To understand the human body, its organs and the way it works, we need to start with the simple cell. The body is made up of cells, whether in our skin, our bones or inner organs.
A cell is the smallest living independent unit in the body. It can grow and reproduce itself. Some organisms are made up of one cell. Others are made up of more. There are billions upon billions of cells in the human body. Every second a cell dies and is replaced by new cells through the process of cell division.
Each and every cell consists of a cell body and a cell nucleus. The smallest cell in the body is only a few millimetres in size and cannot be seen by the human eye. The largest can grow up to one metre, courtesy of the cell’s ability to spread through protuberance growth. Nerve cells are often the largest cells in the body.
Cell Function Each cell in the body has a specific task:
Bone cells – Support function; e.g. lime salts are stored in the ground substance. Muscle cells – Contraction function; e.g. movement is made possible. White blood cells – Defence function; e.g. their job is to fight invaders, infections and dangerous substances. They consume the invader and eliminate it with a special enzyme. Alternatively anti-bodies can be fired at the invader by the white blood cells. Liver cells – Detoxification function; e.g. toxins are sent to the kidneys so that they can be expelled from the body. Nerve cells – Excitation function; e.g. they produce electrical impulses. Vision cells – Light function; e.g. light is draw in from outside and converted into an electrical impulse. This impulse runs up to the visual cortex in the cerebrum. 2.1 Cell Structure
As explained, a cell consists of a cell body and a cell nucleus. The cell body and nucleus are encircled by a membrane. This is a fluidic barrier to any outside substance unless invited in. Inside the cell nucleus is the nucleoplasma and in the cell body the cytoplasma.
Membrane The membrane is made up of a double layer of lipids. Inside this layer are carrier molecules, whose job it is to act as a kind of gate keeper. They decide who comes in and out of the cell. Carrier molecules can bind themselves to substances, such as an amino acid. But this is only possible if they fit together like a lock and key. To travel in and out of a cell, a form of energy is needed. The cell generates an active transport to achieve this. There is also passive transport, which is achieved through filtration, diffusion and osmosis. Energy expenditure is not needed for passive transport.
Nucleus The nucleus is the central command of the cell, it decides the tasks that must be performed there. It also imprints important genetic information onto each and every chromosome. Every cell nucleus contains the same genetic information about the individual. The blueprint on how to build an individual protein, hormone or enzyme is contained within this code. The code determines what the cell will build, e.g. whether a human, an animal or a plant. This code must be followed without exception to ensure no errors. But of course, errors can and do happen.
Nucleus Components The nucleus consists of the following parts:
Chromosome – These are the carriers of genetic information. In their working form, chromosomes exist as chromatin (an uncondensed version of a chromosome). You can imagine this as a spiralised chromosome. Nucleole – Ribonucleic acid is built and stored in nucleoli. Karyolymph – This is a protein-filled liquid that exists inside the nucleus. The nucleoli and chromosomes make their home here.
Cell Body The role of the cell body is to act as a work and storage area. Hormones and enzymes are created there and sent to the body on demand. To make this happen the cell body requires certain cell organelles. In other words, ‘little organs’.
Mitochrondia – The power station of the cell. Energy is produced here for whatever action is needed. Ribosomes – These contain RNA and their role is to manufacture proteins. Smooth Endoplasmic Reticulum - Is the transport and logistics centre of the cell. Rough Endoplasmic Reticulum – Ribosomes live on the outside of these and therefore are important work horses in the production and transport of protein. Golgi Apparatus – Helps to build secretions, package proteins and transport these in vesicles to the cell membrane so that they can be transported out of the cell. Lysosomes – These are protein-degrading enzymes. They are often found in phagocytes and serve in the breaking down of bacteria and viruses. Centriole – Builds the cylinder-shaped apparatus necessary in cell division. Microtubule – Builds a scaffolding system to form the cell skeleton. They have a special role in the intracellular transport of nerve cells.
Cells build tissue. Tissue is a collection of similar cells from the same origin. They have a specific organisation and a specific task. Sometimes organelles are used to ensure these specifics are fulfilled. There are several different types of tissue:
Epithelial tissue Connective tissue Muscle tissue Nerve tissue
Organs An organ is built out of many different kinds of tissues. It is a unified system with a specific function. Each organ has:
Parenchyma – These are the cells of an organ which are in charge of the organ’s specific work. For example, heart muscle cells needed for heart contraction. Stroma – Is made of connective tissue. It supports the parenchyma and gives it stability and strength. Stroma contains nerves and blood vessels. These nourish the parenchyma.
Organ Systems There are ten organ systems in the body:
Musculoskeletal Digestion Respiratory Circulatory Endocrine Reproductive Lymphatic Skin / Integumentary Nervous Sensory 3.1 Epithelial Tissue
Epithelial tissue is often called Epithelium. It is the outermost layer of tissue whether located inside or outside the body. For example, the skin, or mucous membrane. So that the epithelium can effectively cover the body’s outer layer, it requires a tightly packed cell collective. This means the cells sit tightly side by side, without any fluid between them.
Epithelial tissue does not contain any blood vessels and must be nourished by the underlying connective tissue through the process of diffusion. Both tissues are separated by a basal membrane. The blood vessels rush up to meet this basal membrane. Oxygen and nutrients leave the capillaries and move through the basal membrane to nourish the epithelial cells.
3.2 Connective Tissue
Connective tissue is the most common tissue found in the human body. It is a binding element and binds tissue, organs and organ systems into unique units. On the one hand, it can be used as a layer between organs and on the other hand as part of the inner structure of an organ. It also has a supportive function, which is seen in the construction of cartilage and bones.
3.2.2 Connective Tissue Composition
Connective tissue consists of cells and intercellular substance. The cells consist of stationary and non-stationary cells. The intercellular substance consists of ground substance and fibres. Let’s take a closer look at the types of connective tissue cells.
Stationary cells consist of:
Fibrocytes: a cell that produces fibrous tissue. Fibroblasts: a cell that is the preliminary stage of the fibrocyte. It is responsible for the building of connective tissue. They are specialised in manufacturing connective tissue fibres.
Non-stationary cells consist of:
Defence cells such as Granulocytes, Histiocytes, and Lymphocytes.
Now for a closer look at the intercellular substance. It consists of:
Ground substance: is the liquid or intercellular liquid that makes up each cell. There is a difference between ground substance and intercellular substance. Ground substance can appear in certain organs as not only liquid but also as gel-like or hard. Its gel-like form is found typically in lymphatic organs such as the Spleen, Lymph Nodules and Tonsils. In its hard form it is found in cartilage and bones. Ground substance keeps its solid form courtesy of the store calcium salts found in it. Water is not found in the ground substance of bones. Fibres: There are three types of fibres – reticulin fibres, collagen fibres and elastic fibres.
There are different types of connective tissue:
Reticular connective tissue Fat tissue or adipose (for building and storage) Loose connective tissue Firm connective tissue Cartilage tissue Bone tissue 3.3 Muscle Tissue
There are two types of muscle tissue: smooth and striated. A special note is also heart muscle tissue.
3.3.1 Smooth Muscle Tissue
You can find this type of tissue in the stomach wall, the intestines and the gall bladder. The characteristics of smooth muscle tissue are:
Involuntary: You cannot consciously influence the peristaltic work of the stomach or intestines. This works involuntarily. Slow, rhythmic and autonomous: this means that the contraction command is self-directed. Within the muscular layer of the stomach wall or intestines are nerve cells, which drive the autonomous work. Receptors in a particular area of the digestive tract register the location and presence of undigested food. Nerve fibres send electrical impulses to the surrounding muscle cells to start the process of contraction in order to move the food along. 3.3.2 Striated Muscle Tissue (Skeletal Tissue)
This type of tissue is found in muscles that grow attached to the skeleton. They make it possible for the body to move voluntarily, e.g. lifting your arm. Characteristics of striated muscle tissue are:
Voluntary Fast movement Independent of any rhythm or cycle Contraction impulse stems from the central nervous system 3.4 Nerve Tissue 3.4.1 Nerve tissue is made up of: Nerve cells: they are responsible for impulse transmission, excitation/stimulation, excitation buildup and stimulus processing. Glia cells: they are specialised nerve cells that support, nourish, protect, build and isolate nerve cells.
Nerve cells are so specialised that they do have possess the capacity for cell division. However, glia cells can.
Nerve Cell Composition A nerve cell consist of the main body which is the Soma and the cell extensions such as the Dendrites and Axon.
Soma: this is the body of the nerve cell. Dendrite: these are short and tree-like branched extensions. Dendrites take on incoming electrical impulses and send them to the soma. Some nerve cells have very long dendrites. Axon: can be from one millimetre up to one metre long. Axon transmits electrical impulses away from the soma. At the end of the axon is the synapse which communicates and forwards impulses onto other nerve cells. 3.4.2 Synapse
A synapse is an activation point for transmitting stimulation and excitation:
From the nerve cell to other nerve cells. From the nerve cell to a target organ, such as a muscle or gland.
Synapse Composition A synapse is comprised of:
Synaptic cleft Presynaptic membrane Postsynaptic membrane
Electrical excitation from the soma directed to the end of the nerve prepares the vesicles containing transmitters in the presynaptic membrane to empty or deposit these transmitters into the postsynaptic membrane. This is the fulfilment of an excitation or contraction impulse.
- Heart (Cor, Cardia)
The heart is a hollow muscle that is situated in the breast cavity and has the specific task of pumping blood around the body ensuring every cell is nourished with oxygen and nutrients. The heart lies in the mediastinum between the two lung lobes.
4.1 Heart Layers
The heart muscle is comprised of three layers:
Inner heart skin (Endocardium) Heart muscle (Myocardium) Heart sac (Pericardium) 4.1.1 Heart Cavity
The heart is divided into a left and a right half. The two halves are separated by the septum. Each half is further divided into atria and ventricles. One for each half. Deoxygenated blood flows into the right half after having circulated the body. The right ventricle pumps this blood into the lungs, so that the blood can be reoxygenated. Oxygenated blood is then pumped back into the left half and out into the body. Cells need blood.
- Circulation 5.1 Anatomy and Physiology
Every cell must be hooked up to the circulatory system, so that it can be nourished by oxygen and nutrients. If this doesn’t happen, the cells die. Blood is pumped into the aorta via the left heart half. From here the blood flows into arteries which empty into smaller arterioles, followed by capillaries. On the way back to the heart, the deoxygenated blood flows into venules that combine with larger veins and finally reaches the vena cava (inferior and superior).
5.2 Circulatory Systems
There are several circulatory systems in the body. There is:
Body’s circulatory system Lung’s circulatory system Portal vein system 5.2.1 Body’s Circulatory System
This system begins in the left ventricle. From here blood follows:
Aorta -> Arteries -> Arterioles -> Capillaries (in charge of the exchange of substances) -> Venules -> Veins -> Inferior and Superior Vena Cava -> Right Atrium in the Heart
Veins transport deoxygenated blood back to the heart. Arteries transport oxygenated blood out of the heart. 5.2.2 Lung’s Circulatory System
This system begins in the right ventricle. From here blood follows:
Truncus Pulmonalis -> Lung Arteries -> Lung Arterioles -> Lung Capillaries (situated around the Alveoli. Oxygen is exchanged for Carbon Dioxide) -> Lung Venules -> Four Lung Veins that converge in the Left Ventricle
Lung arteries transport deoxygenated blood into the lungs. Lung veins transport oxygenated blood out of the lungs.
The flowing of blood into and out of the lung’s circulatory system and into and out of the body’s circulatory system is a continuous movement and process. There is no end and no beginning.
5.2.3 Portal Vein System
As we have seen, the blood flows only one time through the capillaries. The task of the capillaries is to forward and transport the blood to organs and other cells in the body. Eventually the blood must travel back to the heart so that it can be reoxygenated. The Portal Vein System is called a ‘Wonder Network’ because it allows the blood to flow through a ‘second’ set of capillaries.
Let’s take the oxygen needs of the bladder. As the blood flows out of the heart and into the body, it moves through the capillaries and finally reaches the bladder, which takes the oxygen and nutrients out of the blood. Then it returns to the heart and lungs.
The blood that flows to the intestines, the stomach, the spleen and pancreas must also pass through a corresponding capillary network that is a part of the specific organ. Once this happens, the blood collects in the capillaries, transfers into the veins, which unite into the portal vein. The portal vein is located in the liver and from here divides itself into small vessels so that it can reach the end destination of the liver’s hepatic sinusoids. It is here that the blood travels through a second capillary system. It returns to the heart by way of the liver veins.
Deoxygenated but nutrient rich blood flows in the Portal Vein System. It is nutrient rich because the stomach and intestines depend on this nourishment. The Portal Vein System is not a true circulatory system. It is rather a go between that is included in the circulatory system.
5.2.4 Vessel Composition and Tasks
The circulatory system is made up of arteries, veins and capillaries. If you would connect these, they would make up a network of approximately 40,000 kilometres. The arteries and veins are differentiated by the flow or direction that the blood flows in, and not by their content.
Arteries are vessels that:
Originate from the heart’s ventricle. Transport blood away from the heart.
Arteries run inside:
the Body’s Circulatory System: oxygen-rich blood. the Lung’s Circulatory System: oxygen-depleted blood. 22.214.171.124 Veins
Veins are also vessels that:
Converge in the atria of the heart. Transport the blood to the heart.
Veins run inside:
the Body’s Circulatory System: oxygen-depleted blood. the Lung’s Circulatory System: oxygen-rich blood.
Arteries and veins are made up of three layers:
Inner Layer (Intima) – comprising Epithelial tissue also called Endothel. Middle Layer (Media) – comprising musculature. Outer Layer (Adventitia, Externa) – comprising connective tissue.
Medium and small sized veins possess valves that stop the back flow of blood. This is the difference between them and arteries.
Capillaries are in charge of the distribution of substances. They are approximately 1 mm long and so large that a blood cell can swim through them. Capillaries are made up of a thin wall out of single layer Endothel, upon which a basal membrane sits. The Endothel cells are stringed together to build an Endothel pipe or tube.
Substance Exchange Substance exchange takes place in the capillaries because the walls of the arteries and arterioles are too thick. It’s not even possible for water molecules to pass through.
It is not the case that the body’s cells in some way attach themselves to the capillaries, rather they find themselves inside the Interstitium, which is filled with liquid. In order for the oxygen and nutrients to pass through the capillaries, they must first overcome a transit route before they can reach the cells. In the meantime the cells are able to release their waste into the interstitial space so that it can be transported away.
When a cell cannot be nourished by the capillaries, then they will die. If this happens and the heart muscle is prevented from receiving blood, it can cause the death of heart muscle cells or a heart attack.
- Blood 6.1 Composition of Blood
When you would like to perform a blood test, then make sure to uncoagulate the blood so that you can determine the two main properties the blood is made up of:
Blood Plasma: This is the unformed part of the blood, the liquid of the blood, the so-called Blood Water, in which blood proteins, electrolytes, nutrients, waste, trace elements, vitamins, hormones, enzymes, oxygen and carbon dioxide are dissolved. Blood Cells: These are the formed part of the blood and consist of – Red Blood Cells (Erythrocytes), White Blood Cells (Leucocytes) and Blood Platelets (Thrombocytes).
Blood Plasma contains Blood Proteins Blood plasma and blood serum are two different things. Don’t mix them up.
Blood Plasma: contains no blood cells only liquid. It does contain Fibrinogen, which is a blood protein in charge of coagulation. Therefore blood plasma can coagulate. Blood Serum: contains no Fibrinogen and can therefore not coagulate.
Composition of Blood Plasma Blood plasma contains the following: 90% water, 7-8% blood proteins (albumins, globulins, fibrinogen), electrolytes (sodium, potassium, magnesium, calcium), nutrients (glucose, amino acids, fatty acids), waste (creatinine, urea, uric acid), trace elements, vitamins, hormones, enzymes, oxygen and carbon dioxide.
The lymphatic system is a term that describes all of the lymphatic tissues. Individually, the following belong to this system:
Lymph Vessels Lymph Nodes Spleen Thymus Lymphatic tonsillar ring (palate, throat, and lingual tonsil) Appendix Intestinal Lymphatic Tissues (Peyer-Plaques, Solitary Follicle)
Task of the Lymph System There are two important tasks that the Lymphatic System undertakes:
Defence against pathogenic agents: This is made possible by Lymphocytes, which belong to the defence cells. A further important role that they have is in the reticulum cells of the reticular connective tissue in certain lymphatic organs. These reticulum cells belong to phagocytes. Transport system: The lymph transports water, protein, fat and cells out of the body. A particularly important role of the lymph vessels is to remove protein particles out of the interstitial space, because they are too big to pass through the blood capillaries.
Nature of the Lymph System Even though the lymphatic system is an important transport system, it isn’t really a circulatory system. Rather it is a kind of branch. The lymph capillaries start out as blind sacks in the interstitial space and change into ever increasing larger lymph vessels, which in the end combine into two lymph stems, that return venal blood back to the heart.
Lymphatic Fluid Lymph fluid is made up of interstitial fluid. It enters the lymph capillaries and flows into lymph vessels. Lymph vessels are then funnelled into the lymph nodes, where the lymph is purified and cleaned. The lymph is finally transported into the blood. The interstitial liquid comes from blood capillaries and is therefore similar to the lymph found in blood plasma.
Blood plasma leaves the blood -> goes to the interstitial space -> this is taken in by the lymph system -> lymph vessels empty into the blood circulatory system -> and so on.
- Digestive Tract
The digestive tract consists of three important tasks:
The digestive tract is like a very long hose or pipe which begins at the mouth and ends at the anus. Inside the digestive tract several digestive glands produce their secretions so that the chemical breaking down of food can take place. These secretions are also identified as enzymes. They work as catalysators, producing chemical reactions that ensure the efficient and effective running of the tract. Enzymes remain unmodified by these processes. The absorption of these smaller chunks into the blood in order to make them nutritionally available The chemical break down of food into smaller chunks The mechanical crushing of food
Composition of the Digestive Tract
Oral cavity Throat (Pharynx) Food pipe (Esophagus) Stomach (Ventriculus) Small intestine (Intestinum tenue) Colon (Intestinum crassum) Digestive Glands
The following of the digestive glands that inhabit the digestive tract:
Pancreas Liver and Gall Bladder Salivary Glands Sublingual Gland Submandibular Gland Parotid Gland
Tasks of the Digestive Tract The digestive tract has the following tasks:
Taste testing Crushing of food Storage of food in the stomach Mixing of food with digestive enzymes by means of segmental movement of the stomach and intestinal wall Transport of food courtesy of peristaltic movement Breaking down of food into smaller chunks Reabsorption of these chunks into the blood Expulsion of undigested or indigestible food stuff
The breaking down of food (protein, carbohydrates and fat) takes place in the mouth, stomach and intestines so that the nutrients can be absorbed into the blood and lymphatic systems. The following nutrients are processed by the following organs:
Carbohydrates -> Mouth and Intestines -> Changed into Glucose Fat -> Intestines -> Changed into Fatty Acids and Glycerine Protein -> Stomach and Intestines -> Changed into Amino Acids 9.2 Pathway of Nutrition in the Body
Nutrition follows the following pathway into the body:
Eating of Food Through digestion food chunks are separated into glucose, amino acids and fatty acids -> Food chunks are absorbed by the intestinal villi into the blood stream -> The blood stream delivers the nutrients to the whole body so that every cell can be nourished.
Glucose, amino and fatty acids step out of the capillaries and step in to the interstitial space. Bodily waste that the cells produce and is expelled from the body via the kidneys as urine follows a completely reversed pathway. Waste steps out of the cells and passes into the capillaries to enter the circulatory system. From here it can be transported to the kidneys, which performs an important filtration process and is finally expelled from the body as urine.
9.3 Carbohydrates, Proteins and Fats
Carbohydrates (Saccharides) Carbohydrates are nitrogen-free organic connections which is a large part of our everyday nutrition. We find carbs in bread for example, and they can manifest in the form of fructose, glucose and lactose. Carbohydrates provide cells with energy. However, if they provide more energy to the cells than what the body requires then the liver will convert the glucose into fat. These are then saved as fatty deposits.
Proteins Protein consists of – just like carbohydrates – out of the following chemical elements: carbon, hydrogen and oxygen. It also contains nitrogen, sulphur, phosphorus and iron.
To be exact proteins are amino acids, they provide the cells with structure and formative substances that the body then converts or uses as protein. Proteins are an important building block in muscle cells. They are also necessary in the manufacture of enzymes, hormones and blood proteins.
Fats Fat sources are either animal or plant-based products. It can also be produced in the liver out of glucose stores. Fat is differentiated by its structure and can be organised into the following:
Fatty acids and glycerine. It is insoluble in water, but soluble in alcohol for instance. Fats serve the body as energy in reserve, which is why they are stored in the body as fatty deposits. Other than that they are important in the construction workers, e.g. in the renal capsules, which protect the kidneys, or as a fatty buffer in the eyeball. When fat must be used as a form of energy, it must first be converted into glucose by the liver.
- Liver, Gall Bladder and Pancreas 10.1 Liver
The liver has an important detoxification function in the body. It also produces bile and is therefore important in the metabolism of fat, protein and carbohydrates.
The liver detoxifies toxins that enter the body through the food we eat and reaches the liver via the portal vein. This is known as the First Pass Effect. Other than that it also detoxifies toxins that are created by the body itself, particularly in the digestive processes. For example, ammonia is a byproduct of breaking down protein in the intestines. This is usually expelled from the body as urine.
Another task of the liver is the assistance in the maintenance of blood sugar levels and body temperature. The liver is also active in storing different substances in the body such as iron, blood, vitamins, fat, glycogen, but also toxic substances. However, the liver prevents these toxic substances from entering the blood stream by saving them in the cells of the liver.
As you can see above, the liver consists of four lobes: right lobe, left lobe, caudate and quadrate lobes. Note that the gall bladder and the bile duct lie behind the liver. The inferior vena cava enters the liver. The liver veins empty their blood into the vena cava, which returns to the heart. The porta hepatis, which is located in the middle of the posterior surface of the liver, merges with the liver artery and portal vein. The bile duct branches off from these.
10.2 Gall Bladder (Bilis, Chole)
The gall consists of the bile duct, gall bladder and bile. The duodenum, which is the first part of the small intestines, leads off into the second part of the small intestines, otherwise known as the jejunum.
Bile is produced in the liver. This liquid is then transported via the bile duct into the duodenum. It is used here to divide fat contents in the duodenum into smaller fat droplets. These droplets are often referred to as micelle. The advantage of this division of fat into micelles is that the fat cells are too large to break down alone. The bile breaks the fat down into micelles. Lipase, or fat enzymes, are responsible for this work.
The pancreas is actually a gland and not an organ. It lies behind the stomach. It has three parts: a head, a body and a tail. The head of the pancreas lies inside the c-form of the duodenum. The pancreas is responsible for:
Production of digestive enzymes Production of hormones
As the pancreas is a gland, it consists of an endo- and exocrine function.
Exocrine function: all exocrine glands consist of an excretory duct. In the case of the pancreas, this excretory duct runs off into the duodenum. Enzymes are released into this duct so that the duodenum can metabolise carbohydrates, fat and proteins. Endocrine function: all endocrine glands are hormonal glands and therefore do not have an excretory duct. The pancreas is responsible for producing the insulin hormone, which lowers the blood sugar level in the body. When this hormone cannot be produced in sufficient quantities, then it can lead to diabetes mellitus. The pancreas also produces glucagon, which raises the blood sugar level. These hormones are produced in the Langerhans Islets.
Production of Digestive Enzymes The pancreas is responsible for the production of the following digestive enzymes:
Fat digestion -> Lipase Carbo digestion -> Alpha-Amylase Protein digestion -> Trypsinogen and Chymotrypsinogen
- Endocrinology 11.1 Hormones (Messengers)
Hormones are the body’s messengers, which make their way into the blood stream via hormonal glands. After leaving the blood, hormones reach their goal and attach themselves to their corresponding receptor. That’s why hormones and receptors fit together like a lock and key. If they don’t fit together, then it is not possible for the hormone to release its ‘message’.
11.2 Hormonal Glands
There are several hormonal glands in the body:
Pituitary gland Hypothalamus Pineal gland Thyroid gland Parathyroid gland Adrenal gland Pancreas Ovaries / Testes
- Urinary System
The task of the urinary system: blood flows through the kidneys in order to keep the blood free of damaging substances and toxins. The kidneys do this by building urine so that damaging substances can be released as waste from the body.
12.1 Composition of the Urinary System 12.1.1 The urinary system consists of: Two kidneys Two renal pelvis’ with calices Two ureters One bladder One urethra
The urethra and ureter are not the same. Don’t mix them up.
Urethritis – is the infection of the urethra Uretritis – is the infection of the ureter
- Reproductive Organs
The reproductive organs have the task of producing new life. Egg and sperm cells belong to these organs. However, these organs, as well as producing sex hormones and secretions, provide the genitals with their ‘frictionless movement’ during sexual intercourse.
13.1 Male Reproductive Organs
The male sexual area is made up of:
Sacral bone Bladder Rectum Seminal vesicle Prostate gland Bulbourethral gland Epididymis Testis Glans penis Pubic bone / Symphyse 13.2 Female Reproductive Organs
The female sexual area is made up of:
Sacral bone Rectum Uterine orifice Vagina Urethra Pubic bone Bladder Uterus Ovaries Fallopian Tubes
- Respiratory System 14.1 Task of the Respiratory System
The task of the respiratory system is to maintain oxygen levels in the blood and to remove carbon dioxide as the blood returns to the heart. Oxygenated blood is transported to the body’s cells, which is needed to produce energy. Imagine the bronchia as a scaffolding system, one that has the task of channelling air into the lungs so that the gas exchange can take place.
14.2 Composition of the Respiratory System Nose Throat (Pharynx) Voicebox (Larynx) Windpipe (Trachea) Bronchia and Bronchiole Aveoli, which are responsible for the gas exchange 14.3 How The Respiratory System Works
Blood is returned to the heart via the right heart half. It is transported via the lung artery into the lungs. The blood is filtered through lung capillaries into the aveoli. The capillaries actually lie directly on the wall of the alveoli. The exchange of carbon dioxide for oxygen takes place. The blood is then pumped out of the lungs via the lung veins into the left heart half. And from here it reenters the circulatory system.
- Nervous System
The nervous system is one of the most important systems in the body, together with the hormone system. The nervous system works using electrical signals which is different to the hormone system which works using chemical signals. The hormone system is also different in that it is responsible for processes that take a long time, such as growth, maturity, reproduction and metabolism. Whereas the nervous system is responsible for processes that take a short time, such as the contraction of a muscle resulting in movement.
15.1 Topographic Division
The nervous system is divided into the following parts:
Central Nervous System Brain Spinal cord Peripheral Nervous System 12 neural nerves 31 spinal cord nerves
The central nervous system is situated in the middle of the body. All of the nerves that stem from the CNS also build the PNS.
Functional Division The nervous system is divided into the following functional categories:
Somatic Nervous System – this regulates the functions that are conscious and voluntary, such as the lifting or movement of a limb. Other than that it is responsible for remaining conscious of external stimuli. Autonomic Nervous System – this regulates the functions that are unconscious and involuntary, such as the movement of the stomach and intestines. This system can be further divided into: the Sympathetic and Parasympathetic Systems. 15.2 Sympathetic and Parasympathetic
The involuntary or autonomic nervous system is often referred to as an inner world system, because it is responsible for important vital functions such as digestion, breathing, circulation and heart beat. This must work without the conscious input of the mind and brain. It also takes care of the intimate cooperative working union between the body’s organs.
Sympathetic System Is responsible for the flight or fight response. It diverts blood away from digestion to the skeleton, muscles and heart in preparation of flight or fight. This allows the blood pressure to increase, the heart to beat faster and the breathing airways to expand. Even the eye is prepared, as the pupils are dilated so that vision can be increased (mydriasis). The sympathetic system springs from the breast and lower back region. That’s why it is often called the thoracolumbar system.
Parasympathetic System Is responsible for returning the body to a state of balance and homeostasis after the flight and fight response. It returns the body to a state of relaxation, calm and saves energy. It slows the heart and breathing. It narrows the heart arteries and bronchia, which reduces blood pressure. It takes the digestive secretions that were increased during flight and fight, and moves them into the digestive canal. This results in the emptying of the bladder and colon. As for the eyes, the pupils are returned to normal (miosis). The parasympathetic system stems from the brain stem and the sacral bone. That’s why it is often called the craniosacral system.