The Human Kidneys

The kidney are a pair of red-brown, bean-shaped organs. Each kidney is about the size of a first. The kidneys are covered and protected by thick layers of fats. A longitudinal section of the kidney shows that it is divide into two regions. The dark red outer region is called the cortex and the pale-red inner region is called the medulla. The medulla is filled with cone-shaped tissues called pyramids. The apices of the pyramids open into a funnel shapes cavity called the pelvis. The pelvis drains urine into the ureter.Each human kidney has at least one million tiny blood filters. Urine is formed within these tiny blood filters.

 

Functions of the kidneys

1. The kidneys remove nitrogenous waste products such as urea along with excess water and mineral salts in the form of urine
2. Kidneys keep the water and mineral contents in our body in balance
3. The kidneys control the amount of mineral salts in the body fluid
4. The kidneys also help to maintain the pH of blood and tissue fluid.

The Human Urinary System

The urinary system consists of a pair of kidneys, a pair of ureters, the urinary bladder and the urethra. Blood is carried to each kidney by the renal artery and away from it by the renal vein. The kidneys are located on either side of the spine at the back of the abdominal cavity. They lie just above the waistline and the left kidney is slightly higher than the right kidney.

Source : http://d75822.medialib.glogster.com/media/24/24b4ec59f2432d804f4086d2003506aa2e7e0c076133fdf0c7f17cec179bf1d2/excretory-system.jpg

The blood is filtered within the kidney. Waste products (urea) and excess substances (mineral salts and water) are converted into urine. The ureter carry the urine from the kidneys to the urinary bladder. The urinary bladder store urine and gradually expands like a balloon. When the muscles in the wall of the bladder contract, urine is expelled to the exterior via the urethra. This process is called urination.

Skin as Exretory Organ

The skin not only protects our body, but is also an excretory organ. The skin has many sweat glands which produce sweat when the body is hot. Each sweat gland is a long coiled tube. The sweat gland leads to a sweat duct which opens on the skin surface as a sweat pore. Sweat is extracted from the blood capillaries surrounding the sweat glands. Sweat contains water, mineral salt and urea.

Source : http://www.heartspring.net/images/skin_cancer_layers_748.jpg

The Transport System In Plant

The vascular tissues are concerned with transport and are functionally equivalent to the circulatory system of mammals. The two types of vascular tissues are called xylem and phloem.

The main function of the xylem is to transport water and minerals salt from the roots to the stem an leaves. Xylem forms wood in shrubs and trees. Therefore, xylem provides support to the plants. Xylem consists mainly of vessels, which are elongated tubes with thick walls. The walls are strengthened with a substance called lignin. Xylem vessels are dead structures without protoplasmic contents and transverse walls.

Source : http://cnx.org/content/m44708/latest/Figure_30_05_04.png

Phloem transport synthesised food substances from one part of the plant to another. Phloem consists mainly of sieve tubes. Sieve tubes are living cells without nucleus. The walls of sieve tubes are composed largely of cellulose. The transverse walls of sieve tubes are perforated by pores and are called sieve plates. Each sieve tube cell has a companion cell beside it.

Source : http://leavingbio.net/FLOWERING%20PLANTS_files/image048.jpg

Structure of Human Heart

The heart is a muscular organ with walls made of cardiac muscles. The coronary arteries supply nutrients and oxygen to the muscles while the coronary viens remove waste from the muscles.

Source : http://upload.wikimedia.org/wikipedia/commons/f/f5/Wiki_Heart_Antomy_Ties_van_Brussel.jpg

 The heart is divided into four chambers. the two upper chambers are called auricles or atria and the two lower chambers are called ventricles. The septum divides the heart into the right and left halves. The auricles have thinner walls than the ventricles. When the auricles contract, blood is pushed into the ventricles below. The left ventricle has a much thicker muscular wall than the right ventricle. The right ventricle pump blood to the lungs, which lie next to the heart. The left ventricle has pump blood from the heart to the rest of the body.

The right atrium is connected to the right ventricle by the tricuspid valve. The left atrium is connected to the left ventricle by the bicuspid or mitral valve. Semilunar valve are situated at the entrances of the aorta and the pulmonary artery to prevent the backflow of blood into the ventricles. The chordae tendineae prevent the valve from turning inside out when the ventricles contract.

Source : http://cnx.org/content/m46676/latest/2008_Internal_Anatomy_of_the_HeartN.jpg

The human blood

The human blood consist of a 55% of fluid called plasma and other 45% is cellular components consist of red blood cells, white blood cells and platelets. 

Source: http://www.yallatb.com/images_edit/47.jpg

Plasma is yellow liquid in our blood. 90% of plasma is water. The rest are dissolved substances which include nutrients such as glucose, amino acid and vitamins, proteins like antibody, hormones, enzymes, albumins and fibrinogen and inorganic ions such as sodium, calcium, chlorides and phosphates. Main function of plasma are to transport nutrients to tissue, to remove waste products from tissues, to distribute hormone, enzymes, antibodies and other proteins and to distribute heat energy from the liver and muscles to all other part of the body.

Red blood cell (erythrocytes) transport oxygen from the lungs to all parts of the body. They contain a red pigment called haemoglobin which combines with oxygen molecules to form oxyhaemoglobin. They also carry carbon dioxide from our body cells to our lungs. Red blood cells are made in the bone marrow. The lifespan of red blood cells is about 120 days. When red blood cells are worn out, they are destroyed in the liver and spleen.

Source: http://www.replenishingsoul.com/blog/wp-content/uploads/2009/12/red-blood-cells.jpg

White blood cells (leucocytes) are much larger than red blood cells and they each have a nucleus. They are usually irregular in shape, colourless and do not contain haemoglobin. There are several types of white blood cells. White blood cells are formed from bone marrow cells. The lifespan of white blood cells depends on the type of white blood cells. It varies from a few hours to a few months. They play a vital role in the body’s defence against diseases. Unlike red blood cells, white blood cells can squeeze through the walls of the blood capillaries into the space among the cells to destroy the bacteria.

Source: http://www.sciencephoto.com/images/download_wm_image.html/P248307-White_blood_cells-SPL.jpg?id=802480307

Platelets are cells fragments produced by large cells in the bone marrow. Under a high-powered microscope, they appear as under tiny oval-shape structures without nucleus. They play an importance role in blood clotting. When a blood vessel breaks, the platelets release clotting factors.

Source: http://jama.ama-assn.org/content/301/13/1329.2/F1.medium.jpg

The blood vessels

There are three types of blood vessels; arteries, veins and capillaries. Arteries are blood vessels which carry blood away from the heart. Arteries deliver oxygenated blood except the pulmonary artery. The walls of arteries are much thicker and stronger than those of veins because they have to withstand the high pressure of blood coming from the heart. Veins are blood vessels which carry blood back to the heart. Veins deliver deoxygenated blood except pulmonary veins. Veins are thinner walls than arteries because blood pressure in the veins is much lower than in the arteries. Since the blood in the veins may be moving against gravity, they contain valve to prevent the blood from flowing back. Capillaries are tiny blood vessels which connect arteries and veins. They have walls which are only one cell thick. Oxygen and nutrients move from the blood through the capillary walls into the body cells. At the same time, carbon dioxide and other waste products move from the cells into the blood.

Source: http://academic.kellogg.edu/herbrandsonc/bio201_mckinley/f23-1_walls_of_an_arter_c.jpg