A&P Excretory System

Excretion

The process of removing metabolic wastes. Must cross a cell membrane to leave the body. Just as important as digestion in maintaining the body's internal environment. 

Elimination

Removal of waste and undigested food material from the body.

Food Intake

Digestion -> Absorption -> Utilization of Nutrients by Cells -> Metabolic Wastes -> Excretion 

Metabolic Wastes

Byproducts of metabolism

Metabolism

The sum total of all the chemical reactions that keep an organism alive.

3 Metabolic Wastes

Water, Carbon Dioxide, Nitrogenous Wastes

3 Nitrogenous Wastes

Urea, Ammonia, Uric Acid.

Highly toxic. During the breakdown of amino acids the nitrogen-containing amino groups are removed (deamination) and converted to…

Ammonia

Urea

Principle nitrogenous waste product in humans. Produced in the liver from ammonia. Far less toxic than ammonia and can accumulate in higher concentrations without causing tissue damage.

4 Excretory Organs

Lungs, Liver, Skin, Kidneys

Lungs

Primary site of carbon dioxide excretion. Carries out detoxification, altering harmful substances so they aren’t poisonous. Also responsible for the excretion of the volatile (turning to vapor) substances in onions, garlic, and other spices.

Liver

Largest gland in the human body. Some proteins and other nitrogenous compounds are broken down here by deamination. As a result of these reactions, urea is formed. Produces bile, helps breakdown (emulsify) lipid molecules and old red blood cells. Responsible for maintaining “normal” levels of glucose in blood. Also responsible for removing potentially hazardous chemicals from the blood. It detoxifies the blood.

Skin

Excretes water and excess minerals (calcium, potassium, sodium) through perspiration. Sweat comes out of pores in skin, mixture of 3 metabolic wastes (water, urea, salts). 

Kidneys

Primary organs of the excretory system. Plays a vital role in maintaining the homeostasis of body fluids, they do this by adjusting the salt and water content of urine. Central component of urinary system. Excrete nitrogenous wastes such as urea, uric acid, and ammonium. Maintain blood volume by regulating amount of water excreted. Monitor blood composition by regulating electrolyte excretion. The kidneys monitor blood pH chiefly by regulating the excretion of certain ions, such as hydrogen (H+). NOTE: pH of blood  \~ 7.4.

Renin

Kidney secretes this enzyme which helps maintain blood pressure.

Erythropoietin

Kidney secretes this growth factor which stimulates red blood cell production.

Urinary System is composed of (4 structures)

2 Kidneys, 2 Ureters, 1 Bladder, 1 Urethra

Kidneys are what type of organ

Paired

Color of Kidney and size

Each kidney is a bean-shaped, reddish-brown organs about the size of a fist.

Location of Kidney

Lie on either side of the vertebral column in a depression high on the posterior wall of the abdominal cavity

Which Kidney is higher

The left kidney is usually 1.5 – 2.0 centimeters higher than the right kidney.

Why is the left Kidney higher

The liver is on the right side so the kidney needs to be lower on the right side.

3 Main Parts of the Kidney

Renal Cortex, Renal Medulla, Renal Pelvis

Renal Cortex

Outermost region of the kidney

Renal Medulla

Inner portion of the kidney (forms striped, cone-shaped regions called renal pyramids)

Renal Pelvis

Funnel-shaped structure in center of kidney (collects urine made by kidney).

Blood enters Kidney through this

Renal Artery

Renal Artery

Responsible for transporting nutrients and wastes to the kidneys. The nutrients are used by kidneys cells to carry out their life processes.

Renal Vein

Blood leaves Kidney through this

What is removed from the kidneys by urine

Toxins, urea, water, and mineral salts

Nephron

Functional unit of the Kidney, contain more than one million each

What do Nephrons do

These tiny filtering units remove urea from the blood and produce urine, which is transported through a collecting duct to the renal pelvis.

Parts of the Nephron

Bowman’s Capsule, Glomerulus, Renal Tubule

Bowmans Capsule

Cup-shaped structure that encloses a bed of capillaries

Glomerulus

Capillary bed cluster, that receives blood from the renal artery

Renal tubule

Collecting duct, has 3 parts proximal convoluted tubule, Loop of Henle, and the distal convoluted tubule

From the Kidneys, urine travels down 2 thin tubes called

Ureters

After urine is formed, it passes through

The nephrons and down the renal tubules of the kidney.

Ureters length

8-10 inches long

Ureter function

Convery urine from the kidney to the bladder.

What causes urine to enter the bladder even if the person is laying down

Peristaltic contractions

Urinary Bladder shape

A hollow muscular organ shaped like a balloon. Is held in place by ligaments that are attached to other organs and the pelvic bones.

Function

Stores urine until it is time to be eliminated 

Urinary Bladder holds

600 ml (1 pt.) of urine and becomes overdistended at 750 ml.  You get the urge to void at approximately 250 ml and you become uncomfortable at approximately 500 ml.

Nerves in bladder

Alert a person when it is time to urinate, or empty the bladder.

Bladder Sphincters

Help keep urine from leaking.These muscles close tightlyaround the opening of the bladder into the urethra, the tube that allows urine to pass outside the body. When you urinate, the brain signals the bladder muscles to tighten, squeezing urine out of the bladder. At the same time, the brain signals the sphincter muscles to relax.

Urethra

A thin-walled tube that extends from the bladder to an external opening called the external urethral orifice.

Male Urethra

8 inches 

Female Urethra

1\.6 inches

Why are females more likely to get a UTI

The short length of the female urethra 

Another name for Urination is

Micturition 

Amount of urine releases per day

Eliminates from 1.5 L to 2.3 L of urine per day. 

What affects amount of urine released

Depending on the amount of water taken in and the amount of water lost through respiration and perspiration.

Percentages of urine

95% water 5 % nitrogenous wastes and excess electrolytes. 

pH of urine

Varies between 4.8-7.5

Urinanalysis

Diagnostic tool that involves the physical, chemical and visual examination of urine

What does Urinalysis indicate

If any abnormal substances are present in the urine and is used to diagnose illness. May provide more information about the general condition of the body than other set of tests.