Crosssection Through The Medulla Figure

A. Medial structures

1. The hypoglossal nucleus of CN XII

2. The medial lemniscus, which contains crossed fibers from the gracile and cuneate nuclei

3. The pyramid (corticospinal tracts)

Third ventricle

Pineal body Superior colliculus

Inferior colliculus CN IV

Facial colliculus Vestibular area

Hypoglossal trigone Vagal trigone

Third ventricle

Pineal body Superior colliculus

Inferior colliculus CN IV

Facial colliculus Vestibular area

Hypoglossal trigone Vagal trigone

Gracile And Cuneate Tubercles
Thalamus

Lateral geniculate body Medial geniculate body Crus cerebri

Superior cerebellar peduncle Middle cerebellar peduncle Inferior cerebellar peduncle

Striae medulläres

Cuneate tubercle

Gracile tubercle Cuneate fasciculus Gracile fasciculus

Figure 9-1. The dorsal surface of the brain stem. The three cerebellar peduncles have been removed to expose the rhomboid fossa. The trochlear nerve is the only nerve to exit the brain stem from the dorsal surface. The facial colliculus surmounts the genu of the facial nerve and the abducent nucleus. CN = cranial nerve.

Olfactory trigone Anterior perforated substance Interpeduncular fossa

Crus cerebri (cerebral peduncle)

Pons

Middle cerebellar peduncle

Brainstem And Cranial Nerves

Figure 9-2. The ventral surface of the brain stem and the attached cranial nerves (CN).

CN XII Olive Pyramid Cervical nerve

(Voifactory bulb (CN I) Optic chiasm —Olfactory tract

Infundibulum Tuber cinereum Mamillary body

Optic tract

CN III CN IV

CN V (motor root) CN V (sensory root) CN VI CN VII -CN VII (intermediate) CN VIII CN IX CN X CN XI

Pyramidal decussation

Figure 9-2. The ventral surface of the brain stem and the attached cranial nerves (CN).

Vestibular nuclei

Nucleus ambiguus (CN X)

Nucleus Ambiguus

CN X Spinal lemniscus

Inferior olivary nucleus

CN XII Pyramid

Medial lemniscus

Figure 9-3. Transverse section of the medulla at the midolivary level. The vagal nerve [cranial nerve (CN) X], hypoglossal nerve (CN XII), and vestibular nerve (CN VIII) are prominent in this section. The nucleus ambiguus gives rise to special visceral efferent fibers to CN IX, X, and XI.

CN XII Pyramid

Medial lemniscus

Hypoglossal nucleus of CN XII Solitary tract and nucleus Dorsal motor nucleus of CN X Inferior cerebellar peduncle

Vestibular nuclei

Hypothalamospinal tract Spinal trigeminal nucleus Spinal trigeminal tract

Nucleus ambiguus (CN X)

CN X Spinal lemniscus

Inferior olivary nucleus

Figure 9-3. Transverse section of the medulla at the midolivary level. The vagal nerve [cranial nerve (CN) X], hypoglossal nerve (CN XII), and vestibular nerve (CN VIII) are prominent in this section. The nucleus ambiguus gives rise to special visceral efferent fibers to CN IX, X, and XI.

B. Lateral structures

2. The vestibular nuclei (CN VIII)

3. The inferior cerebellar peduncle, which contains the dorsal spinocerebellar, cu-neocerebellar, and olivocerebellar tracts

4. The lateral spinothalamic tract (spinal lemniscus)

5. The spinal trigeminal nucleus and tract of CN V

III. CROSS-SECTION THROUGH THE PONS (Figure 9-4). The pons has a dorsal tegmentum and a ventral base.

A. Medial structures

1. Medial longitudinal fasciculus

2. Abducent nucleus of CN VI (underlies facial colliculus)

3. Genu (internal) of CN VII (underlies facial nerve) [facial colliculus]

4. Abducent fibers of CN VI

5. Medial lemniscus

6. Corticospinal tract (in the base of the pons)

B. Lateral structures

1. Facial nucleus (CN VII)

2. Facial (intraaxial) nerve fibers

3. Spinal trigeminal nucleus and tract (CN V)

4. Lateral spinothalamic tract (spinal lemniscus)

5. Vestibular nuclei of CN VIII

6. Cochlear nuclei of CN VIII

Figure 9-4. Transverse section of the pons at the level of the abducent nucleus of cranial nerve (CN) VI and the facial nucleus of CN VII. MLF = medial longitudinal fasciculus.

Pons Cross Section

Figure 9-4. Transverse section of the pons at the level of the abducent nucleus of cranial nerve (CN) VI and the facial nucleus of CN VII. MLF = medial longitudinal fasciculus.

Corticospinal tract7 Trapezoid body

Corticospinal tract7 Trapezoid body

Cerebral Aqueduct

Oculomotor nucleus

Medial lemniscus

CN III

Cerebral peduncle (crus cerebri) Corticospinal tract Red nucleus

WW! %IWVMMIMMI tTclCt

Spinal

Medial geniculate body

Cerebral aqueduct

Superior colliculus

Periaqueductal gray

Dentatothalamic tract

Substantia nigra

Figure 9-5. Transverse section of the midbrain at the level of the superior colliculus, oculomotor nucleus of cranial nerve (CN) III, and red nucleus. MLF = medial longitudinal fasciculus.

IV. CROSS-SECTION THROUGH THE ROSTRAL MIDBRAIN (Figure 9-5). The midbrain has a dorsal tectum, an intermediate tegmentum, and a base. The aqueduct lies between the tectum and the tegmentum.

A. Dorsal structures include the superior colliculi.

B. Tegmentum

1. Oculomotor nucleus (CN III)

2. Medial longitudinal fasciculus

3. Red nucleus

4. Substantia nigra

5. Dentatothalamic tract (crossed)

6. Medial lemniscus

7. Lateral spinothalamic tract (in the spinal lemniscus)

C. Crus cerebri (basis pedunculi cerebri, or cerebral peduncle). The corticospinal tract lies in the middle three-fifths of the crus cerebri.

V. CORTICOBULBAR FIBERS (see also Figure 13-4) project bilaterally to all motor cranial nerve nuclei except the facial nucleus. The division of the facial nerve nucleus that innervates the upper face (the orbicularis oculi muscle and above) receives bilateral cor-ticobulbar input. The division of the facial nerve nucleus that innervates the lower face receives only contralateral corticobulbar input.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

Get My Free Ebook


Responses

  • John
    Where does the brain stem attach?
    6 years ago

Post a comment