Meninges, CSF and Blood Supply of the Head and Neck

1. Meninges, CSF and Blood Supply of the Head and Neck Ruhaizan, Diyana, Fatimah, Fadhila, Marshitah, Marzura, Sakinah

2. Meninges (singular: Meninx) • Def: 3 membranous envelopes; Dura mater, Arachnoid and Pia Mater - surrounding brain and spinal cord • Functions: • Protecting the brain and spinal cord from mechanical injury • Providing blood supply to skull & hemispheres • Providing a space for the flow of CSF

3. Meninges Dura mater -most superior -toughest & inflexible -”Tough mother” (latin name) Arachnoid -middle layer -Spider web-like of blood supply Pia mater -innermost layer -”tender mother” (latin name)

4. Production of CSF • Cerebrospinal Fliud (CSF) is a clear fluid produced by dialysis of blood in the choroid plexus. • Further production also comes from the ependymal cell linings and vessels within the pia mater. • Edendymal cell production of CSF is via ultrafiltration of blood plasma and active transport across the ependymal cells.

5. Production of CSF • Of the total CSF production, 35% is produced within the third ventricle of the brain, 23% via the fourth ventricle and 42% from general ependymal cell filtration.

6. Function of CSF • Cerebrospinal fluid (CSF) surrounds the brain as well as the central canal of the spinal cord. • It helps cushion the central nervous system (CNS), acting in a similar manner to a shock absorber.  •  It also acts as a chemical buffer providing immunological protection and a transport system for waste products and nutrients. 

7. Function of CSF • The CSF also provides buoyancy to the soft neural tissues which effectively allows the neural tissue to "float" in the CSF  prevents the brain tissue from becoming deformed under its own weight. •  It acts as a diffusion medium for the transport of neurotransmitters and neuroendocrine substances.

8. Flow of CSF Hydrostatic pressure CSF (from choroid plexus) Interventricular Foramina 3rd Ventricle (located in diechephalon) Through cerebral aqueduct 4th Ventricle (located in hindbrain) Central canal of spinal cord Subarachnoid Space Cerebromedullary cistern Flows down the length of spinal cord in the subarachnoid space Dura & ArachnoidMeninges Drained into venous sinuses (through arachnoid granulation in dorsal sagittal sinus) Circulate over the cerebral hemisphere

10. MAJOR ARTERIES SUPPLYING HEAD AND NECK

11. Arteries supplying Head & Neck The major arteries supplying head and neck derived from : • Common carotid i. internal carotid artery ii. External carotid artery • Subclavian arteries • Vertebral artery (branched from 1st part of subclavian a.)

12. Common Carotid Artery • CCA runs upwards to the sup. border of thyroid cartilage at C3 • Bifurcates into external and internal carotid a.

13. Blood supply- Arteries • The external carotid artery: provides the major blood supply for the face and mouth. • The two major terminal branches of the external carotid artery: • the maxillary arteries • facial arteries

14. Blood supply- Arteries

15. Blood supply- Arteries • The maxillary artery is the large of the two terminal branches of the external carotid artery. • It arises behind the angle of the mandible and supplies the deep structures of the face.

16. Blood supply- Arteries • Major branches of the maxillary artery: • Infraorbital artery • Posterior superior alveolar artery • Inferior alveolar artery 1 2 3

17. Blood supply- Arteries • Infraorbital artery gives branches to anterior and middle superior alveolar arteries. Their distribution to the maxillary incisors and canine teeth and to the maxillary sinuses. • Posterior superior alveolar artery. Its distribution is to the maxillary molar and premolar teeth and gingiva. • Inferior alveolar artery. It descends close to the medial surface of the mandibular ramus to the mandibular foramen. Before entering the foramen, it gives off the mylohyoid branch which supplies tissues in the floor of the mouth.

18. Blood supply- Arteries • The facial arteryis the other major branch of the external carotid artery. • It enters the face at the inferior border of the mandible. It passes forward and upward across the cheek towards the angle of the mouth. • It continues upward along the side of the nose and ends at the medial canthus (inner corner) of the eye.

19. Blood supply- Arteries • The lingual artery also is a branch of the external carotid artery. • Its distribution is along the surface of the tongue.

20. Internal Carotid Artery • There are no branches of ICA in the neck; passes superiorly in the neck within carotid sheath anterior to transverse process of upper cervical vertebrae and enters skull through carotid canal • At its root, ICA has a dilatation area a.k.a carotid sinus • Inside skull, gives off to opthalmic a. (supplies optic nerve, eye, orbit an scalp)

21. Arterial supply of the brain • Normally divided into anterior and posterior cerebral circulation • Two main pair of artery supplying cerebral artery and cerebrum: • Internal carotid artery • Vertebral artery

22. Venous Drainage of the Head and Neck • The veins of the head and neck collect deoxygenated blood and return it to the heart. • Anatomically, the venous drainage can be divided into three parts: • Venous drainage of the brain and meninges: Supplied by the dural venous sinuses • Venous drainage of the scalp and face: Drained by veins synonymous with the arteries of the face and scalp. These drain into the internal and external jugular veins. • Venous drainage of the neck: Carried out by the anterior jugular veins.

23. External Jugular Vein • The external jugular vein and its tributaries supply the majority of the external face. • It is formed by the union of two veins: • Posterior auricular vein - drains the area of scalp superior and posterior to the outer ear. • Retromandibular vein (anterior branch) – itself formed by the maxillary and superficial temporal veins, which drain the face.

24. External Jugular Vein

25. Anterior Jugular Veins • The anterior jugular veins vary from person to person. • They are paired veins, which drain the anterior aspect of the neck. • Often they will communicate via a jugular venous arch. • The anterior jugular veins descend down the midline of the neck, emptying into the subclavian vein.

26. Anterior Jugular Veins

27. Internal Jugular Vein • The internal jugular vein (IJV) begins in the cranial cavity, as a continuation of the sigmoid sinus • The initial part of the IJV is dilated, and is known as the superior bulb.  • The vein exits the skull via the jugular foramen.

28. Internal Jugular Vein • In the neck, the internal jugular vein descends within the carotid sheath, deep to the sternocleidomastoid, and lateral to the common carotid artery. • At the bottom of the neck, posteriorly to the sternal end of the clavicle, the IVJ combines with the subclavian vein to form the brachiocephalic vein. • Immediately before its termination, the inferior end of internal jugular vein dilates, to form the inferior bulb of the IJV. 

29. Internal Jugular Vein

30. Dural Venous Sinuses • The dural venous sinuses are spaces between the periosteal and meningeal layers of dura mater, which are lined by endothelial cells. • They collect venous blood from the veins that drain the brain and bony skull, and ultimately drain into the internal jugular vein.

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