Cells are organized in the following ways:

• Tissues (groups of similar cells performing a common function. Animal tissues are organized into four general categories…

• Epithelial (tissue such as outer skin layers and internal protective coverings)

• Connective (tissue such as bone, cartilage, and blood)

• Nervous (tissue of the nervous system)

• Muscle (tissue of the muscular system)

• Organs (groups of tissues functioning together)

• Organ Systems (groups of organs functioning together

• Organism (the whole banana!)

The function of many animal systems is to contribute toward homeostasis, or maintenance of stable, internal conditions within narrow limits.

In many cases, homeostasis is maintained by negative feedback. A sensing mechanism (a receptor) detects a change in conditions beyond specific range. A control center, or integrator (often the brain), evaluates the change and activates a second mechanism (an effector) to correct the condition.

In “negative” feedback, the original condition is negated, so that the conditions are returned to normal. (see below)

Compare this with positive feedback, in which an action intensifies a condition so that it is driven further beyond normal limits. (Lactation is stimulated in response to increased nursing of an infant.

Animal cells require O2 for aerobic respiration. Cells must have some mechanism for providing gas exchange , delivering O2 and removing waste CO2.

The process, on a cellular level, produces ATP within the mitochondria of cells (review respiration PPT). The following gas exchange mechanisms are found in animals:

• direct with the environment: such as platyhelminthes, where every cell is exposed to the outside environment, and gases may diffuse readily.

• gills which are evaginated (outgrowths) from the body, that create a large surface area over which gas exchange occurs. Circulatory system delivers O2 and carries away CO2 from gills.

Gills can be internal, covered by operculum (fish), and external and unprotected)

•tracheae found in insects which have chitin-lined tubes that permeate their bodies. (insects) O2 enters, and CO2 exits through openings called spiracles

• lungs which are invaginated (cavities within the body). Book lungs are found within many spiders, are stacks of flattened membranes enclosed

•Nose, pharynx, larynx: air enters the nose and passes through the nasal cavity, pharynx, and larynx. The larynx (voice box) contains the vocal cords.

• Trachea: air enters a cartilage-lined tube called the trachea. A flap called the epiglottis covers the trachea when food is being swallowed. It prevents the entrance of solid and liquid materials from getting into the lungs.

• Bronchi, bronchioles: the trachea branches into two bronchi, which enter the lungs and then branch repeatedly, forming narrower tubes called bronchioles.

• Alveolus: each bronchiole branch ends in a small sac called an alveolus (plural, alveoli). Each alveolus is densely surrounded by blood-carrying capillaries.

• Diffusion between alveolar chambers and blood: gas exchange occurs by diffusion across the moist, sac membranes of the alveoli. Oxygen diffuses into the red blood cells in the capillary beds surrounding the alveoli, and CO2 diffuses out in the opposite direction.

• Bulk flow of O2: The circulatory system transports O2 throughout the

body within red blood cells, which contain hemoglobin, iron-containing proteins to which O2 bonds.

• Diffusion between blood and cells: blood capillaries permeate the body. Oxygen diffuses out of the red blood cells, across blood capillary walls, into interstitial fluids (the fluids surrounding the cells), and across cell

membranes. Carbon dioxide diffuses in the opposite direction.

• Bulk flow of CO2: Most CO2 is transported as dissolved bicarbonate ions (HCO3

-) in the plasma, the liquid portion of the blood. The formation of HCO3

-, however, occurs in the red blood cells, where the formation of carbonic acid (H2CO3) is catalyzed by the enzyme carbonic anhydrase, as follows:

CO2 + H2O H2CO3 H+ + HCO3

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Following their formation in the red blood cells, HCO3- ions

diffuse back into the plasma. Some CO2, however, does not become HCO3

-; instead, it mixes directly with the plasma (as CO2 gas) or binds with the amino groups of the hemoglobin molecules inside red blood cells.

• Mechanics of respiration: air is moved into and out of the lungs by changing their volume. The volume of the lungs is increased by the contraction of the diaphragm and the intercostal muscles between the ribs. When the lung volume increases, the air pressure within the lungs decreases. This causes a pressure difference between the air in the lungs and the air outside the body. As a result, air rushes into the lungs by bulk flow. When the diaphragm and intercostal muscles relax, the volume of the lungs decreases, raising the pressure on the air, causing the air to rush out.

• Control of respiration: chemoreceptors in the carotid arteries (supply blood to the brain) monitor the pH of the blood. When a body is active, CO2 production increases. When CO2 enters the plasma and is converted to HCO3

-, and H+, the blood pH drops. In response, the chemoreceptors send nerve impulses to the diaphragm and intercostal muscles to increase respiratory rate. This results in a faster turnover in gas exchange, which returns blood pH to normal. This is a homeostatic negative feedback loop.

Large organisms require a transport system to distribute nutrients and oxygen and to remove wastes from cells. Two kinds of circulatory systems accomplish this:

• Open Circulatory System: pump blood into an internal cavity called a hemocoel, or sinuses, which bathe tissues with an oxygen-and nutrient-carrying fluid called hemolymph. The hemolymph returns to the pumping mechanism of the system, a heart, through holes called ostia. Open circulatory systems occur in insects and most mollusks.

• Closed Circulatory Systems: the nutrient, oxygen, and waste-carrying fluid, known as blood, is confined to vessels. Closed circulatory systems are found among members of the phylum annelida, certain mollusks, (octopuses and squids) and vertebrates.

In the closed circulatory system of vertebrates, vessels moving away from the heart are called arteries. Arteries branch into smaller arterioles, and then branch further into the smallest vessels, capillaries. Gas and nutrient exchange occurs by diffusion across capillary walls into interstitial fluids and into surrounding cells. Wastes and excess interstitial fluids move in the opposite direction as they diffuse into capillaries. The blood, now deoxygenated, remains in the capillaries and returns to the heart through venules, which merge to form veins. The heart then pumps the deoxygenated blood to the respiratory organ (gills or lungs), where arteries again branch into a capillary bed for gas exchange. The oxygenated blood then returns to the heart through veins. From here, the oxygenated blood is pumped once again, through the body.

• KNOW the path of blood through the body, heart, and lungs!!!

• KNOW in which vessels it is deoxygenated and in which vessels it is oxygenated.

The pathway of blood between the right side of the heart, to the lungs, and back to the left side of the heart is called the pulmonary circuit. The circulation pathway throughout the body is the systemic circuit.

• The cardiac or heart cycle: refers to the rhythmic contraction and relaxation of heart muscles. It is regulated by specialized tissues in the heart called autorhythmic cells, which are self-excitable and able to initiate contractions without external stimulation by nerve cells. The cycle occurs as follows: The SA (sinoatrial) node, or pacemaker: found in

upper wall of right atrium, spontaneously initiates the cycle by simultaneously contracting both atria and also sending a delayed impulse that stimulates the AV (atrioventricular) node. The AV node found in the lower wall of the right atrium sends an impulse through the bundle of His, nodal tissue that passes down between both ventricles and then branches into the ventricles through the Purkinje fibers. This impulse results in the contraction of the ventricles. When the ventricles contract (the systole phase), blood is forced through the pulmonary arteries and aorta. Also the AV valves are closed. When the ventricles relax (the diastole phase), backflow into the ventricles causes the semilunar valves to close. The closing of the AV valves, followed by the closing of the semilunar valves, produces the characteristic “lub-dub” sound of the heart.

Wastes and excess interstitial fluids enter the circulatory system when they diffuse into capillaries. However, not all of the interstitial fluids enter the capillaries. Instead, some are returned to the circulatory system by way of the lymphatic system, which is a second network of capillaries and veins.

The fluid in these lymphatic veins, called lymph, moves slowly through lymphatic vessels by the contractions of adjacent muscles. Valves in the lymphatic veins prevent backflow. Lymph returns to the blood circulatory system through two ducts located in the shoulder region. In addition to returning fluids to the circulatory system, the lymphatic system functions as a filter. Lymph nodes, enlarged bodies throughout the lymphatic system, act as cleaning filters and as immune response centers that defend against infection. This is why they tend to get “swollen” when you are ill.

Blood contains each of the following:

• Red blood cells (erythrocytes) transport oxygen and catalyze the conversion of CO2 and H2O to H2CO3. Mature red blood cells lack a nucleus, thereby maximizing hemoglobin content and thus their ability to transport O2.

• White blood cells (leukocytes) consist of five major groups of disease-fighting cells that defend the body against infection.• Platelets are cell fragments that are involved in blood clotting. Platelets release factors that are involved in the conversion of the major clotting agent, fibrinogen, into its active form, fibrin. Threads of fibrin protein form a network that stops blood flow.

• Plasma is the liquid portion of the blood that contains various dissolved substances.

WBCs: Monocytes; Neutrophiles, Eosinophiles, Basophiles, and Macrophages. (each has its own function within the blood)

In general, the excretory system helps maintain homeostasis in organisms by regulating water balance and by removing harmful substances.

Osmoregulation: is the absorption and excretion of water and dissolved substances (solutes) so that proper water balance is maintained between the organism and its surroundings. Two examples:•Marine Fish: are hypoosmotic with their environment. (less salty than the surrounding water). Water is constantly lost through osmosis. To maintain proper internal environment, marine fish constantly drink, rarely urinate, and secrete accumulated salts through their gills.

• Fresh Water Fish: are hyperosmotic, or saltier than the surrounding water. Thus, water constantly diffuses into the fish. In response, fresh water fish rarely drink, constantly urinate, and absorb salts through their gills.

Many mechanisms have evolved for osmoregulation in animals, and for the regulation of toxic substances, such as the by-products of cellular metabolism (nitrogen products of protein breakdown). Examples:Contractile Vacuole: found in the cytoplasm of Protists like paramecia and amoeba. They accumulate water within the organism, merge with the plasma membrane, and release water.

Flame Cells: found within Platyhelminthes, such as planaria. Ciliated cells filter body fluids moving through a tube system. Water is excreted from pores that exit the body.

Nephridia (or metanephridia) occur in pairs within each segment of most annelids. Fluids pass through a series of collecting tubules, where needed substances are reabsorbed. Wastes are excreted through excretory pores.

• Malpighian tubules: occur in many arthropods, such as insects. Tubes attached to the midsection of the digestive tract collect body fluids from the hemolymph that bathes the cells. Waste materials, and needed materials are deposited into the midgut. Needed materials continue through the digestive system, while wastes continue and are excreted through the anus.Kidneys: occur in

vertebrates, and consist of about a million individual filtering tubes called nephrons. Two kidneys produce waste fluids, or urine, which pass through ureters to the bladder for temporary storage. From the bladder, the urine is excreted through the urethra.

The Nephron

Let’s get a closer look…

1. Bowman’s capsule: the nephron tube begins with a bulb-shaped body at one end. A branch of the renal artery (afferent arteriole) enters into the Bowman’s capsule, branches to form a dense ball of capillaries called the glomerulus, and then exits the capsule (efferent arteriole)

2. Convoluted tubule: long twisting tub beginning with the proximal convoluted tubule (proximal to the Bowman’s capsule) and ends with the distal convoluted tubule (distant to Bowman’s capsule), where it joins the collecting duct.

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3. Loop of Henle: occurs in between the proximal and distal convoluted tubule.

4. Collecting duct: The distal convoluted tubule empties into the collection duct, which empties into the renal pelvis, draining into the ureter.

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• Filtration: when blood enters the glomerulus, pressure forces water and solutes through the capillary walls into the Bowman’s capsule. Solutes include glucose, salts, vitamins, nitrogen wastes, and any other substances small enough to pass through the capillary walls. Red blood cells, and proteins remain in the capillaries. The other materials diffuse into the Bowman’s capsule, and then flow into the convoluted tubule.

• Secretion: As a filtrete passes through the proximal tubule and, later, through the distal tubule, additional material from the interstitial fluids joins the filtrete. This material is selectively secreted into the convoluted tubule by both passive and active transport.

• Reabsorption: when filtrete moves down the loop of Henle, it becomes more concentrated due to passive flow of H2O out of the tube. As the filtrete moves up the loop of Henle, it becomes more dilute due to passive and active transport of salts out of the tubule. These salts move into the interstitial fluids, and as the tubule passes towards the renal pelvis, water passively moves out of the collecting duct and into the interstitial fluids. (osmosis, homeostasis). When the filtrete drains into the renal pelvis, it is concentrated urine.

1. Antidiuretic hormone (ADH) increases the reabsorption of water by the body and increases the concentration of salts in the urine. It does this by increasing the permeability of the collecting duct to water. As a result, more water diffuses out of the collecting duct as the filtrete descends into the renal pelvis.

2. Aldosterone increases both the reabsorption of water and the reabsorption of Na+. It does this by increasing the permeability of the distal convoluted tubule and collecting duct to Na+. As a result, more Na+ diffuses out of this tubule and duct. Since the Na+ increases the salt concentration outside the tubule, water passively follows.

Nitrogen forms a major waste product in animals. When amino acids and nucleic acids are broken down, they release toxic ammonia (NH3). To rid the body of this toxin, several mechanisms have evolved, each appropriate to the habitat or survival of the animal.

• Aquatic animals excrete NH3 directly into the surrounding water

• Mammals convert NH3 to urea in their livers. Urea is significantly less toxic than NH3, and thus requires less water to excrete in the urine

• Birds, insects, and many reptiles convert urea to uric acid, which is a solid. This allows considerable water conservation by permitting the excretion of nitrogen waste as a solid.

Simply put, is the breakdown of food into smaller molecules. It can occur in cells (lysosomes containing digestive enzymes merge with food vacuoles, and it can be extracellular as well. Food ingested is too large to be engulfed by individual cells, thus it is first digested in the gastrovascular cavity, and then absorbed by individual cells.

In humans and other mammals, digestion follows a particular series of events. Molecules are digested by specific enzymes. It begins in the MOUTH…

During digestion there are four molecules are commonly encountered:

• Starches: broken down into glucose molecules

• Proteins: broken down into amino acids

• Fats (lipids): broken down into fatty acids, and glycerol

• Nucleic acids: broken down into nucleotides

• Mouth (Salivary Amylase): secreted into the mouth by the salivary glands, begins the breakdown of starches into maltose (a disaccharide). Chewing reduces the size of food (mechanical digestion), thereby increasing the surface area upon which amylase and subsequent enzymes can operate. Food is shaped into a ball (bolus) and then swallowed.

• Pharynx: when food is swallowed and passed into the throat, or pharynx, a flap of tissue, called the epiglottis, blocks the trachea so that solid and liquid material enter only the esophagus (tube to stomach).

• Esophagus: food moves through the esophagus by muscular contractions called peristalsis.

• Stomach: secretes gastric juice, a mixture of digestive enzymes (pepsin) and hydrochloric acid.

•Storage: because of its accordion-like folds, the wall of the stomach can expand to store two to four liters of material.

• Mixing: mixes the food with water and gastric juice to produce a creamy medium called chyme (KIME)

• Physical Breakdown: muscles churn the contents breaking the food into smaller particles (mechanical digestion).

• Chemical Breakdown: Proteins are chemically broken down with pepsin, and HCL. The stomach is protected by a layer of mucous. Failure of this lining can lead to peptic ulcers.

• Controlled Release:

The stomach serves a variety of functions:

Movement of chyme into the small intestine is regulated by a valve called the pyloric sphincter.

• Small Intestine: the first twenty-five cm of the small intestine is called the duodenum continues digestion of starches and proteins. Enzymes originate from the following sources:

• small intestine: the wall of the small intestine is the source of various enzymes, including proteolytic enzymes (digesting proteins), maltase and lactase (digesting carbohydrates), and phosphateses (digestion of nucleotides).

• pancreas: produces trypsin and chymotrypsin, lipase (digestion of fats), and pancreatic amylase (starch digestion) These and other enzymes serve to neutralize the HCL in the chyme entering the duodenum. • Liver: produces bile which functions to emulsify fats. This is the physical breaking up of fat into smaller fat droplets, increasing the surface area upon which fat-digesting enzymes (lipase) can operate. Since bile does not chemically change anything, it is not an enzyme. While bile is produced in the liver, in most organisms, it is stored in the gall bladder.

• The remainder of the small intestine (jejunum, and ileum) which is nearly six meters in length, absorbs the breakdown products of food. Villi and microvilli, fingerlike projections of the intestinal wall, increase the surface area greatly, facilitating a greater reabsorptive potential. Amino acids and sugars are absorbed into the blood capillaries, while most of the fatty acids and glycerol are absorbed into the lymphatic system.

•Large intestine: the main function of the large intestine (colon) is the reabsorption of water to form solid waste, or feces. Feces are stored at the end of the large intestine, in the rectum, and are excreted through the anus.

Various mutualistic bacteria live within the large intestine, including some that produce vitamin K, which is absorbed through the intestinal wall. At the beginning of the largeThe colon has five parts you should be aware of:

• Cecum: short dead-end pouch from which the vestigial appendix hangs.

• Ascending colon: moves up the right side of the body

• Transverse colon: moves across the abdomen.

• Descending colon: moves down the left side of the abdomen

• Sigmoid colon: last section shaped like an “S” empties into the rectum.

Endocrine and digestion:

• Gastrin: produced by stomach lining when nervous system senses the availability of food (sight or smell) stimulates production of gastric juice.

• Secretin: produced by duodenum, stimulates pancreas to produce bicarbonate, neutralizing acid in chyme.

There are two types of skeletal systems. An exoskeleton can be found on many invertebrate arthropods, such as insects and crustaceans. It is a chitinous skeleton surrounding the exterior of the organism. It serves to anchor internal organs, and provide support and protection for body systems.

The other type of skeleton is the one we are most familiar with, because we have one ourselves! It is an endoskeleton. This skeleton serves to protect and support us from within our bodies. All vertebrates (except some very primitive fishes) have a complex bony skeleton.

• Provides a framework and support structure for the tissues of your body to attach to• Protects your internal organs, including your heart, lungs, and brain• Produces red blood cells, and some white blood cells

• A storehouse for minerals such as calcium and phosphorous

• Along with muscles, acts to help the body with locomotion and other movement

The adult human skeleton has 206 bones, give or take. All bony tissue is not the same, however.

• Compact bone: the outer most dense bony material

• Spongy bone: inner porous less dense bone

• Marrow: soft material in the inner cavity of bone

They are long tubular systems which run the length of compact bone tissue, and contain nerves and tiny blood vesselsBone marrow is a special, spongy, fatty tissue that houses

stem cells, located inside a few large bones. These stem cells transform themselves into white and red blood cells and platelets, essential for immunity and circulation. Anemia, leukemia, and other lymphoma cancers can compromise the resilience of bone marrow.

Our skull, sternum, ribs, pelvis, and femur bones all contain bone marrow, but other smaller bones do not. Inside this special tissue, immature stems cells reside, along with extra iron. While they are undifferentiated, the stem cells wait until unhealthy, weakened, or damaged cells need to be replaced. A stem cell can turn itself into a platelet, a white blood cell like a T-cell, or a red blood cell. This is the only way such cells get replaced to keep our body healthy.

Found inside compact bone…