P4

Cardiovascular system

The cardiovascular system is made up of blood vessels and your heart. The heart pumps oxygen and blood around your body allowing you to survive. It transports carbon dioxide which is a waste product from your body to your lungs. When you breathe out, carbon dioxide is removed from your body.

Three main functions:
Transportation -
The system transports blood to most of the bodies tissues. In the blood there is special nutrients and oxygen which help us develop and breathe. Waste is removed and hormones are transported through the body with the help of the liquid.
Protection -
The cardiovascular system helps to protect the body with the help of the white blood cells. These cells fight pathogens that have entered your body, this is because they could become harmful to your body. Platelets and red blood cells form a scab which seal wounds. The blood carries antibodies that help with immunity. This can include vaccinations that you have already had or something you are fighting off.
Regulation -
If you have any internal conditions, the cardiovascular system helps maintain it. Blood vessels help keep your body temperature right. They do this by controlling the blood flow to the surface of the skin. When the body overheats, blood vessels near the skin open up which allows blood to let go of its heat. If your body suffers from hypothermia your blood vessels open and close to keep blood flowing. This will help the organs keep going. Your blood also helps to keep the pH the same.

Blood:
An average body contains around 4 to 5 litres of blood. It’s made up of red blood cells, white blood cells, platelets and liquid plasma.
Red Blood cells -
These are the most common type of blood cells and they make up around 45% of blood volume.
White Blood cells -
These make up a small percentage of the total number of cells in the bloodstream. They have important functions for the immune system. Inside of the white blood cells there are granular leukocytes and agranular leukocytes.
Granular Leukocytes: The three types of granular leukocytes are neutrophils, eosinophils, and basophils.
Agranular Leukocytes: There are two major types of agranular leukocytes are lymphocytes and monocytes. Lymphocytes include T cells and natural killer cells that fight off viral infections and B cells that produce antibodies against infections by pathogens.

Platelets:
These are small cell fragments that clot up the blood and help the formation of scabs. They form in the red bone marrow. Platelets don’t contain a nucleus and can only survive in the body for up to a week, as the macrophages capture and digest them.
Plasma:
The plasma makes up around 55% of the bloods volume. It’s a mixture of water, proteins and substances that have dissolved. The percentage of water in there, depends on how hydrated you are. Once the substance is dissolved there can be many different things found in the plasma such as; glucose, oxygen, carbon dioxide, nutrients, electrolytes and waste products. The plasma acts a a transportation function for these substances to move around the body.

The Circulatory Pump:
The heart is a four chambered double pump. Both sides act as separate pumps and do different jobs. They’re separated by a muscular wall. This is called the septum of the heart. The right side of the heart receives blood from the systemic veins. It then pumps it to the lungs. The left side of the heart receives blood from the lungs and pumps it through the arteries.
The top two chambers are called atria. The lower two chambers are called the ventricles. These are more muscular than atria as these are the main pumps. Theres a muscular wall in the middle which is the septum dividing the two sides of the heart. Digestive system

There are four stages to digestion: * Ingestion * Digestion * Absorption * Elimination

Ingestion: Saliva helps break down the carbs from the food which has been chewed into small pieces.
Digestion: The food you swallow will stay in your stomach for five hours, it will then get attacked by enzymes to help break it down.
Absorption: The food that has been mushed now passes through the small intestine. The nutrients are then absorbed into the bloodstream.
Elimination: After nine hours, when the waste has all passed into the large intestine, the water is removed. Then the remaining substance is passed out through the anus.

The alimentary canal:
The alimentary canal is a tube that leads from the mouth to the anus. Many glands are linked in with the alimentary canal, and have certain roles to play in digestion. The food is taken into the mouth and mixed in with saliva, it is then chewed with the help of your teeth and tongue. After this, it is rolled into a ball known as a bolus, and then swallowed. This is called mechanical digestion, mostly useful for breaking down the food.

The salivary glands:
Theres three pairs of salivary glands, these pour the saliva into the mouth. It’s a digestive juice which contains enzymes known as salivary amylase. This begins the digestion of carbohydrates and lubricating the mouth and helping bolus formation.

The oesophagus:
The oesophagus transports the food bolus from the back of the mouth to the stomach. It’s in the oesophagus for a few seconds and no enzymes are made here. It’s mainly a transit for food which is moved by muscular contractions known as peristalsis.

The stomach:
This is the widest part of the alimentary canal. It’s tucked just behind the rib cage, and receives food from the mouth by the oesophagus. Food can stay in the stomach for up to three hours, protein remains the longest. During this, the stomach walls roll the food around, it then results in a paste material called chyme.
Gastric glands produce gastric juice which contains gastric protease and hydrochloric acid. It works well with proteins. In babies, another enzyme digests milk, rennin and solidifies it. The pH of the stomach is usually around 1-2, this means it is strongly acidic. The epithelial lining of the stomach contains goblet cells, these produce thick mucus to protect the lining from acid erosion.
After this, it empties the chyme into the duodenum through the pyloric sphincter. This is a thick ring of muscle that contracts and relaxes.

The duodenum:
The small intestine is the next part of the alimentary canal. It has a small diameter, however it is around 6 metres long. The C-shaped part is the shortest and is called the duodenum. It is mainly to do with digestion and is helped by two large glands called the liver and the pancreas. Juice is poured into this area. The duodenal wall also contains glands which help enzyme juices continue to digest on the proteins, carbohydrates and lipids or fats. They can work on the surface or inside the epithelial lining cells.

The ileum:
The leftovers of the small intestine is mainly to do with the absorption of the fully digested food. It is especially adapted to this as it has a long length, folded interior and a lining covered in thousands of tiny projections called villi. It also has epithelial cells of villi covered in microvilli projections which are very small. This means they can only be detected using an electron microscope.

The colon:
The small intestine meets the large intestine in the right hand corner of the abdomen. there are two remaining remnants now; the caecum and the appendix. They are known as this as they have no function. The appendix could become inflamed and could be a threat to you. A case of this could be called appendicitis. The large intestine consists of the colon and rectum. The colon runs up the right side of the abdomen, then travels across to the left side, then finally ending up in the anus. There are no enzymic juices in the large intestine.
During the journey down the alimentary canal, the glands have poured watery juices onto the chyme. The body can’t lose much water, and the purpose of the large intestine is to slow the passage of the food waste down. This means that the food waste is all that is left as the nutrients have been absorbed. Water can be re-absorbed and the motion becomes solid. It is then eliminated by muscular action of the rectum and relaxation of the anus.
Faeces contain: * cellulose from plant cell walls from fruit and vegetables. * dead bacteria * scraped-off cells from the gut lining
Faeces is a brown colour due to bile pigments.

The liver:
The liver is a large, dark-red organ at the top right half of the abdomen. It partly overlaps the stomach. The liver has many functions that are very important, one of them is to produce bile. Bile flows down the the bile duct into the duodenum. Bile contains no enzymes but it provides important salts that cause the emulsification of fats in the duodenum. This results in the fats forming millions of tiny globules. Bile also contains bile pigments. These are the waste products of degraded haemoglobin from old or broken red blood cells. It is stored in a sac called the gall bladder. The liver releases glucose and other sugars from the blood coming from the small intestine and converts them into glycogen for storage.

The pancreas:
The pancreas is a slim, leaf shaped gland. You can find it in between the intestines and the stomach, near to the duodenum. Pancreatic enzymes go to work with the macronutrients and are important agents for the breakdown of complex food molecules into amino acids