In this essay I will be looking at the human body and how it is organised, from the simple cell to how the body systems co-operate with each other and that everything functions properly. Firstly I will be looking at some simple cells that will group together to make up a tissue. The first cells I will be looking at will be the erythrocytes, the ova cells in women, the spermatozoon cell in men and the epithelial ciliated cells in the throat.
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The erythrocytes are made in the red bone marrow of short bones in the body such as the hip bone, breast bone, ribs etc . Red bone marrow can produce new erythrocytes at the rate of about 1 and half million per second to replace those destroyed . When first formed the erythrocyte has a nucleus, which when the cell matures the nucleus is squeezed out to make way for more haemoglobin to be stored inside the erythrocyte. The erythrocyte is very unique in size and structure; it has the look of a biconcave disk shape. These have inner components that allow the transport of oxygen and help the elimination of carbon dioxide. There are approximately 5 million erythrocytes per mmÂ³ of blood. The redness of the red blood cell comes from the pigment it contains; it contains Haemoglobin which combines with oxygen easily to become oxyhaemoglobin there are 180 million haemoglobin molecules in one erythrocyte. Erythrocytes are about 7.8 micrometres in diameter. Erythrocytes can live up to 120 days inside the body, before they are broken down in the liver and the spleen by a macrophage.
The function of the red blood cell is to primarily transport oxygen from the lungs around the body which can be used for many things, such as making amino acids, lipids and carbohydrates, Their second function is to get rid of carbon dioxide from the tissues to the lungs to be excreted out by the lungs. Oxygen carried by the red blood cells can bind with iron atoms in the blood meaning that haemoglobin can carry 4 oxygen atoms at its maximum capacity. The ability of oxygen to bind with haemoglobin depends on a few factors such as the acidity of the blood and also the temperature. Erythrocytes make up 45% of blood inside the body; the other 55% is plasma.
THE OVA CELLS
The ova cells are produced in the ovaries of women. This is the by-product of the ovaries which is the tissue that makes the ova. The ovum is a smaller version of an ovary which is small enough to pass down the fallopian tube. This cell is visible and does not need a microscope to see it. It measures in diameter 120um. It’s almost a perfect circular cell which has tough follicle cells surrounding the egg to protect it. These cells are normally called ova and they ovulate once every 28 days.
The function of ova cells is so that it gives the spermatozoon a chance to fertilise the egg and it has to contain nutrients and metabolites to help sustain itself in early development to hopefully create a human life, as you may well know it is a cycle where once a month a egg develops in the ovaries and is passed down the fallopian tube where it can be fertilised, if fertilisation happens the inside the ova cell, cell division occurs until it reaches the uterus, if unfertilised it will pass out of the body, but if it is fertilised the weight of the ova will imbed itself into the uterus cell wall where it will grow and develop, a successful fertilisation normally is when the woman uterus cell wall is at its highest which is normally the 14th day since the last ovulation. Its structure is perfect for its function, if it was any other shape it could get stuck in the fallopian tube.
Otherwise known as the sperm cell, this cell is made in the seminiferous tubules in the testes which are lined by germinal epithelial cells which divide repeatedly, forming cells called spermatogonia. The spermatozoon have many structural sections which make it agile and fast. This cell is very specialised and it has some of what most cells have like a head consisting of a nucleus, which contains DNA conjugated with protein in a highly condensed form, mitochondria, microtubules and an acrosome. The nucleus contains the highly condensed set of chromosomes. The condensed state of genetic material reduces the amount of energy needed to transport the sperm. The microtubules produce the whip like movement of a mature sperm, which helps its suspension helping towards the “swim” to the egg. The mitochondria give the sperm cell the energy it needs to swim, and the acrosome is the storage site of enzymes which help the sperm digest the layers surrounding the egg thus being able to penetrate it.
Its primary function is to fertilise an ovum cell, its structure helps it achieve its goal.
THE EPITHELIAL CELLS
Epithelial cells are produced pretty much anywhere needed in the body where something needs to be protected as we have different types of epithelial cells, take for instance we have squamous epithelium which is also known as pavement epithelium which is found in the walls of blood capillaries and alveoli in the lungs, we also have cuboidal epithelium which is found in some kidney tubules, columnar epithelium which is found in the lining of the small intestine, we also have glandular epithelium which is found in the lining of the rectum, we also have ciliated epithelium, this is formed in the windpipe and It’s structure is takes is more of a columnar shape, it has ciliated hairs which beat away from the lungs to move mucus or any other micro-organisms and dust away from the lungs. Smokers are known to have damaged the ciliated hairs by the tar in the cigarettes making the hairs sticky and rigid or they have burnt them. It also has a cytoskeleton called the axoneme, the hairs itself is made of microtubules allowing the hairs to move with more flexibility
Its function is just to keep out any foreign tissue, keep micro-organisms out and keep the lungs dust free, its structure helps it as the cilia hairs are facing away from the lungs meaning it will try and keep it by forcing it upwards.
The epithelial cells will group together to make epithelial tissue which is found in all areas and surfaces of the body, it is specialised to form a covering and or lining of all internal and external surfaces of the body. Epithelial tissue regardless of what type it is, it is separated from a thin-underlying tissue by a thin sheet of connective tissue, the basement membrane, which provides structural support for the epithelium and binds to other neighbouring structures. The ciliated cells in the throat group together to make ciliated epithelial tissue which is formed in a lining normally of the windpipe to help clear mucus, micro-organisms and any foreign tissue a lot more faster and easier than one cell alone. This helps to form one part of the respiratory system.
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Connective tissue is used to support the body and can bind or connect all tissues together. I will talk about one type of connective tissue which is going to be the bones in our body can also be about the bones in our body. The bones primarily give us the support we need and also give us locomotion to move, it protects delicate organs such as the brain from damage, and is also the site for where erythrocytes are made. It also plays a part in homeostasis which controls the amount of calcium in the blood. Under a microscope the bone is arranged in concentrated layers (lamellae) around the small canals called a haversian canal which interconnects to a volkmann’s canal which contains a blood vessel, a lymph and nerve cell.
Muscle tissue allows us to be able to relax or contrast our muscles to for us to exercise movement or do some work which requires us to use our muscles, its structure depends on the muscles that come from different areas of the body. We have smooth muscle tissue, skeletal muscle tissue and cardiac muscle tissue. I will now relate to one example which I will look at the structure and function of the smooth muscle tissue. The structure of smooth muscle tissue is made up of thin elongated muscle cells or fibres, these cells are long and pointed to the end and each cell has a large oval nucleus. The smooth muscle tissue is involuntary and we no control over it, some places you will find this tissue are the walls of the bladder, the uterus and the walls of blood vessels, its function is to control, slow involuntary movements such as the contraction of muscle tissue in the walls of the intestines and stomach.
Nervous tissue is made up of nerve cells, also known as motor neuron which makes up one part of the nervous system. The structure of a motor neurone is pretty complex, these are lay up and down the body almost touching one another, via the dendrites through the axon, to the synapse, to be dissolved in neurotransmitters to another dendrite, and the central nervous system has three components for it to efficiently work, the motor neurone, the spinal cord and the brain. All motor neurones are connected to the spinal cord and the brain is connected to the spinal cord. A motor neurones function is to detect stimuli and respond to it adequately, it does this by sending electrical messages via the motor neurones to the spinal cord, to the brain and from the brain back to the motor neurones to the connected muscle to react to the stimuli. Its structure means the surface area of motor neurone is big enough to send high powered electrical messages at very high speeds.
Up to now we have named a few cells which have developed into tissues, I will now look at the organs from the tissues that come together. The red blood cells have grouped up with plasma to make the blood, the squamous epithelial cells have grouped together to make capillaries, capillaries have grouped and made veins and arteries. All this is has made the circulatory system. The heart is the main organ in this system which too was made of a muscle cell which then grouped to make muscle tissue, making it what it is, the heart is specialised as a muscle as it needs pressure to pump the blood around the body, also it is hallow on the inside which allows the blood to fill the heart and then pump it around the body again. It is made of four chambers, which fill with blood, but they work separately because blood pumped into the heart is deoxygenated and pumped out oxygenated. Together they operate to form the circulatory system.
The systems eventually start working together as one, like the respiratory system works with the circulatory system, the endocrine system works with the whole body giving it hormones, the nervous system works with the brain and spinal cord using nerve cells. The digestive system works alongside the reproductive system. With this in mind we will look at how the body systems work as one entire unit. To ensure we have life, we must to be able to breathe and for that to happen we need our heart beating with blood. The oxygen we breathe in is absorbed into the bloodstream which circulates around our body, picking up glucose and urea from the liver and arriving back at the lungs, and the waste products, like carbon dioxide is excreted. Blood contains waste products such as urea which is given to the liver and bile is added to this ready for digestion in the form of urine but that is after it has passed the kidneys. This links, the circulatory system, the respiratory system and digestive system together. The endocrine system also helps the digestion system by regulating the water balance and blood pressure with the use of very important hormones, such as thyroxin which controls the body’s metabolism. The endocrine system also works with nervous system as it regulates internal functions and maintaining homeostasis. The reproductive system is linked to the digestive system as waste water is excreted through the sexual organs. So the body is linked in many ways to help it function as one whole unit.
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