unit 9 chapter 41: animal nutrition chapter 42: circulation & gas exchange
TRANSCRIPT
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.
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• 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