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Circle of willis

This diagram shows a series of interconnected blood vessels and capillaries.
The blood supply to the brain enters through the internal carotid arteries and the vertebral arteries, eventually giving rise to the circle of Willis.

Watch this animation to see how blood flows to the brain and passes through the circle of Willis before being distributed through the cerebrum. The circle of Willis is a specialized arrangement of arteries that ensure constant perfusion of the cerebrum even in the event of a blockage of one of the arteries in the circle. The animation shows the normal direction of flow through the circle of Willis to the middle cerebral artery. Where would the blood come from if there were a blockage just posterior to the middle cerebral artery on the left?

Venous return

After passing through the CNS, blood returns to the circulation through a series of dural sinuses and veins ( [link] ). The superior sagittal sinus    runs in the groove of the longitudinal fissure, where it absorbs CSF from the meninges. The superior sagittal sinus drains to the confluence of sinuses, along with the occipital sinuses    and straight sinus    , to then drain into the transverse sinuses    . The transverse sinuses connect to the sigmoid sinuses    , which then connect to the jugular veins    . From there, the blood continues toward the heart to be pumped to the lungs for reoxygenation.

Dural sinuses and veins

This diagram shows a lateral view of the brain and labels the location of the different sinuses.
Blood drains from the brain through a series of sinuses that connect to the jugular veins.

Protective coverings of the brain and spinal cord

The outer surface of the CNS is covered by a series of membranes composed of connective tissue called the meninges    , which protect the brain. The dura mater    is a thick fibrous layer and a strong protective sheath over the entire brain and spinal cord. It is anchored to the inner surface of the cranium and vertebral cavity. The arachnoid mater    is a membrane of thin fibrous tissue that forms a loose sac around the CNS. Beneath the arachnoid is a thin, filamentous mesh called the arachnoid trabeculae    , which looks like a spider web, giving this layer its name. Directly adjacent to the surface of the CNS is the pia mater    , a thin fibrous membrane that follows the convolutions of gyri and sulci in the cerebral cortex and fits into other grooves and indentations ( [link] ).

Meningeal layers of superior sagittal sinus

This image shows a cross-section through the brain. The different meningeal layers are labeled.
The layers of the meninges in the longitudinal fissure of the superior sagittal sinus are shown, with the dura mater adjacent to the inner surface of the cranium, the pia mater adjacent to the surface of the brain, and the arachnoid and subarachnoid space between them. An arachnoid villus is shown emerging into the dural sinus to allow CSF to filter back into the blood for drainage.

Dura mater

Like a thick cap covering the brain, the dura mater is a tough outer covering. The name comes from the Latin for “tough mother” to represent its physically protective role. It encloses the entire CNS and the major blood vessels that enter the cranium and vertebral cavity. It is directly attached to the inner surface of the bones of the cranium and to the very end of the vertebral cavity.

Questions & Answers

Which of the following is generally called a Sprain?
Raneem Reply
sprain is also called torn ligament.. it is the streching Or tearing of ligament.. with in a joint
Khawaja
a long boin between your nick and pelvic
Marie
sprain is also known as" moch"
Sneha
sprain is also known as 'moch' it's a type of injury affect on ligaments..(sprain)
Sanjith
sprain and strain both called as 'moch'
Sanjith
body, muscle and regional of structures in the body
Harmony Reply
when the heart beats, blood pumps through the body and making the body function
Harmony
what is vagina
Hausa Reply
what is ventricular circulation
Maryam Reply
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In a four-chambered heart, such as that in humans, there are two ventricles that operate in a double circulatory system: the right ventricle pumps blood into the pulmonary circulation to the lungs, and the left ventricle pumps blood into the systemic circulation through the aorta.
yes
anjali
hi
A 23-year-old basketball player mentally rehearses free throw shots while lying in bed. Which option best describesthe area of the brain that is involved in generating a motor image of this action in the absence of actual movement?
Rai
hapothalamus
Prashant
a 67-year-old man has a stroke. one week later, he experiences sudden and uncontrolled flailing, ballistic movements of his limbs. which part of the man’s brain is most likely to have been damaged by the stroke?
Rai
primary motor cortex.. (principal area of cerebrum)
Khawaja
what factors that affect the rate diffusion
Gift Reply
the mass of the solute the temperature of theenvironment the solvent density and the distance traveled
Sulaiman
ok.
Thobok
sorry what are the common meaning of haemostatis
Juma Reply
homeostasis is the steady internal physical and chemical conditions maintaining by living systems
Sulaiman
what are the negatives feedback regulation of ADH
Nansi Reply
what is the the differences between DNA and RNA?
Mustapha
The major differences between the DNA and RNA are contain of double stranded and single stranded which the DNA contain duoble stranded and RNA contain single stranded.
Juma
what are the negatives feedback regulation of ADH before this we confused just verify long term of ADH firstly
Juma
How many genes consist of DNA?
Omaryare
omaryare muhyadiin when you talk about genes, is the material formed in a DNA genes have form like plasma have many genes round there
Juma
aldosterone, renin
Conan
DNA contains the sugar deoxyribone while RNA contains the sugar ribose the only difference between ribose and deoxyribone is that ribose has one more- OH group than deoxyribone which has -H attached to the second carbon in the ring DNA is a double stranded molecules RNA is a single strnded molecul
Sulaiman
yes
Thobok
in human genes very in size from a few hundred DNA based to more than 2million bases
Sulaiman
to know the different structures of the body To know how the body works To know more about our body parts
Deitdre Reply
hi Deitdre you tock about knowledge or you ask the question
Juma
do you need any explanation when reading this book?
janet Reply
Its Good
Hashir
yes
Balogun
Yes
Mariam
yes
Sale
yes
Mustapha
if have many ability just do it!!
Juma
we all waiting for it
Sulaiman
compare and contrast the operation of homeostasis
Dinelle Reply
what is the difference between an ionic, polar covalent and nonpolar covalent bond?
Dinelle
In summary, the bond has different in electronegativity.
Balogun
sorry help me to get the definition of hemostasis or the meaning
Juma
the definition of distal
Dinelle Reply
farthest away from the attachment point.
felix
Distal, is the farthest possition from the origin or midle point
Juma
exercise physiologist how ?
Noor Reply
hi noorr. when you talk about physiologist its a person who study physiology but exercise physiologist is what an exercise doing by physiologist in physiologican
Juma
can I get the questions of human physiology that is present in HSC 2nd semester
Rafiullah Reply
in my lerning the question com like for example ni eassy qustion must understand the the part of the body and how it work or mechanisms of each part learned
Juma
how can I memorize
mukhtaar Reply
which part of the body produces blood
aadil
give me answer
aadil
Red blood cells are formed in the red bone marrow ofbones. Stem cells in the red bone marrow called hemocytoblasts give rise to all of the formed element
mukhtaar
what is hemocytoblasts
Fatima
hemocytoblasts are stem cells in red bone marrow which give rise the all of formed elements
Khawaja
Discuss clonal theory in physiology and its application in measles infection in a 6yr child? Can anyone help me
Isaac Reply

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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