1. why do animals and humans have circulatory system??
2. what will happen,if the walls of arteries are not thick and elastic??
3. what are the small units that a kidney is made up of??
4.what do you understand by a heart beat??
Answers
Answer:
1. In an open circulatory system, blood vessels transport all fluids into a cavity. When the animal moves, the blood inside the cavity moves freely around the body in all directions. The blood bathes the organs directly, thus supplying oxygen and removing waste from the organs.
2. Arteries are the first vessels that carry blood from the heart and transport it to all the parts of the body. Since they must receive the blood directly from the heart which pumps the blood at a pressure sufficient to enable circulation, they need thick and elastic walls to both sustain the pressure (and so keep the blood flowing) and to withstand the pressure (and not get affected by the pressure).
The elasticity is what sustains the blood flow by enabling the arteries to expand and contract rhythmically with the systolic and diastolic pressure of the heart.
The thickness prevents tearing of the artery walls by the pressure of the blood.
3.The artery then branches so blood can get to the nephrons (pronounced: NEH-fronz) — 1 million tiny filtering units in each kidney that remove the harmful substances from the blood. Each of the nephrons contain a filter called the glomerulus (pronounced: gluh-MER-yuh-lus).
4. A pulsation of the heart, including one complete systole and diastole.
Explanation:
1.Animals and humans are multicellular animals. To transport the digested food material(nutrients)
and oxygen. If circulatory system is absent it take 3 years to reach the oxygen from our lungs to toe of feet.
The above line is mentioned in NCERT.
2. If arteries are thin walled the will burst when the heart apply pressure to transport the blood.
3. Small units of kidney are called nephrons.
4. The rythemic contraction and relaxation of heart is called a heartbeat
IF YOU ARE ASKING SUCH A LARGE QUESTION THEN PLEASE GIVE 15 0R 20 MARKS BECAUSE IT CONTAINS FOUR QUESTIONS.