Transportation and Excretion

Transportation

A cell creates both useful and waste compounds throughout metabolism. While toxic molecules must be removed, useful substances must be transferred to other cells. This is done by the process of transportation.

Transportation in Human beings

  • Transportation in humans is occurs through the circulatory system.
  • The circulatory system in humans mainly composed of blood, blood vessels and the heart.
  • Blood transports food, oxygen, and waste materials in our bodies.
  • Blood consists of fluid medium called plasma in which the cells are suspended.
  • Plasma transports food, carbon dioxide, and nitrogenous wastes in dissolved form.
  • Oxygen is carried by the red blood corpuscles.
  • For transportation in human we thus need –
  • a pumping organ (heart) to push blood around the body,
  • a network of tubes (arteries and veins) to reach all the tissues and
  • a system in place (platelets) to ensure that this network can be repaired if damaged.

Heart – Our Pump

  • The heart is the body's primary pumping organ, and it is a muscular organ that is situated in the thoracic area, somewhat to the left of the chest.
  • The four chambers that make up the human heart are responsible for moving both oxygenated and deoxygenated blood.
  • The upper two chambers are called atria, whereas the lower two chambers are called ventricles.
  • Oxygen-rich blood from the lungs comes to the thin-walled upper chamber of the heart on the left, the left atrium.
  • The left atrium relaxes when it is collecting this blood.
  • It then contracts, while the next chamber, the left ventricle, relaxes, so that the blood is transferred to it.
  • Blood is pumped out to the body as each muscular left ventricle contracts.
  • The right atrium, the higher chamber on the right, receives deoxygenated blood from the body when it relaxes.
  • As the right atrium contracts, the corresponding lower chamber, the right ventricle, dilates.
  • Afterwards, the right ventricle pushes the blood to the lungs for oxygenation.
  • The separation of the right side and the left side of the heart is useful to keep oxygenated and deoxygenated blood from mixing. Such separation allows a highly efficient supply of oxygen to the body.

Double Circulatory System

  • The heart pumps the oxygenated blood it receives from the lungs back into the body's various organs.
  • Thus, the blood passed twice through the heart making one complete round through the body, i.e., once through the right half in the form of deoxygenated blood and once through the left half in the form of oxygenated blood.

Blood Vessels

  • Blood vessels carry blood throughout the body.
  • These three types of blood vessels are arteries, veins and blood capillaries.

 

Artery

Vein

Have thick, elastic, muscular walls.

Have thin, non-elastic walls.

Lumen of artery is narrow.

Lumen of veins is wide.

Carry blood from the heart to all body parts.

Carry blood from all body parts to the heart.

Blood flows under pressure through an artery.

Blood flow through vein is much calmer.

Carry oxygenated blood (except pulmonary artery).

Carry deoxygenated blood (except pulmonary vein).

 

Blood Pressure

  • Blood pressure is measured with an instrument called a sphygmomanometer.
  • The force that blood exerts against the wall of a vessel is called blood pressure.
  • This pressure is much greater in arteries than in veins.
  • The pressure exerted on the walls of arteries when the heart is filling with blood is called diastolic pressure. It constitutes the minimum pressure on arteries.
  • The pressure exerted on the walls of arteries when the heart is filling with blood is called diastolic pressure. It constitutes the minimum pressure on arteries.
  • The normal systolic pressure is about 120 mm of Hg and diastolic pressure is 80 mm of Hg.

Maintenance by platelets

  • In case of any leakage, the blood has platelet cells that circulate around the body and plug these leaks by helping to clot the blood at these points of injury.

Lymph

  • Lymph is similar to blood but RBCs are absent in lymph.
  • Lymph is formed from the fluid which leaks from blood capillaries and goes to the intercellular space in the tissues. This fluid is collected through lymph vessels and finally returns to the blood capillaries.
  • The functions of lymph in transportation are:
  • Lymph transfers digested and absorbed fat from the intestine back to the blood.
  • Lymph drains excess fluid from extracellular space back into the blood.
  • Blockage of the lymphatic system will result in water retention and ineffective fat absorption in the body.

Transportation in Plants

  • Transportation is a crucial process in plants.
  • The process involves the transportation of water and necessary nutrients to all parts of the plant for its survival.
  • In plants, the movement of food and water happen separately.
  • The xylem moves water and minerals obtained from the soil.
  • Phloem transports products of photosynthesis from the leaves where they are synthesized to other parts of the plant.

Xylem

  • It is conducting tissue which transport water and minerals from the roots to other parts of the plant
  • No energy is used during transportation.

Phloem

  • It is also a conducting tissue which transports products of photosynthesis from the leaves where they are synthesized to other parts of the plant.
  • Energy is used from ATP during transportation.

Transpiration

  • It is the process by which plants lose water in the form of vapours.
  • Role of Transpiration-Absorption and upward movement of water and minerals by creating PULL and helps in temperature regulation in Plant.

Translocation

  • Transport of food from leaves (food factory) to different part of the plant is called Translocation.
  • It occurs in the part of the vascular tissue known as the phloem.
  • Translocation in phloem is achieved by utilizing energy.
  • Material like sucrose is transferred into phloem tissue using energy from ATP.

Transport of water

  • Imbibition, osmosis, root pressure, and transpiration are the processes that contribute to the upward movement of water, even in the tallest plants.
  • Water is absorbed by the roots and carried via the xylem to the higher sections of the plant.
  • At the roots, cells in contact with the soil actively take up ions. This creates a difference in the concentration of these ions between the root and the soil. Water, therefore, moves into the root from the soil to eliminate this difference.
  • Evaporation of water molecules from the cells of a leaf creates a suction that pulls water from the xylem cells of roots.

Excretion in Human Beings

  • Excretion is the process by which organisms remove harmful metabolic wastes from the body.
  • Various metabolic processes generate a lot of wastes.
  • They must be eliminated rapidly because an organism's exposure to an accumulation of them in the body can be harmful or even fatal.

Human Excretory System

  • Human excretory system includes :
    • a pair of kidneys,
    • a pair of ureters,
    • a urinary bladder and
    • urethra.

Kidney:

  • The kidney is a bean-shaped organ that is located in the abdominal cavity close to the vertebral column
  • The kidney is made up of numerous filtering cells, called nephrons.
  • Nephron is called the functional unit of kidney.

Nephron

  • It is made up of a tangled mess of tubes and a filtering part, called glomerulus.
  • The glomerulus which is a network of blood capillaries to which the renal artery is connected.
  • The artery that delivers blood to the glomerulus is referred to as the afferent arteriole, and the artery that receives blood from the glomerulus is referred to as the efferent arteriole.
  • The glomerulus is enclosed in a capsule like portion, called bowman’s capsule. The bowman’s capsule extends into a fine tube which is highly coiled.
  • Tubes from various nephrons converge into collecting duct, which finally goes to the ureter.

 

Urine formation in the kidney: The urine formation involves three steps:

  • Glomerular filtration: Nitrogenous wastes, glucose, water, amino acid filter from the blood into bowman’s capsule of the nephron.
  • Tubular reabsorption: By the capillaries surrounding the nephron, useful chemicals from the filtrate are now again absorbed.
  • Secretion: Extra water, salts are secreted into the tubule which opens up into the collecting duct and then into the ureter.

 

The urine that the kidneys make travels down the ureters and into the bladder, where it is stored until it gets released by the urethra.

Haemodialysis: The process of purifying blood by an artificial kidney. It is meant for kidney failure patients.

Excretion in Plants

Plants use different strategies for excretion of different products:

  • Oxygen and carbon dioxide are diffused through stomata during photosynthesis.
  • Excess water is excreted by transpiration.
  • Plants can even lose some of their old parts like old leaves and the bark of trees.
  • Waste products stored as gums, resin in old Xylem
  • Plants excrete some waste into the soil around them.