Osmotic Regulation and Excretion

• Chapter 41 discusses Osmotic Regulation and Excretion in living things

Body Fluids

• Intracellular fluid is the fluid inside cells and makes up mosts of the body's fluid
• Extracellular fluid includes interstitial fluid, blood plasma, and lymph
• Serum separated from blood constitutes blood plasma, after removal of clotting factors

Circulatory and Excretory System Interface

• The circulatory system interacts with the excretory system

Lymphatic System

• Found in vertebrates, it is an accessory circulatory system
• Returns interstitial fluid to the blood
• Launches immune responses
• Absorbs lipids from the digestive tract
• Failure to return interstitial fluid to circulation can result in conditions like filariasis (elephantiasis), breast cancer-related issues, and uterine cancer-related problems

Solvent vs Solute

• These are the key components that make up solutions

Diffusion vs Osmosis

• These are two different forms of movement across barriers

Tonicity

• Isotonic, hypotonic, and hypertonic are terms used to describe the relative solute concentrations of solutions being compared
• Normal saline contains 0.9% sodium chloride (NaCl)
• The concentration of NaCl in saline is similar to blood and tears
• Tonicity refers to the ability of a solution to cause a cell to gain or lose water
• Cells placed in solutions of differing tonicity may not change, swell/burst (cytolysis), or shrink/shrivel (plasmolysis)

Passive vs Active Transport

• Water diffuses passively from high to low concentration across a semi-permeable membrane
• Some molecules get through special protein channels using facilitated diffusion
• Active transport uses ATP, carrier proteins, or pumps to move solutes against their concentration gradient

Cellular Respiration Equation

• Glucose + Oxygen → Carbon Dioxide + Water + ATP (C6H12O6 + O2 → CO2 + H2O + ATP)

Organic Precursors

• Simple sugars become carbohydrates
• Fatty acids and glycerides become lipids
• Amino acids become proteins
• Sugars, amines, and phosphates become nucleic acids (DNA, RNA)
• Organic precursors store carbon, hydrogen, and oxygen as glycogen in the liver and as fat

Waste Products of Cellular Respiration

• In addition to carbon dioxide and water, nitrogenous wastes from amino acids and nucleic acids
• Urea, uric acid, and ammonia are types of nitrogenous waste, uric acid crystals can cause gout and gallstones

Osmoregulation

• Regulating the concentration of water and salts to maintain body fluids at homeostatic levels
• Water and salt concentrations are maintained differently in different organisms

Nitrogenous Waste

• This refers to waste containing nitrogen from amino acids and nucleic acids

Waste Removal in Organisms

• Microorganisms like Amoeba and Paramecium use contractile vacuoles
• The tonicity of fresh water has implications for organisms living in it
• Flatworms use flame cells
• Earthworms use nephridia
• Insects and arthropods use Malpighian tubules
• Insects excrete waste as a thick paste or powder

Electrolytes

• These are minerals in the body with an electric charge, either positive or negative ions
• Sodium (Na+), calcium (Ca++), magnesium (Mg++), potassium (K+), chloride (Cl-), and phosphate (PO4-3) are electrolytes

Kidneys and Osmoregulation

• The kidneys filters about 180 liters per day, equivalent to 60 times the plasma volume
• The kidneys produces 800ml-2000ml urine per day
• The kidney has a renal cortex, renal medulla, and renal pelvis
• The functional unit of the kidney is the nephron, with kidney containing 200,000 to over 1.8 million nephrons
• Key structures in the nephron include the renal corpuscle (Bowman's capsule and glomerulus), proximal convoluted tubule, Loop of Henle, and distal convoluted tubule

Kidney Function Overview

• The hilum is a structure in the kidney that's involved in excretion and osmoregulation

Nephron

• The nephron is the kidney's functional unit
• The nephron includes a renal corpuscle

Urine Formation

• In urine formation, filtration occurs in the glomerulus
• Absorption happens in the renal tubules, with antidiuretic hormone (ADH) preventing water loss and aldosterone preventing the loss of sodium, potassium, and water
• Secretion, the opposite of absorption, also occurs in the renal tubules, involving urea, uric acid, creatinine (from muscle breakdown), and ions
• Excretion is the process of removing urine, which is 95% water

Urine Formation Processes

• Glomerular filtration filters water and solutes from blood into the nephron
• Tubular reabsorption moves useful substances from the filtrate into the blood
• Tubular secretion transports wastes and excess substances from blood to filtrate
• Excretion removes urine