The Circulatory System, Blood and The Lymphatic System

The Circulatory System

• Consists of the heart, a pumping organ.
  Veins carry blood to the heart.
  Arteries carry blood away from the heart.
  Capillaries are narrow tubes that connect arteries and veins.

Functions of the Circulatory System

 

1. To carry digested food from the small intestine to all areas in the body which need it.


2. To carry oxygen from the lungs to the rest of the body.


3. To aid in the disposal of all wastes from the body.


4. To distribute heat.


5. To fight diseases by using white blood cells to fight off infection.

 

• Differences between Arteries and Veins
  

  Arteries and Veins have many differences:

  
  
  Arteries:                carrys blood away from the heart.


• 2.    Have thick muscular walls


• 3.    Have a pulse


• 4.    Deep under the skin


• 5.    Have no valves


• 6.    Arteries branch at their ends, into tiny arterioles those then join capillaries.

• Veins         :


• 1.    - Carry blood to the heart. 


• 2.    Have thin walls


• 3.    Do not have a pulse   


• 4.    Near surface of the skin


• 5.    Have valves to stop back-flow of blood.


•    6.    Veins branch at their beginnings into tiny venules which join capillaries.


• 


• Blood Flow
  Blood enters the right atrium through the venae cavae.
  From the right atrium the blood enters the right ventricle.
  From here it flows to the lungs in the pulmonary artery.
  From the lungs the blood enters the left atrium through the pulmonary vein.
  The blood goes from the left atrium to the left ventricle.
  The left ventricle is the main chamber of the heart and blood is pumped from here to the rest of the body through the main artery called the aorta.

 

• Composition of the Blood
  Blood is made up of 4 different substances:
  1.Plasma – this is the liquid part of the blood and is about 90% water
  2.Red Blood Cells – these contain haemoglobin and carries oxygen around the body.
  3.White Blood Cells – these cells fight infection.
  4.Platelets – these cells are involved in clotting the blood


• Functions of the Blood
  1. Transportation :The blood transports substances around the body.
  2. Immunity : The blood helps our body to fight infection.
  3.The blood forms clots that stops us from losing all our blood if we are cut


• Hepatic Portal System
  The hepatic portal vein carries blood from the intestine to the liver.
  The hepatic vein carries blood from the liver to the heart.


• Functions of the Liver
  1.Regulates the amount of glucose (sugar) in the blood in conjunction with the hormone insulin.
  2.Regulates the level of lipids (fats).
  3.Breaks down excess amino acids to ammonia and then urea.
  4.Produces bile which helps break down fats.
  5.Regulates body temperature.
  6.Stores vitamins and minerals.


• Regulation of Body Temperature
  Animals can keep the body warm by movement, wool, hair, respiration
  Animals can keep the body cool by lying in a shaded area, sweating, rolling in mud (pigs)
  Critical Temperature
  –The upper critical temperature is the point at which an animal needs to use energy to cool down
  –The lower critical temperature is the point where an animal uses energy to keep warm
  Optimum production levels are within the upper and lower range
  Age, weight, feed intake, feed type, building type, insulation and flooring affect critical temperature.


• The Lymphatic System
  The Lymphatic system absorbs fluid that has diffused from blood capillaries. It transports it to larger lymph vessels and eventually empties into the subclavian vein, which brings it to the heart.
  Lymph nodes (found along lymphatic vessels) and bone marrow produce lymphocytes
  –Lymphocytes are types of white blood cells needed for immunity
  –They act as a filter in the lymphatic system removing infectious organisms such as bacteria from lymph.It transports lymph around the body


• Functions:
  –To collect excess tissue fluid and return it to the bloodstream
  –To absorb fats from the intestine and transport them to the bloodstream
  –To defend the body against disease


• .Immunity
  Immunity is the ability of an organism to resist disease through the use of antibodies and white blood cells in response to exposure to the disease.
  
  
  
  • Active Immunity (animal produces its own antibodies – long term)
  
  
  
  –Natural Active Immunity - acquired when the body is infected by bacteria or virus. The body produces antibodies to fight the infection. They provide protection against the disease in the future.
  –Artificial Active Immunity - acquired artificially by means of vaccination.
  
  
  
  • Passive Immunity (animal receives antibodies – short term)
  
  
  
  –Natural Passive Immunity - acquired when antibodies are passed through mother’s milk or across the placenta.
  –Artificial Passive Immunity – acquired when antibodies are injected into the animal.