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

• mechanical and chemical = nutrient rich fluid known as acid chyme

• this material enters the small intestine through the normally closed pyloric sphincter

• stomach produces mucus lining from its epithelial cells for protection

• lumen of the stomach is eroded; replaced by mitosis every three days

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 by-product 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 solidIn 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

• 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

Circulation & Transport

• 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

• 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

Vertebrate Circulation

• Fishes: one atrium, one ventricle• Blood is pumped from the ventricle to the gills

(the gill circulation) where it picks upoxygen and disposes ofcarbon dioxide across thecapillary walls

• The gill capillaries convergeinto a vessel that carriesoxygenated blood to capillarybeds 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 forkedartery that splits theventricle’s output intothe pulmocutaneousand systemiccirculations

• Crocodiles, birds, and mammals: two atria and two ventricles– Left side receives and pumps

only oxygen-rich blood– Right side only

oxygen-poor blood

• 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

The Heart

• 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

Cardiac Cycle

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

• precapillary sphincters are located at the entrance to capillary beds

Circulation

• Due to the net effect of blood and osmotic pressures, the blood loses fluid as it travels through capillaries

Fig. 42.14*

• 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

The Lymphatic System

• Along lymph vessels are organs called lymph nodes– Filter the lymph and attack viruses and

bacteria– Filled with white blood cells specialized for

defense

• 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

Respiratory Organs

• 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

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 oxygen-

binding 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

Respiratory Pigments

• 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 surroundingsand hemoglobinreleases more oxygen

• For example, a drop in pHlowers the affinity of hemo-globin for O2, an effectcalled the Bohr shift

END