TRANSPORTATION IN PLANTS AND CIRCULATION IN ANIMALS

Introduction

· Multicellular organisms possess millions of cells in their body.

· The bulk movement of substances through the vascular tissue is called Translocation.

· In larger organisms transport of nutrients, salts, oxygen, hormones and waste products around the body are performed by the ‘Circulatory system’.

· The circulatory system consists of the circulating fluids, the blood and lymph and the heart and blood vessels which form the collecting and transporting system.

Means of Transport in Plants

· The transport of materials in and out of the cells is carried out by diffusion and active transport in plants.

Diffusion

· The movement of molecules in liquid and solids from a region of higher concentration to a region of their lower concentration without the utilization of energy is called diffusion. This is a passive process.

Active Transport

· Active transport utilizes energy to pump molecules against a concentration gradient.

· These proteins use energy to carry substances across the cell membrane hence they are oft en referred to as pumps.

· These pumps can transport substances from a low concentration to a high concentration (‘uphill’ transport).

Osmosis

· Osmosis is the movement of solvent or water molecules from the region of higher concentration to the region of lower concentration through a semi-permeable membrane.

· This process is carried out till an equilibrium is reached. Osmosis is the passive movement of water or any other solvent molecules.

Plasmolysis

· It occurs when water moves out of the cell and resulting in the shrinkage of cell membrane away from the cell wall.

Imbibition

· Imbibition is a type of diffusion in which a solid absorbs water and gets swelled up. eg. absorption of water by seeds and dry grapes

· If it were not for imbibition, seedlings would not have been able to emerge out of the soil.

Root Hair-Water Absorbing Unit

· There are millions of root hairs on the tip of the root which absorb water and minerals by diffusion.

· Root hairs are thin walled, slender extension of epidermal cell that increase the surface area of absorption.

Pathway of Water Absorbed by Roots

· Once the water enters the root hairs, the concentration of water molecules in the root hair cells become more than that of the cortex.

· Thus water from the root hair moves to the cortical cells by osmosis and then reaches the xylem. From there the water is transported to the stem and leaves.

Types of Movement of Water into the Root Cells

Apoplast Pathway

· The apoplastic movement of water occurs exclusively through the intercellular spaces and the walls of the cells.

· Apoplastic movement does not involve crossing the cell membrane. This movement is dependent on the gradient.

Symplast Pathway

· In symplastic movement, the water travels through the cells i.e. their cytoplasm; intercellular movement is through the plasmodesmata.

· Water enter the cells through the cell membrane, hence the movement is relatively slower. Movement is again down a potential gradient.

Transpiration

· Transpiration is the evaporation of water in plants through stomata in the leaves.

· The opening and closing of the stomata is due to the change in turgidity of the guard cells.

· When water enters into the guard cells, they become turgid and the stoma open. When the guard cells lose water, it becomes flaccid and the stoma closes.

· As water is lost from the leaves, pressure is created at the top to pull more water from the xylem to the mesophyll cells, this process is called transpiration pull.

· Transpiration is affected by several external factors such as temperature, light, humidity, and wind speed.

· Internal factors that affect transpiration include number and distribution of stomata, percentage of open stomata, water status of the plant, canopy structure etc.

Importance of Transpiration

· Creates transpirational pull for transport of water.

· Supplies water for photosynthesis.

· Transports minerals from soil to all parts of the plant.

· Cools the surface of the leaves by evaporation.

· Keeps the cells turgid; hence, maintains their shape.

Root Pressure

· As ion from the soil are actively transported into the vascular tissue of the root, water moves along and increases the pressure inside the xylem.

· This pressure is called root pressure and is responsible for pushing water to smaller height of the stem.

Uptake of Minerals

· Plants depend on minerals from soil for its nutritional requirements.

· Two factors account for this: (i) minerals are present in the soil as charged particles (ions) that cannot move across cell membranes and (ii) the  concentration of minerals in the soil is usually lower than the concentration of minerals in the root.

Translocation of Mineral Ions

· Minerals are remobilised from older dying leaves to younger leaves.

· This phenomenon can be seen in deciduous plants. Elements like phosphorus, sulphur, nitrogen and potassium are easily mobilised, while elements like calcium are not remobilised.

Phloem Transport

· The food synthesised by the leaves are transported by the phloem either to the area of requirement or stored.

· Phloem transports food (sucrose) from a source to a sink.

· The source is part of the plant that synthesize food, i.e., the leaf, and sink, is the part that needs or stores the food. But, the source and sink may be reversed depending on the season, or the plant’s need.

· Since the source-sink relationship is variable, the direction of movement in the phloem can be upwards or downwards, i.e., bidirectional.

· In contrast, the movement is always unidirectional in xylem i.e., upwards.

Translocation of Sugars

· The mechanism of translocation of sugars from source to sink is through pressure flow hypothesis Glucose prepared at source (by photosynthesis) is converted to sucrose.

· Sucrose moves into the companion cells, then into the living phloem sieve tube cells by active transport.

· As osmotic pressure builds up, the phloem sap moves to areas of lower pressure. By active transport sucrose moves into the cells where it is utilised or stored.

· As sugars are removed, the osmotic pressure decreases and water moves out of the phloem.

Ascent of Sap and its Events – An Overview

· The upward movement of water and minerals from roots to different plant parts is called ascent of sap.

Blood

· Blood is the main circulatory medium in the human body. It is a red coloured fluid connective tissue.

White Blood Corpulses (WBC)

Blood Platelets or Thrombocytes

· These are small and colourless. They do not have nucleus. There are about 2,50,000 – 4,00,000 platelets / cubic mm of blood.

· Life span of platelets is 8–10 days. They play an important role in clotting of blood. Platelets form clot at the site of injury and prevent blood loss.

Functions of blood

i) Transport of respiratory gases (Oxygen and CO2).

ii) Transport of digested food materials to the different body cells.

iii) Transport of hormones.

iv) Transport of nitrogenous excretory products like ammonia, urea and uric acid.

v) It is involved in protection of the body and defense against diseases.

vi) It acts as buffer and also helps in regulation of pH and body temperature.

vii) It maintains proper water balance in the body

Blood Vessels - Arteries and Veins

· Arteries: They are thick and elastic vessels that carry blood away from the heart to various organs of the body.

· Veins: Veins are thin and non-elastic vessels that transport blood to the heart from the different organs.

· Capillaries: Capillaries are narrow tubes formed by branching of arterioles which then unite to form the venules and veins.

Differences between Artery and Vein

Artery	Vein
Distributing vessel	Collecting vessel
Pink in colour	Red in colour
Deep location	Superficial in location
Blood flow with high pressure	Blood flow with low pressure
Wall of artery is strong, thick and elastic	Wall of vein is weak, thin and non-elastic
All arteries carry oxygenated blood except pulmonary arteries	All veins carry deoxygenated blood except pulmonary veins
Internal valves are absent	Internal valves are present

Types of Circulatory System

Structure of Human Heart

· Heart is a muscular pumping organ that pumps out the blood into the blood vessels.

· The heart is made of specialized type of muscle called the cardiac muscle.

· The heart is enclosed in a double walled sac called pericardium.

· It contains lubricating pericardial fluid which reduces friction during heart beat and protects it from mechanical injuries.

· The human heart is four chambered. The two upper thin walled chambers of the heart are called auricle or atria and two lower thick walled chambers are called ventricles.

· The chambers are separated by partition called septum.

· The two auricles are separated from each other by interatrial septum.

· The right atrium receives deoxygenated blood from different parts of the body through the main veins superior vena cava, inferior vena cava and coronary sinus. Pulmonary veins bring oxygenated blood to the left atrium from the lungs.

· The two ventricles are separated from each other by an interventricular septum. The left and right ventricles have thick walls because the ventricles have to pump out blood with force away from the heart.

· From the right ventricle arises the pulmonary trunk which bifurcates to form right and left pulmonary arteries.

· The right and left pulmonary arteries supply deoxygenated blood to the lungs of the respective side. The left ventricle is longer and narrower than the right ventricle.

· The walls are about three times thicker than the right ventricle. The left ventricle gives rise to aorta. The oxygenated blood is supplied by the aorta to various organs of the body. The coronary arteries supply blood to the heart.

Valves: The valves are the muscular flaps that regulate the flow of blood in a single direction and prevent back flow of blood.

Types of Blood Circulation

· Systemic circulation

· Pulmonary circulation

· Coronary circulation

Heart Beat

· One complete contraction (systole) and relaxation (diastole) of the atrium and ventricles of the heart constitute heartbeat. The heart normally beats 72 – 75 times per minute.

· The human heart is myogenic in nature. Contraction is initiated by a specialized portion of the heart muscle, the sino-atrial (SA) node which is situated in the wall of the right atrium near the opening of the superior vena cava

· Sino-atrial node acts as the ‘pacemaker’ of the heart because it is capable of initiating impulse which can stimulate the heart muscles to contract.

· The impulse from the sinoatrial node spreads as a wave of contraction over the right and left atrial wall pushing the blood through the atrioventricular valves into the ventricles.

· The wave of contraction from SA node reaches the atrioventricular (AV) node which is stimulated to emit an impulse of contraction spreading to the ventricular muscle via the atrioventricular bundle and the Purkinje fibres.

· Pulse: When the heart beats the blood is forced into the arteries. The expansion of the artery every time the blood is forced into it is called pulse. It can be felt by placing the fingertip on the artery near the wrist. Normal pulse rate ranges from 70 – 90 / min.

Cardiac Cycle

· The sequence of events occurring from the beginning to the completion of one heart beat is called cardiac cycle. During cardiac cycle blood flows through the chambers of the heart in a specific direction. Each cardiac cycle lasts about 0.8 second. The events during a single cardiac cycle involves

· (a) Atrial systole: Contraction of auricles (0.1 sec)

· (b) Ventricular systole: Contraction of ventricles (0.3 sec)

· (c) Ventricular diastole: Relaxation of ventricles (0.4 sec)

Heart Sound

The first sound LUBB is of longer duration and is produced by the closure of the tricuspid and bicuspid valves after the beginning of ventricular systole. The second sound DUPP is of a shorter duration and produced by the closure of semilunar valves at the end of ventricular systole.

Blood pressure

Blood pressure is the force exerted during the flow of blood against the lateral walls of arteries. The blood pressure is high in the arteries gradually drops in the arterioles and capillaries and become very low in the veins.

· In an healthy adult during normal resting condition systolic and diastolic blood pressure is expressed as 120mm / 80mm Hg. Blood pressure varies during conditions of physical exercise, anxiety, emotions, stress and sleep.

· A prolonged or constant elevation of blood pressure is a condition known as hypertension (High blood pressure) can increase the risk of heart attack and stroke. Decrease in blood pressure is termed hypotension (Low blood pressure).

Stethoscope

· A stethoscope is used to detect the sound produced by the internal organs of human body. The heart sound is heard by placing the stethoscope on the chest. It is a useful diagnostic tool to identify and localize health problems and diagnose disease. The modern electronic stethoscopes are high precisioned instruments.

Sphygmomanometer

· Sphygmomanometer is a clinical instrument used to measure blood pressure when a person is in a relaxed and resting condition. The pressure of the brachial artery is measured.

· It helps to estimate the state of blood circulation and the working of the heart. It helps to diagnose conditions such as increased or decreased blood pressure. Monometric and modern digital types are the apparatus used to measure blood pressure.

Blood Groups

· Human blood contains certain specific substances called agglutinogens or antigens (Ag) and agglutinins or antibodies (Ab). Antigens are found on the membrane surface of RBC. Antibodies are present in blood plasma.

· (i) ‘A’ group individuals: Antigen A is present on the surface of RBC and antibody b (anti-b) is present in the plasma.

· (ii) ‘B’ group individuals: Antigen B is present on the surface of RBC and antibody a (anti - a) is present in the plasma.

· (iii) ‘AB’ group individuals: Antigens A and B are present on the surface of RBC and both the antibodies are absent in the plasma.

· (iv) ‘O’ group individuals: Antigen A or B are absent on the surface of RBC. However, the plasma contains both the antibodies a and b (anti a and b).

Blood donation

· Persons with ‘AB’ blood group are called ‘Universal Recipient’ as they can receive blood from persons with any blood group.

· Persons with ‘O’ blood group are called ‘Universal Donor’ as they can donate blood to persons with any blood group.

Rh factor

Rh factor was discovered by Landsteiner and Wiener in 1940 in Rhesus monkey. The surface of RBC contains the antigen for Rh factor. Rh+ ( positive) persons have Rh antigen on the surface of RBC while, Rh– (negative) persons do not have Rh antigen on the surface of RBC. Antibodies developed against this Rh antigen is called Rh antibodies.

Lymphatic System

· The lymphatic system comprises of lymphatic capillaries, lymphatic vessels, lymph nodes and lymphatic ducts. Lymph is the fluid that flows through the lymphatic system.

· The lymphatic capillaries unite to form large lymphatic vessels. Lymph nodes are small oval or pear shaped structures located along the length of lymphatic vessels.

· Lymph from the intercellular spaces drains into lymphatic capillaries. Lymph is a colourless fluid formed when plasma, proteins and blood cells escape into intercellular spaces in the tissues through the pores present in the walls of capillaries.

Functions of Lymph

· Supplies nutrients and oxygen to those parts where blood cannot reach

· It drains away excess tissue fluid and metabolites and returns proteins to the blood from tissue spaces.

· The lymph also carries absorbed fats from small intestine to the blood. The lymphatic capillaries of intestinal villi (lacteals) absorb digested fats.

· Lymphocytes in the lymph defend the body from infections.

CONCEPT MAP