Chapter Two : Transport

The main concepts of Chapter Two:
Transport in living organisms

1- In primitive plants raw materials and products of photosynthesis move from one cell to another by osmosis, diffusion and active transport.

2- In higher plants gases move by diffusion, mineral salts and soluble products of photosynthesis are transported through vascular tissues "xylem and phloem".

3- Xylem and phloem extend from the root, through the stem to the leaves.

4- Xylem transports water and mineral salts from the root to the leaves as well as it supports the plant.

5- The young dicot stem consists of the following tissues:
- epidermis
- cortex
- vascular cylinder which consists of
1- Pericycle 2- pith
3- Medullary rays 4- vascular bundels
Each vascular bundel consists of phloem - xylem - cambium

6- Stem cortex consists of collenchyma and parenchyma.

7- The Xylem tissue consists of cylindrical elongated cells called vessels and pentagonal or hexagonal tubes called trachieds.

8- Pith are unlignified sites found on the primary cellulose wall.

9- Xylem vessels and tracheids have lignin deposits which take the form of annular - spiral - reticulate and scalari form.

10- There are many different theories which explain the ascent of water in the plant; these theories are:
a- The root pressure theory.
b - Imbibition theory
c- Capillary theory
d- Cohesion - adhesion transpiration pull.

11- Exudation it is the natural phenomenon through which the water comes out if the stem is cut near the soil (root).

12- The embibition theory states that the colloidal nature of cellulose and lignin helps the walls of xylem to imbibe the water, this theory has a limited effect on the ascent of sap.

13- Water rises up through tiny tubes against gravity by capillarity, it has a limited effect on the ascent of sap.

14- Cohesion - adhesion and transpiration pull was explained by Dixon and Joly in 1895 it states that the ascent of water through xylem vessels depends upon three forces, cohesive force which is the strong mutual attraction between water molecules, adhesive force which is the attraction between water molecules and xylem molecules, which holds the water column against gravity; transpiration pull of the leaf which is the continuous process of transpiration in the leaves attracts or pulls the water column upwards.

15- The conditions that are necessary for the ascent of sap in xylem are:
- free of any gas babbles
- capillary tubes
- the wall should be of colloidal nature.

16- The phloem consists of sieve tubes, companion cell, and phloem parenchyma.

17- Cytoplasmic streaming is the circular movement of the cytoplasm inside the sieve tubes and the companion cells. It is affected by the amount of oxygen and the temperature.

18- The process of transport takes place in the human body through two systems which are:
a- The circulatory system.
b - The lymphatic system.

19- The circulatory system in man consists of the heart, the blood vessels and the blood.

20- The heart is a hollow muscular organ, it lies nearly in the middle of the chest cavity, it is enclosed by a pericardium membrane.

21- The heart consist of two thin walled upper chambers called atria and two thick walled lower chambers called ventricles.

22- The tricuspid valve between right atrium and right ventricle is made up of three flaps.

23- The Bicuspid valve (mitral) between left atrium and left ventricle made up of two flaps.

24- Blood vessels consists of:
a- Artries, b- veins, c- capillaries

25- Both artries and veins consists of three layers:
a- outer connective tissue
b - middle unstriated muscle fibers.
c- inner endothelium

26- Artries are more elastic than veins, they pulsate and buried deep in muscles.

27- Veins have internal valves to prevent the back flow of the blood.

28- The human blood is about 5.6 litre, it consists of plasma 54%, red blood cells, white blood cells and platelets.

29- Red blood cells are about 5 millions/mm³. They have the haemoglobin which combines with oxygen and carbon dioxide.

30- White blood cells which are about 7000/ mm³, they protect the body against infections diseases.

31- The red blood cells are produced from the bone marrow (every 120 days.)

32- The white blood cells are produced from the bone marrow and lymphatic nodes.

33- The blood plasma consists mainly of water, inorganic salts, proteins and other components.

34- Blood has many functions:
a- Transports digested food, oxygen, CO₂, nitrogenous compounds, hormones and enzymes.
b - It controls the metabolism process and keeps body temp. at 37 ^oC.
c- It regulates the internal environment.
d- It protects the body against microbes.
e- It stops bleeding by clot formation.

35- The rhythmic heart beats are spontaneous i.e. they originate from the cardiac tissue itself.

36- The sino - atrial node acts are pace - maker, it is joined to two nerves:
a- vagus nerve which slows down heart beats.
b - Sympathetic nerve which accelerates heart beats.

37- The number of heart beats is affected by some factors that it decreases during sleeping and increases during physical effort and in case of Joy.

38- Two sounds in the heart beats are distinguished:
1- long and low pitched due to the closure of the tricuspid and bicuspid valves.
2- Short and high pitched due to the closure of aortic and pulmonary valves.

39- There are three blood circulations:
A- pulmonary circulation which starts from right ventricle and ends at the left atrium.
B - systematic circulation which starts at the left ventricle and ends at the right atrium.
C - Hepatic portal circulation: when glucose and amino acids are absorbed by the villi and pour their contents into the liver cells.

40- The mechanism of blood clot.

41- Blood does not clot inside blood vessels because the liver secretes heparin which prevents the conversion of prothrombin to thrombin.

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