THE HEAD AND NECK. 



'37 



Two systems of circulation are given off from the circle of Willis: (i) 

 Tlic ganglionic ; (2) tlie cortical. You have just seen the ganglionic or end 

 arteries entering the brain by the perforated spaces. The cortical arteries and 

 their veins form the woof of the pia mater, the warp of which is connective tissue. 



i . From what source docs the brain receive its blood ? 

 The brain is supplied with blood by the circle of Willis. 



OPTIC THALAMUS 



OPTIC TRACT 

 TUBER CINEREUM 



POSTERIOR PER- 

 FORATED SPACE 



CORPUS GENICU- 

 LA TUM EXTKRNUM 



CORPUS GENICU- 

 LA TUM INTERNUM 



PYRAMIDAL BODY 

 OLIVARY BODY 



ARCIFORM FIBRES 



ISLAND OF REIL 

 PITUITARY BODY 



CORPORA 

 ALBICANTIA 



CRUS CEREBRI 



PONS VAROLII 



GREA T HORIZONTA L 



FISSURE 

 FLOCCULUS 



FORAMEN CAECUM 



SPIN A L A CCESSOR Y 

 NERVE 



FIRST CER VICAL NER VE 



ANTERO-LATERAL GROOVE 



OF SPINAL CORD 

 ANTERIOR COLUMN OF 

 SPINAL CORD 



FIG. 92. SURFACE ORIGIN OF THE CRANIAL NERVES. (After Allen Thomson. Quain.) 



2. How is this circle formed ? 



It is formed by an anastomosis between branches of the internal carotid and 

 vertebral arteries. 



3 . How does the internal carotid reach the brain ? 



It comes through the carotid canal and sphenotic foramen, and gives off: (i) 

 The anterior cerebral ; (2) the middle cerebral ; (3) the posterior communi- 

 cating. 



4. Hoiv docs the vertebral artery reach tJie brain ? 



It passes through the foramina in the transverse processes of the cervical 

 vertebrae and the foramen magnum. It divides into the two posterior cerebral 

 arteries. 



5 . How is the blood returned from the brain / 



The blood from the ganglionic system is returned to the straight sinus by 



