The Excretory SystemBy: Joseph Martinez

Function of the Excretory System Removes harmful substances and waste materials that collect

in the body. Major Excretory Organs: Skin, Lungs, Liver, Large Intestines,

and Kidney.

Skin Layers and Function The Skin is the largest organ and covers the entire body. Three major layers: Epidermis, Dermis, and Subcutaneous. Excretory function- Removes waste materials absorbed by the sweat glands through the process of sweating or perspiration.

Helps to cool down the body.

Excretory Organ of Skin

Sweat Glands Found in the Reticular Layer of the Dermis. Two types of sweat glands- Apocrine and Eccrine sweat glands. Sweat glands function and structure- Store and release sweat through the excretory duct on the

surface of the skin during perspiration. Perspiration increases when exercising, fighting a fever and

when the weather is warm. Ducts are made up of simple and stratified cuboidal epithelium. Sweat glands are made up of columnar epithelium. Connective tissue surrounds the sweat glands.

Type of Sweat Glands Eccrine Sweat glands- Store sweat and release sweat through the excretory duct on to

the surface of the skin from the sweat pore. Found on most of body. Greater in thick skin -Palms of the hands and soles of the feet.

Type of Sweat Glands Apocrine Sweat Glands- Found under the armpits, and private areas of your body. Less apocrine glands than eccrine glands. Apocrine gland stores sweat and releases it out the excretory

duct which opens into the hair follicle. Secretes a thick substance which has an odor due to the

breakdown of bacteria.

Lungs Pair of organs found in the chest. Remove the waste material carbon dioxide from the body, during exhalation. Process of Breathing Respiratory center in brain receives message from nerves in

aorta and carotids that oxygen is low in the blood. Brain signals diaphragm, a muscle below the lungs, and

respiratory muscles to tighten which causes inhalation to occur when the muscles relax.

Inhalation- Oxygen is breathed in through upper airways into the lower airways, and then into the gas exchange airways.

Exhalation – Carbon dioxide is breathed out.

Liver Anatomy Largest Gland organ in the body. Found in chest under right diaphragm. Covered by Glisson’s capsule. Divided into two lobes: Right lobe and Left lobe. Excretory function The liver filters waste from the blood and it is taken to the

large intestine for removal from the body from the anal canal. Ammonia is broken down by the liver and made into urea

which is taken to the kidney for removal from the body through the urethra.

Liver – Excretory Function Blood supply from the intestines is brought to the liver

through the mesenteric vein, into the portal vein of the liver and into the sinusoids.

The blood supply includes Amino acids, sugars, small fatty acids, and harmful substances.

Hepatocytes help breakdown the substances through process called metabolic detoxification.

Large Intestine Cecum, appendix, colon, rectum, and anal canal. Colon: ascending, transverse, descending, and sigmoid. Chyme or undigested food is received from the small intestine

into the large intestine which becomes feces. Feces is made by removing water and adding mucous and is

released from the body through the anal canal or anus.

Kidneys Two bean shaped organs located on the back wall of the

abdomen space. Renal capsule covers both kidneys. Covered by fat and connective tissue. Removes waste materials from the body such as urea,

minerals, and excess water called urine.

Nephron Part of the Kidney that makes urine. 1.2 million nephrons in each kidney. Three types of NephronsSuperficial cortical nephron- Majority of the nephrons goes into a small portion of the medulla.Midcorticol nephrons- Have short or long loops. Juxtamedullary nephrons- Extend into the medulla and they are responsible for making the urine more concentrated.

Urine formationBlood enters the glomerulus through the afferent arteriole and leaves through the efferent arteriole. Urine is formed when the blood is filtered through the clefts or filtration membranes of the glomerulus.

Urine Excretion Urine flows from Bowman’s space into: Proximal tubule Loop of Henle Distal convoluted tubule Collecting ductsThe collecting ducts flow into : Calyxes- Minor and Major Renal pelvis Ureter Bladder Urethra and out of body

Disease of Excretory System Liver Cirrhosis- A disease that causes the liver to become tough, hard, and scarred. Damage can not be reversed. It occurs over a period of years. Leading cause of death in United States. Symptoms- Yellowing of the skin and eyes Abdomen swelling Abdomen pain Weight loss Weakness. Causes- Hepatitis, liver obstruction,and excessive alcohol or drug use.

Liver Cirrhosis Treatment- Steroids, drugs to slow the

hardening of the liver, stopping the drug or alcohol use, removing the obstruction, good nutrition, and rest.

Liver failure- Liver has failed, toxins build up in body, and the person would require a liver transplantation.

Prevention- Avoid drinking alcohol and taking drugs.

Quiz1. What are the two types of sweat glands?

2. What waste product does the lungs release?

3. The liver converts ammonia into what waste

product?

4. Urine is formed after it is filtered through what

part of the kidney?

5. What is the major cell type found in the liver

that is responsible for breaking down waste?

Answers1. Apocrine and Eccrine

2. Carbon Dioxide

3. Urea

4.Glomerulus

5.Hepatocyte

BibliographyEroschenko, V. P. (2000). Atlas Of Histology (9th Ed.). Baltimore, MD: Lippincott Williams and Wilkins. Huether, S. E, &McCance, K. L. (2006). Pathophysiology: The Basis for Disease in Adults and Children (5th Ed.). Philadelphia, PA: Elsevier Mosby. Paulsen, Douglas F. (2000). Histology and Cell Biology (4th Ed.). New York, NY : McGraw-Hill. http://www.brainpop.com/health/bodysystems/urinarysystem/