Aim: How do we eliminate metabolic wastes? Human Excretory System

Excretion Removal of wastes as a result of cellular metabolism of the activity of cells. A.If metabolic wastes are not removed from the organism, it will die. B.Also removes excess heat from body maintaining homeostasis.

The Wastes of Metabolism Metabolic ActivityWaste Produced Respiration CO2 & H2O Dehydration Synthesis H2O Protein Metabolism (breakdown) Nitrogenous wastes (ammonia, urea, uric acid) produced by the breakdown of amino acids Other activities Mineral salts (sodium chloride, potassium sulfate)

Human Excretory System A.Humans have a highly developed excretory system. B.Consists of the organs: 1.Lungs 2.Liver 3. Skin 4. Urinary system

Lungs A.Considered part of the excretory system because they get rid of CO2. which diffuses from the capillaries into the alveoli which is removed during exhalation. B. H2O diffuses into alveoli and removed during exhalation. C. CO2 and H2O are both waste products of aerobic respiration.

Liver A.Disposal of hemoglobin and bile formation. 1.Bile is made up of salts, cholesterol and part hemoglobin. 2. Secreted into small intestine where it helps in digestion of fats. Most bile is reabsorbed. Bile that is not absorbed passes through large intestine and removed as solid waste.

Liver B.Disposal of nitrogenous waste. 1.Amino acids that cannot be stored are broken down in liver (nitrogenous wastes). 2.It is in the form of urea (NH 3 & CO 2 ). 3.Urea is absorbed into the blood & removed by the kidneys as part of urine.

Liver C.Detoxification — the removal of harmful substances such as bacteria, certain drugs & hormones from the blood. 1. Within the liver these substances are changed into inactive or less poisonous form.

Skin A.Made up of many different kinds of tissues & performs a number of functions. B.Structure of skin: 1. Epidermis — outer layer of skin formed of layers of tightly packed cells. Contains a tough, water-proof protein called keratin. 2. Dermis — inner layer of skin located below epidermis.

Skin C.Functions of skin. 1. Protects internal tissues from injury & infection. 2. Contains nerves to detect pain, touch, pressure, and temperature changes.

Skin 3.Helps regulate body temperature by excreting a small amount of urea, salt & H2O through sweat glands. a. If body becomes warm: blood vessels become dilated, supply of blood increases (gives flush appearance) & heat is radiated through skin to air, increased sweating occurs, sweat evaporates and body is cooled. b. If body becomes cold: blood vessels in skin narrow slightly, reducing supply of blood, sweat less, allowing less heat loss from body. Muscle tension & shivering.

Structure of the Skin

Urinary System Made up of kidneys, ureters, bladder & urethra. A.Kidneys — pair of organs that excrete nitrogenous wastes & regulate the bloods chemical balance. Produce urine. 1. Two bean shaped organs found in the lower back region.

Urinary System 2. Kidneys contain 3 distinct regions: cortex, medulla & pelvis. a. Cortex — outer layer which contains nephrons that filter blood. b. Medulla — middle region which is made up of collecting ducts. c. Pelvis — inner region that connects with ureter.

Pelvis Structure of the Kidney

Urinary System B.Functional unit of the kidney called nephron which is made up of several regions. 1. Glomerulus — group of capillaries that form a tight ball. 2. Bowman’s capsule — encloses the glomerulus & collects wastes from capillaries. 3. Loop of Henle — reabsorption of useful substances. 4. Renal tubules — long tube that empties into a collecting duct.

Urinary System C.Urine is made in the nephron. The function of the nephron is filtration & reabsorption. 1. Filtration — H2O, salts, urea, amino acids & glucose are filtered from the blood. Glomerulus  Bowman’s capsule. 2. Reabsorption — reduces the volume of filtrate & returns useful substances to the blood such as some H2O, salts, amino acids, and glucose. These substances are actively transported into the capillaries surrounding the tubule at the Loop of Henle.

Urinary System 3. Urine is the fluid that reaches the end of the renal tubule & into the collecting tubes that will leave the kidney to the urinary bladder.

Nephron

Urinary System D.Ureter — tube that carries urine from the kidney to the urinary bladder. E.Urinary bladder — storage of urine. F.Urethra — tube that leads to the outside of the body.

Urinary System

Excretory System Disorders A.Kidney stones — substances that crystallize out of the urine in the urinary tract or kidney. B.Nephritis — an infection that may lead to kidney damage or failure.

Excretory System Disorders C.Gout — production & deposition of uric acid in joints. Symptoms are similar to arthritis. D.Jaundice — yellow color when bile is not excreted properly.

Excretory System Disorders E.Cirrhosis — overload of harmful materials from blood. F.Dialysis — artificial kidney machine that filters blood.

Excretory System Disorders G. Uremia- accumulation of metabolic wastes in the blood due to kidney filtration failure.