Corpus callosum

The corpus callosum (CC) links the cerebral cortex of the left and right cerebral hemispheres and is the largest fibre pathway in the brain.

Gross anatomy

The corpus callosum is ~10cm in length and is C-shaped, like most of the supratentorial structures, in a gentle upwardly convex arch.

It is divided into four parts (anterior to posterior):

• rostrum (continuous with the lamina terminalis)
• genu
• trunk/body
• splenium

Relations

Immediately above the body of the CC, lies the interhemispheric fissure in which runs the falx cerebri, the anterior cerebral vessels. The superior surface of the CC is covered by a thick layer of grey matter known as the indusium griseum.

On either side, the body is seperated from cingulate gyrus by the callosal sulcus.

Attached to the concave undersurface of the CC is the septum pellucidum anteriorly, and the fornix and its commissure posteriorly.

Fibre tracts

Although the CC can be seen as a single large fibre bundle connecting the two hemispheres, an number of individual fibre tracts can be identified. These include:

• genu: forceps minor : connect medial and lateral surfaces of the frontal lobes
• rostrum: connecting the orbital surfaces of the frontal lobes
• trunk (body): pass through the corona radiata to the surfaces of the hemispheres
• trunk and splenium: tapetum; extends along the lateral surface of the occipital and temporal horns of the lateral ventricle
• splenium: forceps major; connect the occipital lobes

These connections can also be divided into :

• homotopic connections  those that link similar regions on each side e.g. visual fields of motor/sensory areas of the trunk
• heterotopic connections: those that link dysimilar areas

Blood supply

The corpus callosum (CC) has a rich blood supply, relatively constant and is uncommonly involved by infarcts. The majority of the CC is supplied by the pericallosal arteries (the small branches and accompanying veins forming the pericallosal moustache) and the posterior pericallosal arteries, branches from the anterior and posterior cerebral respectively. In 80% of patients additional supply comes from the anterior communicating artery, via either subcallosal artery or median callosal artery.

• subcallosal artery (50% of patients) is essentially a large version of a hypothalmic branch, which in addition to supplying part of the hypothalamus also supplies the medial portions of the rostrum and genu

• median callosal artery (30% of patients) can be thought of as a more extended version of the subcallosal artery, in that it travels along the same course, supplies the same structures but additionally reaches the body of the corpus callosum

• posterior pericallosal artery (also known as splenial artery) supplies a variable portion of the splenieum. Its origin is inconstant, arising from P3 or branches there of

The hippocampus on MRI

Coronal images of the head (A), body (B) and tail (C) and a sagittal cross-section of the hippocampus (D) on low resolution 1mm3 T1 1.5 T images (A–D) and on high resolution 0.7 mm3 T2 7 T images (E–H). Note the white matter bands between the dentate gyrus and cornu ammonis on the high resolution T2 images (indicated by arrows). Although we show high resolution 7 T T2 images here, the white matter bands between the dentate gyrus and the cornu ammonis can also be visualized on high resolution T2 3–4 T images

University of Winsconsi's Neuroanatomy Resources

Spinal cord: Global Spinal cord
Spinal cord: Clinical Spinal cord	Spinal cord levels
Brain stem: Global Brain stem	Virtual Brain stem
Cerebellum: Global Cerebellum

Thalamus: Global Thalamus	Thalamus/Hypothalamus/Basal ganglia identifications
Cranial Nerves: Cranial Nerve Review
National Boards: National Board Review; Practice questions

Neurosciences video demonstrations	Radiology reference page	Ventricles
Neuroanatomy identifications	CNS Development	Sleep (ppt)
Learn@UW	Clinical gallery	Coma (ppt)

Week Number	Self Learning
2 : Jan 23 - 27	Blood supply Spinal cord levels

Territories of Brain Arteries

Dissecting the BioDigital Human: A 3D Anatomy Lesson

The Sensory Neurons of Touch

Lymphatic drainage of the head and neck

INTRODUCTION

THE lymphatic tissue of the head and neck forms one third of the lymphatic tissue of the body

The lymphatic tissue of the head and neck is divided into the adenoid tissue and lymph nodes

1-the adenoid tissue

it is aggregation of lymphoid tissue which guards the entrance of the alimentary and respiratory system tracts

so it forms a ring called the lymphatic ring or circle called WALDEYER which includes:

1-superiorly:the nasopharyngeal tonsil at the roof and the posterior wall of the nasopharynx.

2-inferiorly: the lingual tonsil on the dorsum of the posterior third of the tongue

3-laterally: the palatine tonsils

drainage : efferent lymphatics from the Waldeyer ring drain into the upper deep cervical lymph nodes.

2-lymph nodes of the head and neck

(a)        superficial circular group

(b)       deep circular group

(c)        vertical chain inbetween the 2 circular group

these groups drain the superficial and the deep structures of the head and neck

the superficial and the deep circular groups drain into the vertical group which is called the deep cervical lymph nodes lying alongside the inf. Vena cava deep to the sternomastoid muscle.

(a)       the superficial circular lymph nodes of the head

Lymph nodes	Site	Area drained	Efferent lymphatics pass to
Occipital L.N	Occipital artery	1-post. Part of the scalp 2-the back of the neck	Upper deep cervical L.N
Post. Auricular L.N	Post.auricular vessels behind the auricle	1-post. Part of the scalp 2-auricle 3-external auditory meatus	Upper deep cervical L.N
Parotid L.N	Superficial to the parotid gland	1-temporal region 2-auricle 3-upper 1/2 of the face & eye lids	Upper deep and superficial cervical L.N
Buccal L.N	Facial vessels On the buccinator and the mandible	1-the cheeks 2-the lips	Submandibular L.N