SIMPLE ANATOMY AND PHYSIOLOGY FOR BEGINNERS

I decided to begin this page on simple anatomy and physiology after coming across an article stating that half of Britons are clueless they don't even know where their heart is. Hopefully this will enlighten a few people obviously anatomy and physiology is a very complex subject and it takes years to get a good understanding of it but hopefully at least this page will give some knowledge to the placement of organs and how our bodies work.

PLACEMENT OF MAJOR ORGANS

Placement of the major organs and structures following on from the last two articles on here.

DIGESTIVE SYSTEM

Starting with the mouth and keeping this relatively simple.

Beginning with the teeth a full grown adult has 32 teeth, though some people are born without the 4 third molars commonly known as wisdom teeth, they usually erupt around ages 14/15. We also have 20 milk teeth (our first deciduous teeth) which we begin to lose around ages 5 to 6 and are gradually replaced by our permanent teeth.

Diagram of the mouth, digestion begins within the mouth where food is chewed (masticated) and the action of salivary amylase and pytalin (enzymes that break down carbohydrates)

Tonsils are part of our immune system (lymphoid tissue) to help protect us from infection. The tongue as well has helping us to speak aids digestion by helping us move and chew food and is divided up into areas that help us detect flavours such as sweet, salty, sour and bitter.

Digestion as I mentioned previously begins in the mouth, food is chewed up assisted by the teeth and tongue and mixed with saliva. Saliva helps moisten the food and helps us swallow it, but the enzymes within Saliva, amylase and pytalin break down carbohydrates, which are complex sugars into disaccharides.  This chewed up food is now known as a bolus and is pushed down the oesophagus by the tongue. The oesophagus is a hollow muscular tube commonly known as the gullet. that leads to the stomach. The stomach is a muscular hollow organ that produces hydrochloric acid, to help break down food further and kill bacteria, it also produces Pepsin an enzyme to break down proteins. The stomach's muscular action churns up the food and it is now known as chyme as it passes into the first stage of the small intestine, the Duodenum, it is in the small intestine where the vast majority of digestion takes place.

The accessory digestive organs the pancreas and the liver now assist the process of digestion. The liver produces Bile, this is released and stored in the gallbladder and it is from there it is released into the duodenum its function is to emulsify fats and acts as a deodourant and gives faeces their brown colour. At the same time the pancreas producesdigestive enzymes to further break down carbohydrates into simple sugars monosaccharides (amylase, lactase, sucrase) and (trypsin and chymotrypsin) break down proteins into polypeptides. Lipase breaks the fats down into fatty acids. 

As the broken down food continues along the small intestine the lining is covered in small projections known as Villi, these increase the absorbent area and the nutrients from the food are absorbed through those into the blood stream. Obviously its a lot more complex than this as I'm trying to keep this simple. 

The main function of the large intestine is to absorb water from the faeces and any remaining nutrients and the end result faeces is stored in the rectum until voided.

The Liver does have a very important role in the body besides manufacturing Bile as does the Pancreas and that will be explained in another blog.

URINARY SYSTEM

The Urinary system's function consists of two kidneys two ureters leading down to the bladder and the urethra leading to the external body. The function of the kidneys is to filter the blood through tiny specialised structures known as nephrons. These are very delicate structures than can be damaged through continuous high blood pressure. The kidneys regulate electrolytes (salts) within the body and remove waste such as urea, they also help regulate blood pressure. They excrete this waste as urine. Incidentally urine is sterile until it leaves the body when bacteria acts upon it. The urine then passes down the ureters to the bladder where it is stored until its convent to be emptied. They are placed at the rear of the abdominal cavity and are protected by an area of fat just below the waist.

RESPIRATORY SYSTEM

Since I am keeping this simple I won't go into much detail of how it is an area of our brain that controls respiration but it is suffice to know that when the diaphragm contracts (it is a large muscle that separates our chest from our abdomen) it increases the volume in our chest cavity. At the same time the little intercostal muscles between our ribs contract and lift up the rib cage. Because the air pressures are different and due to various natural scientific laws this draws in more air into our lungs and due to certain receptor nerve cells they send a signal back to our brain instigating the opposite, diaphragm relaxes and we breathe out carbon dioxide. It is the Alveoli (see diagram above) where the interchange of gases takes place into and out of the blood stream for surrounding these tiny little balloon structures are tiny blood vessels known as capillaries, these are merely one cell thick to facilitate the body's waste carbon dioxide to pass into the alveoli and the oxygen in the air in the alveoli to pass into the blood stream.

This happens continuously throughout our lives automatically the average healthy adult 12 to 18 respirations per minute. It's important to remember that each system of the body is dependent on the others to function as they all interact with one another eg. The brain stem controls respiration and respiration is vital to bring oxygen to the body's cells and remove waste and its specialised nerve receptor cells within the aorta that lets the brain know when to evoke inhalation.

You can also see in the diagram the left lung is slightly smaller than the right this is to allow for the heart. As we breathe in through our nose the air is moistened and the whole of the respiratory tract is covered in little hairs 'Cilia' these trap debris and help waft up mucus from the lungs. The Uvula is a fleshy piece of tissue that stops food going into our Trachea (wind pipe) and the trachea leads to the Bronchus which divides into two Bronchi eventually getting smaller and smaller to becoming Bronchioles to which are attached the Alveoli.

Incidentally smoking paralyses these little Cilia rendering them unable to function and they are not able to move the mucous up out of the lungs, this is what leads to the classic smokers' cough.

THE CIRCULATORY SYSTEM PART ONE SHOWING THE HUMAN HEART AND DIRECTION OF BLOOD FLOW THROUGHOUT THE BODY AND INTER RELATIONSHIP OF THE LYMPHATIC SYSTEM

DIAGRAM OF THE HUMAN HEART

The flow chart below shows how blood flows through the heart and around the body

FLOW CHART SHOWING THE CIRCULATORY SYSTEM AND THE RELATIONSHIP TO THE LYMPHATIC SYSTEM

Lungs

Heart

Left Atrium

Left Ventricle

Aorta

Around the body

Arteries

Arterioles

Capillaries

Exchange of blood gasses and nutrients

via interstial fluid at tissue level 

Lymphatic fluid i.e. fluid not picked up
via the capillaries in the circulatory system is picked up
via lymphatic vessels and

Filtered via lymph nodes throughout the body

 makes it way towards

the heart via the lymphatic system

which is separate from the circulatory system

Lymph reaches the major ducts

Capillaries

Venules

Veins

Filtered lymph drains into the Vena Cava via
the Sub Clavian veins and so back into the 
general circulation

Vena Cava

Right Atrium

Right Ventricle

Pulmonary Artery

Pulmonary Arterioles

Pulmonary Capillaries

surrounding Alveoli

Gasseous exchange takes place

oxygenated blood goes back to heart via Pulmonary Veins

to Left Artrium and whole cycle begins again

RED DENOTES OXYGENATED BLOOD

BLUE DENOTES DEOXYGENATED BLOOD

YELLOW DENOTES LYMPHATIC FLUID

PURPLE DENOTES THE INTERCHANGE OF GASSES OXYGEN AND NUTRIENTS AND CARBON DIOXIDE AND WASTE

BLOOD

Blood is divided into two parts cells 45% and plasma 55% although mostly water it carries nutrients, such as minerals, proteins, glucose, hormones and oxygen and carbon dioxide around the body. The three main type of cells are erythrocytes (red blood cells) leucocytes (white blood cells) and platelets (thrombocytes) The red blood cells main function is to carry oxygen to the body's cells, these contain haemoglobin (which contains iron) that helps these cells bind to the oxygen molecules to carry it around the body. White blood cells function is mainly defending the body from infection and platelets are tiny little fragile cells that when damaged as in an injury release substances to cause the blood to clot thus stemming the flow of blood.

There are 4 main groups A, B, AB and O and these can be either Rh positive or Rh negative so blood can be one of 8 types

The ABO system

Blood groups are defined by the ABO system.

• Blood group A has A antigens on its red blood cells and anti-B antibodies in its plasma.
• Blood group B has B antigens and anti-A antibodies in its plasma.
• Blood group O has no antigens but both anti-A and anti-B antibodies. This means that group O red cells can safely be given to anyone. It is the most common blood group in the UK.
• Group AB has both A and B antigens but no antibodies, otherwise it would destroy itself.

Receiving blood from the wrong ABO group could be life-threatening because antibodies in a person with group A blood will attack group B antigens and vice-versa.

The Rh system

Red blood cells sometimes have another antigen, a protein known as the RhD antigen. If this is present, your blood group is RhD positive. If it is absent, you are RhD negative. This means that you can be one of eight blood groups:

• A RhD positive (A+)
• A RhD negative (A-)
• B RhD positive (B+)
• B RhD negative (B-)
• O RhD positive (O+)
• O RhD negative (O-)
• AB RhD positive (AB+)
• AB RhD negative (AB-)

Around 85% of the UK population is RhD positive.

96% of us rely on the other 4% to give blood. Please don't leave it to someone else.

DO SOMETHING AMAZING TODAY GIVE BLOOD

Register as a blood donor
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ENDOCRINE SYSTEM PART ONE

DIAGRAM OF THE ENDOCRINE GLANDS

It is often said that it is the Pituitary Gland that controls the Endocrine system however this is not strictly true although it plays a big part in it. It is the area of the brain known as the Hypothalamus that maintains homeostasis (balance) within the body and one of its functions is to regulate the pituitary gland. You can see from the diagram above the Endocrine system organs which are known as ductless glands meaning their hormones (chemical messengers) are excreted directly into the blood and not through a duct. 

As the Hypothalamus is trying to maintain balance within the body it is constantly check our blood analysing what's needed to help it function at its best so if it detects a fall in certain hormones it will send a message to the pituitary gland say and that pituitary gland will send a hormone to its target organ for example Thyroid Stimulating Hormone that is then excreted into the blood stream to target the Thyroid gland to produce Thyroxine, the Hypothalamus will be constantly checking levels of Thyroxine in the blood and when the levels are correct, it will send a message to the pituitary gland to stop secreting Thyroid Stimulating Hormone and if the levels drop again the same thing happens all over again. This is known as a 'Feedback System' and that is basically how our hormone levels are maintained.

Obviously the subject matter of the Endocrine system is vast and I am only giving the basics and keeping it simple but one thing that affects us all is stress and the endocrine system really is worked.

CORTISOL OFTEN KNOWN AS THE 'STRESS HORMONE' 

Cortisol is a steroid hormone produced within the adrenal cortex in the adrenal glands, these are cone shaped organs sitting on top of the kidneys. It's a very important hormone and responsible for proper glucose metabolism, helping regulate blood pressure, has a part to play in insulin and blood sugar levels and is part of the inflammatory response. It's often known as the stress hormone but as you can see that's only part of its functions, and this is because it's secreted in higher levels as part of the 'Fight or Flight response'. When secreted in short bursts its beneficial to the body as due to it's actions, it helps mobilise energy reserves, heightens memory and lowers response to pain. This is how and why it's beneficial in the 'Fight and Flight response', it acts quickly and helps survival, however today's stresses are not the same as yesteryear and therein lies the problem.

When there is prolonged secretion of this hormone, when stress is on going, it causes blood sugar imbalances, affects bone density, causing it to decrease and also causes a decrease in muscle tissue. It raises blood pressure affects the body's immune system making us more susceptible to infection and leads to poor healing. It also causes shifts in body fat by increasing more fat around the abdominal areas and leads to higher levels of cholesterol.

The Hypothalamus & the Relationship to the Endocrine System in ‘Stress’

Below the flow chart illustrates how our minds' emotions and feelings trigger a reaction in the Hypothalamus to instigate what happens in the 'Fight or Flight' response. The Hypothalamus then in turn influences both the Autonomic Nervous System and the Endocrine system. This is fine short term it helps us cope in dangerous scenarios and was designed as a protective response, however the stresses of today are not those of yesteryear. No harm comes to our bodies in the short term, this is not the case in long term stress. All is not lost for there are ways we can influence the Hypothalamus to prevent the long term damaging effects of stress on our health. I shall be exploring this under Holistic Therapies.