Cranial Nerves

There are 12 cranial nerves attached to the under side of the brain. CN 1 is the Olfactory nerve which is your sense of smell. CN 2 is the Optic nerve which is your sight. CN 8 is the Vestibulocochlear nerve which is your hearing. CN 1, 2, and 8 are afferent or sensory only.

CN 3 is the Oculomotor nerve it controls the Superior and Inferior Rectus, Inferior Oblique, and Medial Rectus muscles. CN4 is the Trochlear nerve controls the Superior Oblique muscle. CN 6 is the Abducens which controls the Lateral Rectus muscle. CN 11 is the Accessory nerve which controls the Pharynx, Larynx, and Soft Palate that are used in swallowing. CN 12 is the Hypoglossal nerve which controls the tongue. CN 3, 4, 6, 11, 12 are motor neurons or efferent.

CN 3 is the oculomotor nerve which also adjusts your pupil size. CN 7 is the Facial nerve controls muscles in the face, neck, and scalp. It also controls your lacrimal glands (tear producing) and sublingual and submandibular glands (which produce saliva). CN 9 is the Glossopharyngeal nerve that control tastebuds in the posterior 1/3 of the tounge, controls muscles in swallowing. Also stimulates the Parotid gland to secrete saliva. CN10 is the Vagus nerve that controls taste buds in the epiglottis and pharynx. Also controls muscles in the neck and throat. Monitors blood pressure and respiratory function. It also controls smooth muscle in the Gi tract, respiratory passageway, esophagus, stomach, gallbladder, small intestines, and large intestines. CN3, 7, 9, and 10 are all part of the parasymathetic nervous system.

You can click on the picture to enlarge and read.

Fetal Blood flow

Blood from the mother and fetus exchange food and oxygen for carbon dioxide and wastes in the placenta. Because a fetus is growing so fast their blood has about 50% more hemoglobin in it to provide much more oxygen to the fetus. Blood flows from the placenta up through the umbilicus and into the fetus. There is about half of it goes to the liver and the other have go into the Ductous Venosus. After a short distance the Ductous Venosus joins the Inferior Vena Cava. Here the blood goes into the Right Atrium and splits again. Some goes into the Right Ventricle and some goes through a hole in the heart called the Foramen Ovale into the Left Atrium. Now most of the blood bypasses the lungs through a vessel called the Ductous Arteriosus which shunts blood from the Pulmonary Trunk into the decending arch of the Aorta. The blood travels down the aorta and splits again. Some goes out to the parts of the body and the rest is taken out to the placenta by the umbilical arteries.


After the baby is born the Ductous Venosus becomes the Ligamentium Venosum which no longer carries blood. The Foramen Ovale will become the Fossa Ovalis which closes the hole in the Right Atrium to the Left Atrium. The Ductous Arteriosus become the Ligamentium arteriosum and the shunt from the pulmonary trunk to aorta is closed. This happens over a short period of time after the baby is born not just as it exits the mother. This link is helpful in explaining what happens. http://www.cayuga-cc.edu/people/web_pages/greer/biol204/heart4/heart4.html

Blood Types

There are four types of blood in the human body. They are O, A, B, and AB. As with the chart above each type has an antigen on the surface of every RBC except type O. This is the reason type O is the universal donor however type O people can only receive type O blood. The RBC's won't present an antigen for the immune system to recognize as a foreign substance in the body. Conversely type AB is the universal recipient because it has all the antibodies present, types A, B, AB, and O can all be given to someone with AB blood. The last part of this is the RH factor. This is where + or - come into play. Each blood type has a RH component so there is O+/-, A+/-, B+/-, and AB+/-. The plus simply means there is a marker on the RBC that is not present in the negative. This makes O negative as the universal donor and AB+ as the universal recipient. This chart summes everything up.

Recipient[1]	Donor[1]
	O−	O+	A−	A+	B−	B+	AB−	AB+
O−	Y
O+	Y	Y
A−	Y		Y
A+	Y	Y	Y	Y
B−	Y				Y
B+	Y	Y			Y	Y
AB−	Y		Y		Y		Y
AB+	Y	Y	Y	Y	Y	Y	Y

Blood Flow Around the Heart

Blood moves to fast through the heart for the blood to nourish the heart. The heart is always pumping from before you are born till you die thus using a lot of nutrients and oxygen. Therefore once blood leaves the heart and enters the ascending aorta it branches off and supplies the heart with blood to give oxygen and nutrients and take away carbon dioxide and waste products. Arteries leaving the aorta are the Right Coronary artery which branches into the Right Marginal artery and the Posterior Interventricular artery (which goes around to the posterior of the heart from the bottom. The other branch is the Left Coronary artery which branches into the Anterior Interventricular artery and the Circumflex artery.

Blood is returned to the heart with three viens. The Great Cardiac vein which is beside the Anterior Interventricular artery. The Middle Cardiac vein which is beside the Posterior Interventricular vein. And finally the Lesser Cardiac vein which is beside the marginal artery. These three veins all dump into the Coronary Sinus which drains into the heart.

The Heart

The heart is what moves blood through the body. Blood first enters the heart at the Right Atrium from the Superior and Inferior Vena Cava. Here the blood goes through the Tricuspid valve into the Right Ventricle. On the next contraction the blood goes through the Pulmonary Valve and into the Pulmonary Trunk which splits into the right and left Pulmonary Arteries. Here is where the artery is pumping non-oxygenated blood into the lungs. After the gasses are exchanged in the lungs, (carbon dioxide for oxygen) through capillary networks, the blood goes back to the heart through the right and left Pulmonary Veins. Blood enters the Left Atrium fully oxygenated. Then the blood goes through the Bicuspid (Mitral) Valve into the Left Ventricle. Here blood is pumped into the Aorta to be distributed to the rest of the body through the Aortic Valve.

Blood

Blood is made of both plasma and formed elements. Plasma is a watery liquid which contains dissolved substances. The formed elements are mostly Red Blood Cells but also a very small percentage of White Blood Cells and Platelets. RBC's are what carry oxygen to cells and carbon dioxide away from cells. RBC's live approximately 120 days. WBC's are what make up part of your immune system. Platelets are cell fragments that are a big part of clotting after you have damaged a blood vessel. Blood cells are made in the Red Bone Marrow which in adults is mostly in the tips of long bones and in the flat bones of the body.

Blood keeps the body alive by giving the cells the nutrients and oxygen they need to survive. It takes away the wastes that are hazardous to the cells. Cells undergoing mitosis use alot of oxygen and nutrients because its a very energy intensive process.

Circle of Willis

The Circle of Willis is the spot where blood is brought to the brain to be distributed to the different lobes. It is made up of the Right and Left posterior communicating arteries and the anterior communicating artery. Blood is brought up from 2 different paths to make a anatomical redundancy. Blood flows from the left ventricle to the aortic arch then splits right into the Brachiocephalic artery then to the right common carotid, then to the right internal carotid artery to the Circle of Willis. This happens on the left side as well but there is no Brachiocephalic artery. It also receives blood from the left and right Subclavian to the right and left Vertebreal artery then join at the Basilar then up to the Circle of Willis. This system helps assure that if there is a problem with blood flow from one source there is still a chance for blood to make it to the brain because after about 4 minutes of no oxygen to the brain, cells start to die and permanent brain damage can occur. Here is a web site with a picture to see more clearly en.wikipedia.org/wiki/Circle_of_Willis

This happens all the time in all of us and helps ensure plenty of oxygen make it to the brain which is the most important organ in our bodies. Though i guess with modern technology you can still live with machines causing you to breath and circulate blood. I'm not sure if that would still be considered living or not and since the case of the Schiavo's where she was in a comatose state for 13 years and they decided to pull the plug and allow here to die that maybe it wouldn't be considered living. In this case the courts and even the congress got involved with the decision where the husband won and the parents lost. My personal opinion is the parents couldn't let go of there child (which i can understand somewhat) but after a certain amount of time i think its time to let go. Someday she may have been able to be revived if medicine gets to that point but to my knowledge they aren't that close so who knows how long it would be before this could happen.