Monday, January 14, 2008

Circulation in Animals

What truly is the point of Circulation? Why build such a complex system stretching through out the entire body? Below these questions shall be answered.

Exchange of Materials
The true point of the Circulatory system is to exchange, and transport materials from cells, and to cell, and to other parts of the body. This includes:
  • Oxygen
  • nutrients
  • Sugars, proteins, etc.
  • Water
  • Protective Agents(White blood cells, antibodies, platelet's, etc.)
  • Hormones
  • Carbon Dioxide
  • Urea
  • Water
Multicellular Animals need these essential materials, and to get ride of waste, but unlike unicellular organisms cant obtain it through diffusion alone, for this reason they need the Circulatory system, this network or highway for transport.
Types of Circulatory Systems
All Animals have some characteristics in common for their mode of circulation. The all contain blood vessels, a heart, and some type of fluid to transport materials in (blood for humans).
  • Invertebrates( insects, mollusk, anthropods) contain an open circulatory system which means they have no separation between blood, and interstitial fluid, instead they have hemolymph. This is a fluid that runs through their entire body touching the organs, and giving them nutrients.
  • Invertebrates( Octopie, earthworms, squid ) have separate blood from interstitial fluid. They have at least one heart, complex blood vessels, exchanging of materials between the blood, and the outside interstitial fluid.
  • Vertebrates( humans, clownfish , macaques ) also have a closed circulatory system. They have seperate blood from interstitial fluid, and complex blood vessels. The characteristics of vertebrates differ greatly through different evolutionary stages.
Evolution of heart chambers
The number of heart chambers differs greatly ranging from 2-4 in vertebrates. Having more chambers was a selective value because it is more efficient system, separating oxygen rich, and oxygen poor blood giving cells a fresh supply of concentrated oxygen. Having only 2 chambers, like a fish mixes the oxygen rich, and oxygen poor blood giving less overall oxygen to the cells. Since mammals, and birds are endothermic they also had a selective force to heave 4 chambered hearts so they could supply they needs of making heat by getting the supplies around faster, and with what is truely needed.

Blood Vessels
There are 3 main types of Blood Vessels found in the circulatory system of vertebrates.
  • Arteries are the blood vessels that carry blood away from the heart.
  • They are thicker than veins so that they can be able to make high pressure pumping of blood. Since it is pumping blood to the body it ne eds pressure to force the blood to move to the different parts of the body.
  • Has a narrow diameter to help keep high pressure within the vessels.
  • Veins are the blood vessels that carry blood towards, or back to the heart.
  • Low pressure so that skeletal muscle contractions are able to move the blood flow more easily towards the heart.
  • Wider diameter so there is less pressure.
  • Thinner walls for less pressure.
  • Valves in some of the larger veins help to direct blood flow by opening and closing leading blood to the heart.
  • Very small blood vessels that branch from the larger veins, and arteries but connected to the arterioles, and venules.
  • Very thin, only one layer of cells, endothelium.
  • Very permeable from thinness allowing the diffusions of molecules such as oxygen, and urea, and making for the connection for the transp ort of materials between cells, and the circulatory system.
The blood flow in capillaries can be controlled through the pre-capillary sphincters. They can retrict or allow blood flow through capillaries by either closing, or opening up. This is useful for when certain body parts are in need of blood, open, an d to close them when the part is in no need of blood.
The capillaries also exchange fluids, and solutes into the interstitial fluid through "bulk flow" or having a high pressure gradient. The interstitial fluid also flows into the capillaries through osmosis.
Lymphatic System
The Lymph system very much like the circulatory system and is parallel with it. The Lymph system is an open system, and helps collect, and return interstitial fluid to the blood. It also helps the bodies immune system greatly. It aids in the production of lymphocytes, and anti-bodies, also transporting these throughout the whole body as well as white blood cells to aid wherever they are needed. The system drops its load into the circulatory system near the vena cava, and right atrium.
Mammalian heart
The heart of your typical mammal is very similar, as we saw in the cow heart dissection. It consists of Pulmonary arteries, and veins which pump blood to and out the capillaries of the lungs, and the Aorta which is an artery that pumps blood throughout the body. The Coronary arteries give a supply of blood to the heart giving fresh supplies of oxygen. Many times this is blocked by buildup of cholesterol, and can cause a heart attack which can lead to needing bypass surgery, in which a alternate pathway from the aorta is made to the heart so it can get its supply of blood and not fail to pump.
The heart is made of up 4 chambers, the left and right Ventricle, and the left and right Atrium. These chambers are separated by four valves, made up of connective tissue that prevent back flow keeping the blood pumping in the direction it is needed. The sounds "Lub" and "dub" are produced from these valves closing, and opening. The Atrioventricular valves (AV) are between the atrium, and ventricle, and prevents blood from flowing in the atria when the ventricles contract. The Semi lunar valves are between the ventricles, and arteries and prevent blood from flowing into the ventricles from the arteries when the heart is relaxing.
A Cardiac cycle is one complete cycle of the hear pumping. This is when the heart contracts, and pumps, then relaxes and refills with blood. The contraction phase is called systole, and the relaxation phase is called diastole. This is the way someones blood pressure is measured to check if they have hypertension. The top number is systolic pumping(a higher number), and the bottom number is the diastolic pumping(lower number).

Jan. 10

Here are some key points we should have absorbed today

Animals get thier food by
Filter (suspension) feeding
-Substrate feeding
-Fluid feeding
-Bulk feeding

-Animals cannot make: elements; N, P, K, Fe, Na, Ca and NAD, FAD so they must take it in through food

peristalsis-push food along by rhythmic waves of smooth muscle contraction in walls of the digestive system.

Sphincters-muscular ring-like valves, regulate the passage of material between sections of digestive system.

Accessory glands- salivary glands, pancreas, liver, and gall bladder secrete digestive juices such as enzymes and fluid.

Stomach-stores foos, disinfects food, performs chemical digestion

Ulcers-caused by a bacteria overload in your stomach called helicobacter pylori cured with antibiotics.

Small intestine-chemical digestion, absorption through lining
-duodenum=most digestion
-jejunum=absorption of nutrients and water
-ileum=absorption of nutrients and water

-the small intestine is lined with villi and microvilli
the villi increase the surface area to absorb materials into the blood

large iontestine-re-absorb water
the large intestine is inhabited by countless bacteria including E. coli
the bacteria produce necessary vitamins for survival and help with digestion

Rectum-eliminate feces (extracellular waste) this waste has never been absorbed into the bloodstream.

Tuesday, January 8, 2008

Digestion continued...

The liver is responsible for the production of bile. Bile is a chemical made from dead red blood cells. Bile breaks down the fats that we eat.
After bile is produced it is stored in the gall bladder, it is released in the presence of fats
in order to break them down.


The pancreas breaks down carbohydrates and further breaks down proteins. The peptidases that are made by the pancreas are called

Trypsin, Chymotrypsin, and carboxypeptidase.these are then changes to their inactive form which are trypsinogen,chimotrypsin, and procarboxypeptidase. This change occurs in order to protect the pancreas from getting digested. When needed tripsinogen is changed back into tripsen by the small intestine then tripsen activates the other enzymes to change.

The small intestine is the major organ of digestion and absorption.

The small intestine is over 6m and has a alot of surface area for absorption due to the thousands of villi against its lining.

The small intestine is made of 3 parts the Duodenum where most digestion occurs.

Jejunam and Ileum where absorption of nutrients and water occur.

The nutrients from the food are absorbed through the capillary walls which are only one cell thick

What ever the body cannot put to use gets sent to the large intestine. Products such as cellulose which or body cannot digest is sent here. The large intestine has a bunch of good bacteria

that prduce vitimans and help digest cellulose.

The liver also re-absorbs water back into the blood stream so we dont dehydrate.

The last section of the large intestine is the rectum which eliminates the pheces and undigested materials from the body

and lastly you end up with...


Chemical digestion occurs once food has

entered the stomach from the esophagus.

Most people believe that the stomach's function is digestion. The true function of the stomach is to store food, the stomach makes it possible for us to eat meals through out the day. The stomach also disinfect anything that is not suppose to come down with the food. HCl make the disinfection possible, with a ph of 2 it kills bacteria and begins to break apart food.

The enzyme that digests protein is called pepsin

Luckily we have mucus that is secreted to protect

our stomach lining. If we didn't then the pepsin would digest our stomachs since the stomach is made out of protein.

A Gastric ulcer is when ones stomach begins to digest itself. Gastric Ulcers are caused by a bacterial infection known as Helicobacter Pylori. Gastric Ulcers are cured with weeks of antibiotics.

While all of this is occuring the food
stays put in the stomach due to 2
sphincters. One is called the cardiac sphincter
which keeps the food from going up.
The 2nd is called the pyloric sphincter which keeps the food from going down.

The liver is responsible for the production of bile.
Bile is a chemical made from dead red blood cells.
Bile breaks down the fats that we eat.
After bile is produced it is stored in the gall bladder, it is released in the presence of fats in order to break them down.

Monday, January 7, 2008


All animals need to consume food to live. Oxygen and some sort of food source are needed for animals to grow. The raw materials are gained through eating and the oxygen is used in respiration which makes the energy needed for the synthesis of those raw materials into larger molecules.

Animals get their food in four different ways-

~Bulk Feeding~

Bulk Feeding is cosuming large concentrated portions of your food source.

~Fluid Feeding~

This is when organisms get theier nutrients from a liquid like blood or sap.

~Substrate Feeding~

Substrate feeding is when the organism spends part of its' life living in its food source.

~Filter Feeding~
This mode envloves the intake of huge amounts of your food source straight out of the environment.

Your digestive system is basically a really long tube where food products are broken down and the needed parts are absorbed the rest excreted as extracellular waste because it never actually entered your cells.

Food is pushed through the digestive track by involuntary muscle contractions known as peristalsis. According to Paige this is like an utter.

Digestion starts with Ingestion

Swallowing starts off the process the epiglottis (cartilage flap) closes securing itslef over your trachea preventing food from "going down the wrong pipe". Waves of muscle push the food towards the stomach which is where we finished our lesson.