Write detailed answers of the following questions
(i) Describe structure of human heart with suitable diagram.
STRUCTURE OF HUMAN HEART
- Heart is the major organ of Circulatory system. It is a muscular pump which keeps the blood circulating throughout the body.
- It is enclosed in a fibrous bag like protective cover called Pericardium.
- The space between pericardium and heart is pericardial cavity which is filled with a fluid called pericardial fluid.
- This fluid reduces friction and Pericardium protects the heart, prevent it from over extension.
INTERNAL STRUCTURE OF HUMAN HEART
- Internally, it consists of four chambers, the upper two are thin walled called atria (sing: artrium) the lower two are thick walled called ventricles.
- Atria are completely separated from each other by a septum called interatrial septum.
- Similarly, the two ventricles are also separated from each other by a muscular partition called inter-ventricle septum.
- The right atrium and right ventricle are connected by Tricuspid Valve. Similarly, left atrium and left ventricle are connected by bicuspid valve.
- These valves prevent the backward flow of blood from the ventricles to the atria. Two main blood vessels are arising from ventricles to carry blood from heart to all parts of the body.
(ii) What is blood? Explain composition of blood and function of corpuscles.
BLOOD
Blood is a special type of tissue, found in the form of fluid which circulates in the body. It transports substances in the body of an organism.
COMPONENTS OF BLOOD
There are many cellular structures in the composition of blood. When a sample of blood is spun in a centrifuge machine, they separate into the following constituents: Plasma, buffy coat and erythrocytes.
PLASMA
The liquid state of blood can be contributed to plasma as it makes up ~55% of blood. It is pale yellow in color and when separated, it consists of salts, nutrients, water and enzymes. Blood plasma also contains important proteins and other components necessary for overall health.
RED BLOOD CELLS (RBC)
Red blood cells consist of Hemoglobin, a protein. They are produced by the bone marrow to primarily carry oxygen to the body and carbon dioxide away from it.
WHITE BLOOD CELLS (WBC)
White blood cells are responsible for fighting foreign pathogens (such as bacteria, viruses, fungi) that enter our body. They circulate throughout our body and originate from the bone marrow.
PLATELETS
Tiny disc-shaped cells that help regulate blood flow when any part of the body is damaged, thereby aiding in fast recovery through clotting of blood.
Explain transport of water and food in stem?
TRANSPORT OF WATER AND FOOD IN STEM
There are two types of transport tissues in plants.
XYLEM (WOOD):
In flowering plants xylem is made up of four type of tissues but the main tissues are the xylem vessels. A xylem vessel is a long, hollow, tubular structure from root to leaf. It is made up of many dead cells arranged vertically. The walls of these vessels become strong by the deposition of chemical substance called lignin.
PHLOEM (BAST):
Like xylem, phloem is also made up of four type of tissues but mainly consist of sieve tubes and companion cells. Phloem conducts manufactured food (sucrose) from part of plant where it is synthesized in high quantity to other parts of plant where it is required. The cross walls look like a sieve and therefore called sieve plates.