General Zoology
Gas Exchange in Animals / Respiration Overview
Oxygen is essential for physiological processes
Animals obtain oxygen through various methods
Gas exchange occurs through the circulatory and respiratory systems
Focus of the lecture is on the respiratory system
Learning Objectives
Identify different ways animals obtain oxygen
Identify organs involved in respiration
Differentiate types of respiration in organ
General Discussion
Respiration involves the exchange of gases during breathing
Two types of respiration: cellular respiration and external respiration
Respiration process depends on the environment
Land organisms have easier access to oxygen compared to aquatic organisms
Aquatic organisms have developed efficient ways to extract oxygen from water, but it requires more energy
The Respiratory Organs of Animals: Cutaneous Respiration
Single-celled organisms and lower forms of animals obtain oxygen through direct diffusion
Cutaneous respiration uses the skin for respiration
Thin skins in invertebrates allow for direct diffusion of oxygen
Larger organisms with cutaneous respiration increase body surface area for more efficient respiration
The Tracheal Systems
Insects and arthropods use tracheal systems for respiration
Tracheal system consists of tubes (tracheae) that reach all parts of the body
Tracheae have fluid-filled tracheoles and air enters through spiracles
Respiratory mechanism in insects and arthropods is independent of circulatory system
Oxygen and carbon dioxide can freely diffuse through tracheal systems
The Gills
Gills are the primary respiratory mechanism for higher forms of aquatic organisms
External gills are extensions of the body and obtain oxygen through diffusion
Internal gills are filamentous structures heavily supplied by blood vessels
Countercurrent flow enhances oxygen intake in internal gills
Fishes have a dual pump system for water flow in gills
The Lungs
Lungs are the main respiratory apparatus in terrestrial environments
Lungs are more efficient than gills in land organisms
Some invertebrates also possess lungs, but they are less efficient
Lungfish have gas bladders that function like lungs during dry seasons
Amphibians have varied lung structures and undergo buccal pumping for respiration
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Avian lungs have an extensive system of air sacs
25% of air passes through lung parabronchi for gas exchange
75% of air bypasses lungs and goes to air sacs
Fresh air from air sacs passes through lungs and parabronchi during release of gases
Mammalian lungs have alveoli for gas exchange
Exchange of gases only occurs within the air sacs, creating a "dead space"
Mammals exhibit bidirectional respiration
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Mammalian lungs are covered by visceral pleura and parietal pleura
Pleural cavity maintains negative intrapleural pressure for lung expansion
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Ventilation of the lungs involves inspiration and expiration
During inspiration, ribs and diaphragm expand lungs, decreasing pressure and allowing air to rush in
During expiration, ribs and diaphragm return to normal position, increasing pressure and forcing air out
The Transportation of Gases:
Invertebrates with open circulation freely transport gases with body fluids
Low metabolic rate organisms may have inadequate oxygen, so respiratory pigments like hemoglobin transport oxygen
Hemoglobin has a high affinity for oxygen and carries it from alveoli to blood cells
Oxygen is released from hemoglobin when it reaches tissues
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Exchange of gases between the bloodstream and tissue cells
This is one of the functions of the respiratory system
Exchange of gases between alveoli and the bloodstream
Alveoli are small air sacs in the lungs where gas exchange occurs
Breathing between the atmosphere and the alveoli
Breathing is the process of inhaling and exhaling air
Which of the following organs functions as an air conditioner?
Larynx
Nasal chambers
Pharynx
All of the above
The normal breathing process is controlled by ____________.
Lungs
Dorsal respiratory group
Ventral respiratory group
Both (b) and (c)
In Aves, the exchange of gases occurs within the __________.
Lungs
Air sacs and lungs
Air sacs
None of the above
Which of the following statements is true about the entry of air into the lungs?
Air enters the body and travels to the lungs through the mouth and the nose
Air enters the body and travels to the lungs through the oesophagus and gullet
Air enters the body and travels to the lungs through the windpipe and the pores
Air enters the body and travels to the lungs through the nose and the nervous system
The windpipe is also called the ________.
Larynx
Trachea
Lungs
Oesophagus
In Earthworms, the process of respiration is through ________.
Skin
Lungs
Head
Pores on its anterior end
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Chapter 11. The Internal Transport Mechanism in Animals / Circulatory System Overview
Animals require nutrients for them to survive
Nutrients are obtained from the food that the organism eats
The circulatory system is essential for transferring nutrients and oxygen throughout the body
The circulatory system supplies blood to the entire body and ensures the normal functioning of organs
The circulatory system is responsible for protection against microorganisms
Learning objectives:
Identify the flow of blood throughout the body
Differentiate the circulatory system of invertebrates and vertebrates
Classify the different blood cells involved in the system
Understand the mechanism of the lymphatic system
Understand the types of circulations
General Discussion
Organisms require nutrients and oxygen for growth and development
Unicellular organisms can obtain nutrients and oxygen through their cellular membrane
Larger, multicellular organisms rely on the circulatory system to transport nutrients and oxygen
The circulatory system also transports hormones, waste materials, and other bodily fluids
The circulatory system accelerates the transportation of materials, especially in the presence of diseases
The Internal Body Fluids
Animal body fluids are divided into intracellular and extracellular fluids
Intracellular fluids are located inside the cell, while extracellular fluids are located outside the cells
Closed circulatory systems have extracellular fluids classified into blood plasma and interstitial fluids
The interstitial fluid surrounds the cells and is formed from the plasma
Body fluids are composed mostly of water, with different organic and inorganic substances
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The Blood
Blood is not present in all animal species
Invertebrates may have an open circulatory system with a mixture called hemolymph
Organisms with a closed circulatory system have blood enclosed within vessels
Blood is composed of plasma and cellular components
Plasma
Composed of 90% water and 10% dissolved solids and gases
Plasma proteins include albumin, globulins, and fibrinogen
Albumin regulates osmotic equilibrium, globulins are responsible for immune responses, and fibrinogen aids in blood coagulation
Cellular Components
Divided into erythrocytes (red blood cells), leukocytes (white blood cells), and thrombocytes (platelets)
Erythrocytes transport gases, leukocytes are responsible for immune response, and thrombocytes aid in blood coagulation
The Red Blood Cells
Red blood cells are essential for the transport of oxygen
Appearance varies depending on the organism
Bird and mammalian red blood cells are anucleated and biconcave in shape
Other vertebrate species have red blood cells with a nucleus and ellipsoid shape
Macrophages engulf and absorb non-functional red blood cells
The White Blood Cells
White blood cells are responsible for the immune response
They can be classified as granulocytes (neutrophil, basophil, eosinophil) or agranulocytes (monocyte, lymphocyte)
Neutrophils are responsible for phagocytosis, basophils release histamines and promote inflammation
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Eosinophil, Monocytes, and Lymphocytes are types of white blood cells
Eosinophil has a bilobed nucleus and is responsible for inflammatory response of allergies and parasitic invasion
Monocytes have a large kidney-shaped nucleus and are responsible for phagocytosis of microorganisms; can transform into macrophages
Lymphocytes have a circular nucleus and are responsible for producing antibodies and other chemicals for immune response
Fig. 1 shows different types of white blood cells
Hemostasis:
Blood is responsible for transporting nutrients and oxygen throughout the body
Contraction of smooth muscles in blood vessels stops bleeding in closed circulatory systems
Hemolymph in open circulatory systems contains clotting factors and amoeboid cells to prevent fluid loss
Fibrinogen and thrombin play a role in preventing blood loss in vertebrates
Prothrombin needs to be activated for clotting process to initiate
Platelets adhere to damaged vessel surfaces and release thromboplastins to activate prothrombin and start clotting process
Fig. 2 shows blood clotting process
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Circulation Process:
Circulation is the process of transporting nutrients and gases in the body
Smaller organisms use simple diffusion for circulation
Larger organisms need an extensive network of blood vessels for circulation
Circulation can be open or closed
Open circulation has no vessels, uses hemocoel for blood circulation
Hemolymph volume is larger in open circulation compared to mammalian blood volume
Arthropods have hearts in the hemocoel and auxiliary hearts to boost blood movement
Closed circulation has an extensive network of blood vessels
Blood is separated from bodily fluids and flows through heart, artery, arteriole, capillary, venule, and vein
Capillaries have thin walls for free diffusion of blood
Fig. 3 shows body plan of animals with closed and open circulation
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Vertebrate Circulatory System:
Vertebrates have chambered hearts
Fish have two chambers (atrium and ventricle) and a single circuit for circulation
Lungs evolved, leading to dual circuit circulation in terrestrial animals
Systemic circulation moves blood from heart to body, pulmonary circulation moves blood from heart to lungs
Amphibians and most reptiles have three-chambered hearts
Birds and mammals have four-chambered hearts
In three-chambered hearts, left atrium receives oxygen-rich blood, right atrium receives oxygen-poor blood
Fig. 4 shows comparative circulatory systems of different vertebrate species
The Mammalian Heart:
Mammalian heart is a four-chambered heart with two atria and two ventricles
Valves between chambers facilitate one-directional blood flow
Tricuspid valve between right atrium and ventricle, mitral valve between left atrium and ventricle
Additional valves facilitate blood flow away from the heart
Right chambers accept deoxygenated blood, left chambers accept oxygenated blood
Fig. 5 shows the flow of blood inside the mammalian heart
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Diagram of the flow of blood
(a) Blue - deoxygenated blood
(b) Violet - blood subjected to gas exchange
(c) Red - oxygenated blood
The Blood Vessels
The Arteries
Responsible for carrying blood away from the heart
Majority of arteries carry oxygenated blood, except for the pulmonary artery which carries deoxygenated blood
Arteries have thick layers of elastic fibers, smooth muscle, and tough inelastic connective tissue to adapt to high pressure
Elastic fibers allow arteries to stretch during the surge of blood when it exits the heart
The Capillaries
Serve as the link between the artery and vein
Capillaries have a single layer of endothelial cells, allowing for diffusion of materials
Capillaries form a vast network for efficient transportation of nutrients
The Veins
Responsible for transporting blood towards the heart
Majority of veins carry deoxygenated blood, except for the pulmonary veins which carry oxygenated blood towards the heart
Veins are larger in diameter, thinner walled, and have fewer elastic fibers compared to arteries
Blood flow in veins has lesser pressure
The Lymphatic System
Composed of thin-walled vessels that arise as lymph capillaries in the tissues
Functions include returning excess interstitial fluids to the blood and playing a role in the defense of the body
Lymph nodes contain defense cells such as macrophages and lymphocytes
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Self-test Questions
1. What is systemic and pulmonary circulation?
Systemic circulation: Blood flow from the heart to the body tissues and back to the heart
Pulmonary circulation: Blood flow between the heart and the lungs
2. Create a flowchart showing blood flow in closed and open circulation.
3. How does the heart of a frog, human, and shark differ from one another?
4. Identify the parts of the heart.
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Multiple Choice Questions
1. What is the circulatory system?
The body's blood-transporting system
2. From what source do cells get their food?
Other cells
3. Why is oxygen important to blood and cells?
Oxygen is necessary for cell growth and energy
4. Which type of blood vessels carries blood away from the heart?
Arteries
5. Why is blood that flows from the lungs to the heart bright red?
Oxygen makes it red
6. What part of the blood carries minerals, vitamins, sugar, and other foods to the body's cells?
Plasma
7. What is the main job of red corpuscles in the blood?
To transport oxygen to the body's cells and carry away carbon dioxide from the cells
8. What can best be compared to soldiers?
Red blood cells
9. Which element in the blood is round and colorless?
White blood cells
10. What would happen to people whose blood did not clot naturally?
They may bleed to death
11. What happens when a clot occurs in an undamaged blood vessel?
The flow of blood to tissues beyond the clot may be cut off
12. What happens to blood when it is pumped into the thin-walled blood vessels of the lungs?
Carbon dioxide is replaced with oxygen
13. What is the function of blood vessels and capillaries?
They carry blood to all parts of the body
14. Why does blood turn dark red as it circulates through the body?
The oxygen in it is replaced with carbon dioxide
15. How many major types of blood have scientists discovered?
Four: Types A, B, AB, and O
Page 21: Chapter 12. Animal Excretion / Urinary System Overview
Organisms need to excrete metabolic wastes to maintain life
Wastes include carbon dioxide, water, nitrogenous wastes, and mineral salts
Excretory system functions:
Collect water and filter body fluids
Remove and concentrate waste products from body fluids
Return necessary substances to body fluids for homeostasis
Eliminate excretory products from the body
Learning objectives:
Define and identify the importance of excretion
Classify different types of excretory systems in lower animals
Name different structures in the excretory organ of lower animals
Differentiate vertebrate and invertebrate excretion
A. Invertebrate excretory systems
Invertebrates generally conform to the principles of excretion
Aquatic forms excrete ammonia through diffusion
Terrestrial forms convert ammonia to uric acid
In aquatic forms, excretory organs are important for the composition of body fluids
Marine invertebrates have body fluids with the same concentration as seawater
Differences in ion proportions, more potassium and less magnesium
Freshwater invertebrates have dilute urine to conserve salt content and eliminate excess water
Some invertebrates have no organs for excretion, excrete nitrogen through diffusion
Five main types of invertebrate excretory organs:
Contractile vacuole
Nephridium
Renal gland
Coxal gland
Malpighian tubule
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The contractile vacuoles of protozoans
Protozoan animals have contractile vacuoles for osmotic regulation, not nitrogen excretion
More frequent and active in freshwater species than marine species
Contractile vacuole fills and empties, regulating cell volume
Fluid eliminated by the vacuole is more dilute than the cytoplasm
The nephridia of annelids, nemertines, flatworms, and rotifers
Nephridium refers to excretory organs of annelids and other phyla with similar characteristics
Annelids typically have a pair of nephridia on each segment
Nephridia are fine tubules that open into the body cavity or externally
Some annelids have solenocytes or flame cells instead of tubules opening into the body cavity
Non-segmented phyla also have tubules opening at the surface and ending in flame cells
Main excretory product is ammonia, but the route of excretion is not well-known
Earthworm nephridium is longer and more complex than marine annelids
Fluid enters the nephridium and its composition is modified along the tubule
Salts are reabsorbed, resulting in progressively more dilute fluid
Dilute urine passes into the bladder and exits through the nephridiopore
Earthworms can excrete urine up to 60% of their body weight in 24 hours
The renal glands of mollusks
Renal gland anatomy varies among mollusk classes
Renal gland is a wide tube opening from the pericardium to the mantle cavity
Single pair of renal glands, one member may be reduced or absent
Clams have the simplest arrangement
Renal glands help with excretion and are connected to the heart and mantle cavity
Page 23: Mollusks and Arthropods Excretory Systems
Mollusks excrete nitrogen as ammonia, except for octopuses which excrete nitrogen as ammonium chloride concentrated in urine.
Terrestrial snails and slugs excrete uric acid but may also excrete ammonia in moist surroundings.
Primary process in urine production in mollusks is filtration of the blood.
Freshwater mollusks reabsorb salts in the glandular tube and wide tubule, resulting in more dilute urine than blood.
Marine mollusks have urine with the same concentration as blood, but different ionic composition.
Coxal glands are tubular organs in aquatic arthropods, opening on the basal region of a limb.
Ancestral arthropods likely had a pair of coxal glands in every segment of the body.
Modern crustaceans usually have a single pair of glands opening at the bases of the antennae.
Antennal gland is a compact organ with a tubule comprising several recognizable regions.
Primary process in urine production is filtration of the blood through the wall of the coelomic sac.
Lobsters and marine crabs have urine with the same ion concentration as blood.
Freshwater crayfishes reabsorb urine in the canal, resulting in very dilute urine.
Freshwater crabs have decreased water permeability, slow water entry, and negligible salt loss via urine.
Some semiterrestrial crabs produce urine more concentrated than blood.
Concentrations of ions in blood and urine differ in all crustaceans analyzed.
Antennal glands coordinate with salt uptake by body surface cells for homeostasis.
Antennal glands in crustaceans seem unimportant for nitrogenous excretion.
Page 24: Insects Excretory System and Vertebrate Excretory Systems
Insects have malpighian tubules that end blindly in the body cavity and open to the alimentary canal.
Primary urine from malpighian tubules passes through the rectum, where its composition changes.
Insect excretory system comprises malpighian tubules and rectum working together.
Primary urine in malpighian tubules is formed by secretion, with potassium ions actively transported from the blood.
Water follows ions, and other substances like sugars, amino acids, and urate ions enter the primary urine.
Primary urine, along with digestion products and indigestible matter, passes to the rectum.
In the rectum, urine is acidified, soluble urate is converted to insoluble uric acid, and water and useful substances are reabsorbed.
Insects in dry surroundings have a rectum with remarkable reabsorption abilities, resulting in hard, dry pellets of solid uric acid.
Excretory system activity in insects is under hormonal control, demonstrated in the case of Rhodnius.
In mammals, the kidney and associated ducts are the excretory system, excreting nitrogenous waste as urea.
Birds, reptiles, and amphibians also have kidneys as excretory organs.
Fishes have narrow bands of tissue as kidneys, and their main excretory product is ammonia.
Page 25: Mammals
The mammalian kidney has two distinct regions: cortex and medulla.
The functional unit of the kidney is the nephron, which consists of four regions.
The nephron starts as a small vesicle called Bowman's capsule in the cortex.
The proximal convoluted tubule is continuous with Bowman's capsule.
The loop of Henle descends into the medulla and then runs up to the cortex as the distal convoluted tubule.
A collecting tubule courses through the medulla and opens into the pelvis of the kidney.
Urine formation involves three processes: filtration, reabsorption, and secretion.
Filtration allows all molecules below a certain size to pass into the primary urine.
Reabsorption and secretion involve specific mechanisms for the transport of specific substances.
The glomerular capillaries allow the passage of water and all constituents of the blood plasma except proteins.
The pressure of the blood in the glomerular capillaries is higher than in other parts of the kidney, ensuring a rapid flow of fluid into Bowman's capsule.
As the glomerular filtrate passes through the tubules, water and substances are reabsorbed into the blood.
The remaining fluid, called urine, reaches the pelvis of the kidney and contains nitrogenous waste.
Page 26: Birds and reptiles
Birds and reptiles excrete uric acid as their main excretory product.
Their urine is not highly concentrated and is conducted to the cloaca, not a urinary bladder.
Birds have salt glands that remove excess salt from their bodies.
Salt glands enable marine birds to drink seawater without ill effects.
Page 26: Amphibians
Amphibians excrete nitrogen in the form of urea and cannot produce urine more concentrated than the blood.
Their skins are permeable to water, causing water loss on land and water entry in fresh water.
Amphibians excrete a large volume of dilute urine in fresh water to counteract water entry.
When on land, amphibians conserve water by reducing glomerular filtration and releasing antidiuretic hormone.
Antidiuretic hormone increases the permeability of tubules and bladder to water, allowing reabsorption of stored urine.
Page 26: Fishes
Freshwater fishes produce a relatively large amount of dilute urine to remove water but lose salts.
Specialized cells in the gills take up diluted salts from fresh water and transport them into the blood.
Nitrogenous excretion in fishes is mostly ammonia, which is carried away in dilute urine or diffuses through the gills.
Marine fishes have a lower salt content in their blood compared to seawater, causing water loss and salt gain.
The kidneys of marine fishes cannot excrete urine more concentrated than the blood.
Marine bony fishes replace lost water by swallowing seawater and reject salt through special gill cells.
Sharks and rays convert ammonia to urea, which plays an important role in homeostasis.
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Osmotic and ionic regulation in fishes is under hormonal control.
Studied in fishes like eels and salmon that can move between fresh water and seawater.
Evolution of the vertebrate excretory system.
Studies of embryonic development show excretory system arises from a series of tubules.
Tubules constitute the archinephros, the ancestral form of the kidney.
Tubules open into a longitudinal duct, the archinephric duct.
Tubules lose internal openings and most anterior tubules degenerate in adults.
Ducts and tubules also serve the reproductive function and are called the urogenital system.
Greater sharing of function in males than females.
In reptiles, birds, and mammals, there is separation of function.
Blood composition in marine and freshwater animals.
Blood of marine animals is almost identical to seawater.
Blood of freshwater animals has about half the concentration of seawater.
Early freshwater fishes had blood osmotically equivalent to half-strength seawater.
Sharks and rays evolved urea retention when returning to the sea.
Bony fishes solved the problem by swallowing seawater and rejecting excess salt at the gills.
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Self-test questions:
Tubular organs opening on the basal region of a limb.
A wide tube opening from a sac surrounding one end of the heart to the mantle cavity.
Era when bony fishes returned to the sea.
Main excretory product of reptiles and birds.
In mammals, most nitrogenous waste are _____.
Filtration, ______, and secretion are processes in urine formation.
Structures that function as excretory and osmoregulatory organs in insects.
Amphibians excrete nitrogen in the form of ______.
Refers to an organism's ability to regulate physiological processes to maintain internal balance.
Internal opening through which body fluid enters the nephridium.
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Chapter 13. The Human Urinary System
Importance of kidneys in human excretion.
Structures and functions of kidney parts.
Sequence of urine formation.
Components of normal urine.
Symptoms and management of common urinary system disorders.
Importance of a healthy urinary system following a healthy diet and lifestyle.
A. The Kidneys
Kidneys, ureters, bladder, and urethra make up the urinary system.
Nephron is the kidney's functional unit.
Kidneys contribute to homeostasis by regulating blood and interstitial fluid composition.
Functions of the kidneys:
Remove wastes, toxic substances, and excess materials from the body.
Maintain appropriate concentrations of water and ions.
Regulate volume of blood and interstitial fluids.
Ensure optimal pH of body fluids.
Kidneys surrounded by fibrous capsule and perirenal fat.
Renal fascia and pararenal fat also present.
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Arterial supply to the kidney is through the renal artery, a branch of the aorta
Renal artery divides into five segmental arteries that enter the hilus of the kidney
Lobar arteries arise from each segmental artery, one for each renal pyramid
Interlobar arteries run toward the cortex on each side of the renal pyramid
Arcuate arteries arch over the bases of the pyramids
Renal vein emerges from the hilus in front of the renal artery
Lymph vessels follow the renal artery to lateral aortic lymph nodes
Nerves to the kidney originate in the renal sympathetic plexus
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Nephron consists of a capsule containing capillaries and the glomerulus, and a renal tube
Nephron has three functions: glomerular filtration, tubular reabsorption, and tubular secretion
Nephrons filter 125 ml of body fluid per minute, producing 180 liters of filtrate in 24 hours
178.5 liters of the filtrate are reabsorbed, while 1.5 liters form urine
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Urine is the liquid product containing nitrogenous wastes
Normal urine is approximately 95% water
Other components of normal urine are solutes, including organic molecules and ions
Organic molecules in urine include urea, creatinine, uric acid, and other substances
Ions in urine include sodium, potassium, chloride, magnesium, calcium, ammonium, sulphates, and phosphates
Other human excretory organs include the lungs, liver, and skin
Self-Test:
Functional unit of the kidney and the nephridium’s evolutionary modification: Nephron
A vertical slit bounded by thick lips of renal substance: Hilus
Contains the nitrogenous wastes of metabolism: Urine
This molecule is a common part of kidney stones and has a tendency to crystallize: Uric acid
Through what artery does blood flow into the kidney? Renal artery
How many segmental arteries enter the hilus? Five 7-8. Molecules in the liver that are by-products of the breakdown of proteins: Urea and uric acid
Organ that removes wastes and extra fluid in the body: Kidney
It transports urine from the renal