dlasfen.blogg.se - Head and neck diagrams

Lower brain functions related to breathing, heart rate, and reflexes are controlled by the brain stem.

The base of the brain that connects to the spinal cord is the brain stem.

Yet being an extremely complex organ, the brain can be further divided into many anatomically distinct regions with distinct functions. The interior of the brain contains mostly white matter that connects the processing areas of gray matter to each other and to all of the muscles and sensory receptors in the body. Around 100 billion neurons in the gray matter of the brain control almost all of the body’s activities, including the conscious activities of the mind and the subconscious activities that control the organs and lower bodily processes. However, the ophthalmic artery is present pretty much all of the time.The brain weighs in at around three pounds on average, making it one of the most massive organs in the human body. These branches of the ICA are generally tiny and inconsistent, and often they might not be present.

According to this classification, the ICA slits into seven parts named as C1 to C7, with each part providing branching into different vessels. įurthermore, the neurologists, neuroradiologists, and neurosurgeons also use the Bouthillier classification to split the ICA into different parts based on the angiographic appearance of the vessel. The ophthalmic artery branches off the cavernous portion of the ICA while the MCA and ACA are branches of the cerebral ICA. These sections include the cervical, petrous, cavernous, and cerebral parts of the ICA. Moreover, the course of the ICA is divided into four sections, depending on where the artery is currently traveling. The ophthalmic artery is responsible for blood supply to the inner layers of the retina, as well as supplying other parts of the orbit, meninges, face, and upper nose. The ACA is responsible for supplying the motor and sensory cortices of the lower limb. The MCA is responsible for supplying the motor and sensory cortices of the upper limb and face, as well as the Wernicke area of the temporal lobe and Broca’s area of the frontal lobe. At the circle of Willis, the ICA branches to become the middle cerebral artery (MCA) and anterior cerebral artery (ACA). On the other hand, the ICAs anastomose with the branches of the basilar artery to form the circle of Willis. The ECA has eight branches, which anastomose with the branches from the contralateral external carotid, allowing for collateral circulation: These branches include

After its division, the ECA exits the sheath to provide oxygenated blood to the face and neck, while the ICA continues in the carotid sheath to enter the carotid canal within the temporal bone. The carotid sinus baroreceptors respond to changes in the stretch of the blood vessel and are responsible for detecting changes and maintaining blood pressure. The carotid body chemoreceptor is sensitive to decreased PO2, increased PCO2, and decreased pH of blood, and is responsible for alerting the brain to change the respiratory rate. This bifurcation point is clinically significant as it serves as a point for the location of the "carotid body," a chemoreceptor, and the "carotid sinus," a baroreceptor. At the location of the upper border of the thyroid cartilage (typically at the level of the fourth or fifth cervical vertebra), the common carotid arteries bifurcate into the ECA and ICA. The carotid arteries originate posterior to the sternoclavicular joints and in the neck, they are contained within the carotid sheath posterior to the sternocleidomastoid muscle. The tunica adventitia attaches the carotid vessel to the surrounding tissue. Smooth muscle comprises the tunica media, and it is responsible for changing the diameter of the blood vessel to regulate blood flow and blood pressure. Like most of the vascular system throughout the body, histologically, the carotid arteries are made up of three layers – the inner layer "tunica intima," the middle layer "tunica media," and the outer layer "tunica adventitia." The tunica intima consists of endothelium supported by a fragile elastic and also a collagenous layer of variable thickness.