Here is the ninth lesson following on from An Elementary Herbal Course – Lesson 8 – Anatomy and Physiology Pt 1
ANATOMY AND PHYSIOLOGY Pt 2 Continued from Pt 1
THE THORAX.
The THORAX is a cage of bones. It is cone-shaped and is formed by the twelve pairs of ribs so joined in the front to theSTERNUM or BREAST-BONE. Out of the twelve pairs of ribs so joined to form the thorax, only the upper ten pairs are actually joined to the STERNUM. The lower two are not joined to it, and as such are called FLOATING RIBS. Even the ten pairs of ribs that are joined to the sternum are not done so direct, but they are united to the sternum by means of a certain kind of bone called CARTILAGE.
CARTILAGE is a hard flexible substance and as such helps to absorb shock. Nature has provided cartilage in various parts of the body, in order to absorb shocks wherever they may be felt, as a result of accident, etc..
Besides being found in the thorax, as explained above, we also find cartilage used as pads between the vertebra. At the end of the long bones, there has been provided cartilage in order to enable the joint to move easily and without friction. In fact, our external ear is a piece of cartilage covered only by thin muscle and skin.
The use of the thorax is, as already explained, to protect the vital organs enclosed wiyhin it. If the bony cage were absent, a man might instantaneously die should he receive a blow in the chest as that would immediately injure the heart and the lungs, whereas, as he has been provided with the bony cage, the bones will absorb the major portion of the shock, thus keeping the heart and lungs free from danger. As you go on reading this subject, anatomy and physiology, you will begin to realise how wonderful and orderly is the arrangement of creation and how every minor detail is accurately thought out and provided for.
The spaces between the ribs are called INTERCOSTAL SPACES and are covered with muscles called the INTERCOSTAL MUSCLES. Through the upper opening of the thorax passes the windpipe, the food pipe and various blood vessels and nerves. The lower opening of the thorax is closed by a muscle which is arch-shaped, and which is called the DIAPHRAGM, and as you know already, this seperates the thorax from the abdomen.
THE UPPER EXTREMITIES AND HANDS.
There are two identical upper extremities each on either side, and each of which consists of the shoulder, the upper arm, the elbow, the lower arm, the wrist and the hand. We have the following bones within it. The collar bone is called the CLAVICLE. The shoulder blade is called the SCAPULA. The bone of the upper arm is called the HUMERUS. In the fore arm, there are two bones called the RADIUS and ULNA. In the wrist we have eight bones called the CARPELS. In the palm of the hand, we have the five METACARPELS. The PHALANGES are the bones of the fingers, three in each finger except the thumb in which there are only two.
The SCAPULA is a triangular bone, flat and lying in the back area of the ribs. At the upper end andouter angle of the scapula is a cavity called the GLENOID CAVITY into which is fitted the round, ball-like, upper end of the humerus. This we call the shoulder joint. The humerus is a long bone consisting of an upper end, a shaft and a lower end. Its upper end is joined to the glenoid cavity, as already stated, and the lower end is joined to the fore-arm, where it forms the elbow.
In the fore-arm we have two bones, the RADIUS and the ULNA. The RADIUS is on the outer side of the fore-arm, and the ULNA is on the inner side. The upper end of these bones are joined to the Humerus forming a large joint and here it forms a projection, viz. The prominence of the elbow. In the position of the arm, when the palm faces forward and the thumb is turned outwards, the radius and alna will be parallel to each other. If the hand is turned outwards the radius and ulna, rotate upon each other, that is one crosses over the other. This is the position when the thumb is turned inwards. The CARPELS, or the wrist bones are eight in number and they are arranged in two rows. As the wrist is composed of small bones held in position by ligaments, it is flexible and capable of a wide range of movement.
THE LOWER EXTREMITIES AND THE FEET.
The bones of the legs are made more or less on the same plan as the hand. The hip bones, or the PELVIS, are placed like a basin supported on two legs, and in their turn, they support the organs of the abdomen. The thigh bone is called theFEMUR and it is the largest bone in the human body. The TIBIA and FIBULA are the two lower leg bones, the tibia being the larger and inner bone. The knee-cap is called the PATELLA and it is in front of the knee-joint and connected to the tibia. The lower end of the tibia is joined with the ankle bone and here it forms the inner prominence of the ankle. The fibula is a thin long bone placed to the outside of the tibia.
Unlike the bones of the fore-arm, these cannot rotate and cross each other but are fixed. The ankle bones are called the TARSUS, seven in number. One of these is a thick bone, which is called the ASTRAGALUS. Another projects backward forming the projection of the heel, and is called the OSCALCIS. The remaining five tarsal bones form a part of the instep. The METATARSUL bones are five in number to which are joined the PHALLANGES of the toes, an equal number as found in the figers of the hands.
THE JOINTS.
From the foregoing, you have learnt that where two bones meet a joint is formed. Broadly speaking, joints can be divided into two kinds, viz. Fixed joints, in which there is no movement, such as the joints in the CRANIUM, and moveable joints, which allow movement. The latter may be divided into FOUR groups, viz.-
HINGE JOINT. In which movement is obtained forwards and backwards, exactly like a door swung on its hinges. As examples, may be quoted, the elbows, the kness, etc..
BALL and SOCKET JOINTS. In these the round ends of long bones are fitted into a cup shaped socket, of another bone, and these allow great freedom of movement. Examples, the hips and the shoulders.
PIVOT JOINTS. One bone forms a pivot round which the other bone rotates. This joint occurs where the axis or first vertebra is joined to the atlas. Here, this allows the head to move sideways.
GLIDING JOINTS. Here there is only a slight gliding movement, the wrist joints and the joints between any two vertebrae being examples of gliding joints.
LIGAMENTS AND TENDONS.
These are bands of fibrous tissue, white in colour. As they are somewhat elastic, they are capable of expanding and contracting to allow movement to bones and muscles. LIGAMENTS are bands which unite one bone to another, whereas the TENDONS are those that unite the muscles to the bomes.
THE MUSCLES.
Muscles consist of fibres arranged side by side and bound together by a membrane. They are responsible for bringing about the various movements in the body. Muscles contain about seventy-five per cent water and some soluble substances like albumin and a carbohydrate called glycogen. There are also mineral salts, mainly the chlorides and phosphates of sodium and potassium.
Living muscles are clear, red, soft and elastic. It is alkaline in reaction and if it is squeezed a substance called MUSCLE PLASMA, which is thick and semi-fluid, will be obtained. The dead muscle is rigid and non-elastic and is acid in reaction. This condition is called RIGOR MORTIS or death stiffening. When the muscles in the dead body begin to putrify, the muscles once more become loose and then it is considered that the rigor is over.
Muscles may be divided into three kinds and these are, the VOLUNTARY, the INVOLUNTARY and the CARDIAC. A VOLUNTARY muscle has two ends. The POINT OF ORIGIN of the muscle is the point at which it is attached to the fixed bone. The point of attachment to moveable bone is called the POINT OF INSERTION. The thich fleshy part of the muscle between the two ends is called the BELLY of the muscle. The voluntary muscles have the power of contracting at the will of the individual and they are attached to the bones by means of tendons, which are strong, white, non-elastic bands.
INVOLENTARY MUSCLES are so called because these cannot be contracted at will.
This is because, while the voluntary musclesare controlled by the spinal nerves, the involuntary muscles are controlled by the sympathetic nervous system. Their action is a slow rhythmic action and generally shows wave-like movements. These are found mainly distributed in the walls of the blood vessels, trachea, alimentary canal, bladder, etc..
The CARDIAC muscle resembles the voluntary muscles in its being faintly striated, but in its having slow rhythmic movements, controlled by the sympathetic nervous system, it resembles the involuntary muscle.
CHEMICAL CHANGES.
When at rest a muscle takes in oxygen from the blood and lets off carbon dioxide. When it is active this exchange of gas is greatly enhanced. During muscular exertion the complex substances of which the muscles are composed is broken down into singular substances and for this oxygen is used. This oxidation releases energy in the form of heat and thus a muscle when at work, constantly releases energy. Some waste products are released at the same time, mainly carbob dioxide.