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The blood flows in two separate loops.


The right side of the heart controls the pulmonary loop.

The left side of the heart controls the systemic loop.

The Pulmonary Loop

Circulatory system
(From www.pinterest.com)

Blood enters the heart through two large veins, the superior vena cava (9) and the inferior vena cava (10), emptying oxygen-poor blood from the body into the right atrium (11).

Blood flows from the right atrium into the right ventricle (1) through the open tricuspid valve. When the ventricles are full, the tricuspid valve shuts. This prevents blood from flowing backwards into the atrium while the ventricle contracts.

When the ventricle contracts, blood leaves the heart through the pulmonic valve and moves through the pulmonary arteries (2) to the lung capillaries (3).

Here, carbon dioxide passes from the blood to the lungs, and oxygen moves from the lungs into the blood.

The oxygenated blood travels through the pulmonary veins to the left atrium (4).

The Systemic Loop

Blood flows from the left atrium into the left ventricle (5) through the open mitral valve. When the ventricle is full, the mitral valve shuts. This prevents blood from flowing backward into the atrium when the ventricle contracts.

Blood leaves the heart through the aortic valve into the aorta (6).

The aorta branches just above the heart to form the arteries that supply blood to the upper and lower body.

The arteries divide into arterioles and then into capillaries (7 and 8).

The capillaries join together to form the venules that feed the veins.

All of the blood from the body is eventually collected into the two venae cavae, and the cycle repeats.

It takes about 30 s for a given portion of the blood to complete the entire cycle: from heart to lungs, back to the heart, out to the body, and back to the heart.


No, polar hormone molecules do not pass through cell membranes.


A hormone is a regulatory chemical that is secreted into the blood.

The blood carries a hormone to every cell in the body, but only the target cells for that hormone can respond to it.

Nonpolar hormones like steroids can pass through the plasma membrane unaided, but polar hormones like amino acid derivatives cannot pass through the membrane.

Hormone Types
(From Stark home page)

We can consider the action of a hormone to consist of three stages: (1) reception, (2) transduction, and (3) response.

(1) Reception

Polar hormones bind to receptors on specific transmembrane proteins.


(2) Transduction

The binding induces a change in the conformation of the inside part of the protein.

This in turn activates a cascade of enzyme activity within the cell.


(3) Response

The final step results in a specific action by the cell.

Each enzyme in the cascade can act on many succeeding molecules, so the response can be amplified by a factor of #10^8#.


#((cancel30^2 " beats")/(cancel15 cancel" seconds"))((60 cancel" seconds")/(1 " minute"))=(120 " beats")/"minute"#


Usually heart rate is measured in #"beats"/"minute"#, and so we can find that by saying:

#((cancel30^2 " beats")/(cancel15 cancel" seconds"))((60 cancel" seconds")/(1 " minute"))=(120 " beats")/"minute"#

By the way, a cat's normal heart rate is between 140 and 220 beats per minute, so this cat's owner should be calling the vet!



The nervous system and sensory system are what allow us to detect and respond to stimuli.


While sometimes they are lumped together, I think it is reasonable to classify each system as their own.

Sensory system: the system made up of the body parts that allow for the five senses of sight, hearing, taste, touch, and smell, and the sensory aspect of balance that occurs in the inner ear.

Nervous system: organ system including the brain, spinal cord, and all nerves found throughout the body. This system is what processes information received from nerves and the sensory system.

This shows the nervous system.

This shows the aspects of the sensory system.
These two systems work in close capacity with each other to absorb all types of information from the outside world and process it.

Our sensory organs absorb information and send it to the brain via nerves.

In the brain the information is processed, and used to make decisions as to what the appropriate response to this stimuli is.

The link below has an excellent overview of how we process information we absorb.



No - women don't have a prostate and so therefore can't get prostate cancer.


The prostate is an organ in male mammals. The urethra of a male mammal runs through the prostate, which nourishes and protects sperm as they make their way from the testes to the penis.


Since women and female mammals in general don't have a prostate, they can't get prostate cancer.



Liver supplies emulsifying bile juice to duodenum.


Liver is a very important organ. It prduces bile juice which is not enzymatic but there are bile salts present in the juice. The juice is temporarily stored in a small sac like organ called gall bladder .

As the half digested food (chyme ) enters duodenum from stomach, the gall bladder is given signal to contract. Bile is thus poured in duodenal cavity through duct.



Bile salts present in the juice acts as emulsifier on dietary fat globules which has reached duodenum with chyme. Large fat droplets are transformed into microscopic aggregates called micelle. Fat digesting enzymes (lipases) can now act on large fat molecules and break them into absorbable smaller molecules (glycerol and fatty acids).



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