The Brain

We started this week with an exam. I'm going to wait until I receive my exam back before I post any comments. The second half of the week we started to focus on the brain. We reviewed the three Primary Regions of the brain: Prosencephalon, Mesencephalon and Rhombencephalon. Then at week 8 of development we now have the Telencephalon (which as an adult becomes the cerebral hemispheres) the Diencephalon (becomes the Thalmus, hypothalmus), the Mesencephalon becomes the Midbrain (corpora quadrigemina), the Metencephalon in the adult brain develops the Pons and Cerebullum while the Myencephalon becomes the medulla oblongata.
We focused on the midbrain region. The Corpora Quadrigemina which has the superior colliculi (the relay system for vision impulses) and the inferior colliculi (relay system for auditory impulses). The tectum is the "roof" or dorsal surface of the midbrain. One thing that makes learning the human body so difficult is the vocabulary. Many words are spelled similarly but have a very different meaning, or there are multiple names for the same thing. We see this with the cerebral aqueduct which is the same as the aqueduct of Sylvius. Very confusing. We then took a quick overlook of the midbrain that extends inferiorly into the Pons and more inferiorly the medulla oblongota. If somebody is talking about the hindbrain they are referring to the Pons and the Medulla, but the term brain stem includes the midbrain, pons, and medulla. Just the beginning of this topic seems confusing with a lot of details. However, we move right along to the protective coverings of the brain (and spinal cord) the meninges. Of these there are three layers. The outermost consists of a thick, white, dense irregular connective tissue called the Dura Mater. Within this layer there are major blood vessels. The area above the Dura Mater is called the Epidural Space whereas the area below it is the sub-dural space. The dura mater around the brain is 2 layers thick, in contrast to only being one layer thick around the spinal cord. The middlemost layer is the Arachnoid Mater, this is web-like, contains no blood vessels and is found next to the sub-arachnoid space where CSF is and diffusions through CSF allows nutrients between these two layers. The third and innermost layer of meninges is the Pia Mater. It's structure is capillary network.
We took a closer look at the Dura Mater which is two layers. The Periosteal layer is closest to the skull and the meningeal layer is the inner layer. These two layers adhere tightly together however in some places spaces do form between the layers. One such space is the Superior Sagittal Sinus (where venous blood collects between the right and left cerebral hemispheres).
Next we turned to the blood flow of the brain. For this we referred to page 774 in our Primary textbook. It was pointed out that the falx cerebri was the region of dura mater between the cerebral hemisphers.
We followed the path of venous drainage: Superior sagittal sinus>Right transverse sinus>inferior sagittal sinus>left transverse sinus>Sigmoid sinus>internal jugular>right branchiocephal>Superior vena cava>heart.
Then we turned to page 757 and 758 and looked at Arterial Blood Circulation: Oxygenated blood from the lungs to the heart.
Blood enters the Left Atrium>(bicuspid/mitral valve) Left Ventricle>Semilunar valve>ascending Aorta>Aortic Arch>Descending Aorta>Thoracic Aorta>Abdominal Aorta
Focus was given to the three vessels which come off the Aortic Arch 1)Right branchiocephalic artery -right subclavian and right common carotid ....2) Left common carotid-external and internal 3) left subclavian Both internal carotids go through the neck; feed blood into the Circle of Willis.
These are the notes I took in class. I have to re-read over the material and study each of these components. A&P II has proven to be a lot different from A&P I. It's a challenge to comprehend everything you think you need to know and bringing the information from lecture and the four textbooks together.