammalian system as a model. Passage through the alimentary
canal involves various glands that secrete digestive juices.
Some words to know related to digestion:
peristalsis – rhythmic muscular contractions, pushes food
along
sphincters – ringlike muscles, regulates flow of food
accessory glands – salivary glands, pancreas, liver, and
gallbladder
Digestion TRIVIA
So, how long does it take for food to pass through the entire
length of the human alimentary canal?
5-10 seconds from mouth to stomach (ingestion)
2-6 hours in the stomach (digestion)
5-6 hours in the small intestine (absorption)
12-24 hours through the large intestine, undigested
material, feces out through the anus (elimination)
Digestion - Ingestion
Food processing begins in the oral cavity (mouth), pharynx, and
esophagus.
1. Mastication (chewing) involves the teeth cutting,
smashing, and grinding food = increases surface
area of food
2. A nervous reflex triggers the production of saliva,
(mucin, antibacterial, buffers) salivary amylase
hydrolyzes starch
3. A ball of food called a bolus is pushed into the pharynx
by the tongue
Digestion - Ingestion
• epiglottis covers the opening to the
trachea
•ensures that the bolus will travel
down the esophagus
Digestion - Digestion
The stomach is located just below the diaphragm and produces
acidic gastric juices
high concentration of HCl = pH 2
disrupts extracellular matrix
kills MOST bacteria
• stomach also produces pepsinogen
• in high acidic environments is converted to pepsin
• enzyme hydrolyzes proteins
Digestion - Digestion
• stomach produces mucus lining from its epithelial cells for
protection
• lumen of the stomach is eroded; replaced by mitosis every
three days
• mechanical and chemical = nutrient
rich fluid known as acid chyme
• this material enters the small
intestine through the normally
closed pyloric sphincter
Digestion – Digestion
• first 25cm (6m total) of the small intestine is the duodenum
• acid chyme is mixed with secretions from the pancreas,
liver, and gall bladder
• pancreas produces
enzymes in an alkaline
solution which buffers
the acidity of the
chyme
Digestion – Digestion
• liver produces
bile (stored in the
gall bladder)
which emulsifies
fats
• also contains
pigments that
are the byproduct of red
blood cell
destruction
Digestion – Absorption
The small intestine has an approximate surface area of 300m2!
• surface area is due to villi and microvilli on the wall of the
lumen
Digestion – Absorption/Elimination
• large intestine (colon) is responsible for reclamation of water
• process makes the feces progressively more solid
In the colon there lives a rich community of bacteria including
Escherichia coli. In addition to waste gases (methane, H2S),
they also produce biotin, folic acid, vitamin K, and several B
vitamins to supplement our dietary intake.
Diversity in Digestion
Structural
adaptations of
the digestive
system are often
times reflective
of an animal’s
diet. Such
adaptations can
include those to
dentition and
alimentary canal
structure.
END
Circulation & Transport
• Transport of fluids throughout the body
connects internal environment of the body
cells to the organs that exchange gases,
absorb nutrients, and dispose of wastes
– Ex. mammalian lung: oxygen from inhaled air
diffuses across a thin epithelium and into the
blood, while carbon dioxide diffuses out
– fluid movement in the circulatory system,
powered by the heart, quickly carries the
oxygen-rich blood to all parts of the body
• Open circulatory system: found in
insects, other arthropods
• No distinction
between blood and
interstitial fluid
• Heart(s) pump
hemolymph into
sinuses
• Closed circulatory system: found in
earthworms, squid, octopuses, and
vertebrates
• Blood is confined to vessels
– Heart(s) pump
blood into large vessels
that branch into smaller
ones
– Diffusion occurs between
between the blood
and the fluid around cells
• System of humans and other vertebrates is
often called the cardiovascular system
• Heart consists of:
– One atrium or two atria = the chambers that
receive blood returning to the heart
– One or two ventricles = the chambers that pump
blood out of the heart
Vertebrate Circulation
• Arteries, veins, and capillaries are the
three main kinds of blood vessels
– Arteries carry blood away from the heart to
organs
– Arteries branch into arterioles, smaller vessels
that bring blood to capillaries
– Capillaries (very thin, porous walls) form
capillary beds, that infiltrate each tissue
– Capillaries converge into venules, and venules
converge into veins, which return blood to the
heart
• Fishes: one atrium, one ventricle
• Blood is pumped from the ventricle to the gills
(the gill circulation) where it picks up
oxygen and disposes of
carbon dioxide across the
capillary walls
• The gill capillaries converge
into a vessel that carries
oxygenated blood to capillary
beds at the other organs
(the systemic circulation)
and back to the heart
• Amphibians and most reptiles: two atria
and one ventricle
– The ventricle pumps
blood into a forked
artery that splits the
ventricle’s output into
the pulmocutaneous
and systemic
circulations
• Crocodiles, birds, and mammals: two atria
and two ventricles
– Left side  receives and pumps
only oxygen-rich blood
– Right side  only
oxygen-poor blood
The Heart
• Evolution of a powerful four-chambered
heart was an essential adaptation to
support endothermy and larger body size
– Endotherms use about ten times as much
energy as ectotherms of the same size
• Endotherm circulatory system needs to deliver more
fuel and O2 … and remove ten times as much
wastes and CO2
Cardiac Cycle
• Cardiac cycle is one complete sequence
of pumping, as the heart contracts, and
filling, as it relaxes and its chambers fill with
blood
– Contraction phase is called systole, and the
relaxation phase is called diastole
Fig. 42.7
• Valves in the heart prevent backflow and
keep blood moving in the correct direction
– Atrioventricular (AV) valve
– Semilunar valves
• Certain cells of vertebrate cardiac muscle
are self-excitable - they contract without any
signal from the nervous system
– Each cell has its own natural contraction rhythm
– Cells are synchronized by the sinoatrial (SA)
node, or pacemaker, which sets the rate and
timing at which all cardiac muscle cells contract
• Cardiac cycle is regulated by electrical
impulses that spread throughout the heart
– Cells are electrically coupled by intercalated
disks between adjacent cells
Fig. 42.8
Circulation
• precapillary
sphincters are
located at the
entrance to capillary
beds
• Due to the net effect of blood and osmotic
pressures, the blood loses fluid as it travels
through capillaries
Fig. 42.14*
The Lymphatic System
• Fluids and some blood proteins that leak
from the capillaries into the interstitial fluid
are returned to the blood via the lymphatic
system
– Fluid enters system by diffusing into tiny lymph
capillaries intermingled among blood capillaries
– Inside the lymphatic system, the fluid is called
lymph
– Lymphatic system drains into the circulatory
system near the junction of the vena cava
• Along lymph vessels are organs called
lymph nodes
– Filter the lymph and attack viruses and
bacteria
– Filled with white blood cells specialized for
defense
Respiratory Organs
• Gills are folds in tissue that are suspended in
water
– Total surface area of gills is often much
greater than that of the rest of the body
• Flow pattern of water
over a fish’s gills is
called
countercurrent flow
• Tiniest bronchioles dead-end as a cluster of
air sacs called alveoli
– Gas exchange occurs across the thin
epithelium of the lung’s millions of alveoli
• Mammals fill (ventilate) their lungs by
negative pressure breathing
• Like a suction pump, pulling air instead of
pushing it into the lungs
• Diaphragm is the muscle that makes this happen
• Volume of air an animal inhales and
exhales with each breath is called tidal
volume
• About 500 mL in resting humans
– Maximum tidal volume during forced breathing
= vital capacity
– Lungs hold more air than the vital capacity
(some air remains in the lungs) the residual
volume
Respiratory Pigments
Oxygen’s low solubility in water is a major
problem for animals.
• Respiratory pigments have evolved in
various animals
– Ex. Hemocyanin: has copper as its oxygenbinding component
– Pigment of almost all vertebrates is the protein
hemoglobin
• Hemoglobin consists of four subunits, each with a
cofactor called a heme group that has an iron atom
at its center
• Oxygen binding and release is shown in the
dissociation curve for hemoglobin
• Where the dissociation curve has a steep slope,
even a slight change in PO2 causes hemoglobin
to load or unload a substantial amount of O2
• Steep part
corresponds to the range
of partial pressures
found in body tissues
• As with all proteins, hemoglobin’s
conformation is sensitive to a variety of
factors
• CO2 forms carbonic acid,
an active tissue will lower
the pH of its surroundings
and hemoglobin
releases more oxygen
• For example, a drop in pH
lowers the affinity of hemoglobin for O2, an effect
called the Bohr shift
END