Анатомия домашних животных неврология = Anatomy of domestic animals Neurology. Учебно-методическое пособие

c.Cerebrifugal (efferent, descending, motional) paths conduct nervous impulses from the brain to the body’s periphery.

Table 6

1.2.The brain

The brain (encephalon) is a continuation of spinal cord and lies in cranium cavity. It consists of gray and white matters, that contain cavities (ventricles) filled with liquor.

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Table 7

Brain

Transverse cerebral fissure divide brain into cerebrum (cerebrum) and rhombencephalon (rhombencephalon). Cerebrum consistsofforebrain(telencephalon),diencephalon(diencephalon) and mesencephalon (mesencephalon), and rhombencephalon – of metencephalon (metencephalon) and medulla oblongata (medulla oblongata).

Table 8

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Spinal cord and the brain are covered by meninges, between which there are fissured spaces filled up with cerebrospinal liquor. It provides good protection of tender brain matter. Spinal cord meninges continue in cerebralmeninges. There are three meninges: external – hard, medial – arachnoid, internal – soft (vascular).

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Hard cerebral meninx consists of dense connective tissue andformspeculiarsacaroundthebrain.Betweenitandperiosteum there is epidural space, that is well defined only in spinal cord and filled in with loose connective tissue with great amount of lipocytes. Two venous sinuses lie ventrally in epidural space, they collect blood from spinal cord and vertebratea.

Arachnoid cerebral meninx is very fragile, thin and transparent,consistsoflooseconnectivetissue.Itisseparatedfrom hard meninx by fissured subdural space, and from soft meninx by subarachnoid space, filled in with liquor. Meninx forms coat around brain and connects with hard meninx by afferent vessels and efferent nerves, with soft meninx – by separate groups of collagen fibers.

Soft (vascular) meninx consists of loose connective tissue and comprises great amount of blood vessels and innervated. It firmly fuses with brain. It has a lot of vascular plexuses.

Table 10

Meninges

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2. PERIPHERAL NERVOUS SYSTEM

2.1Spinal nerves and ganglions

The peripheral nervous system comprises ganglions and nerves with their roots, plexuses and terminations. Ganglion is an accumulation of neurons bodies in the periphery, they are surrounded by neuroglial cells and connective tissue. They are situated along nerves. Nerves is a group of nervous fibers, that are coveredbyconnectivetissuecoat.Accordingtofunctionganglions and nerves are divided into spinal, cranial and vegetative.

Spinal nerves (nervi spinales) start by 2 roots (radix dorsalis et ventralis), branching of spinal cord: dorsal (sensitive) and ventral (motional). Dorsal root has thickening – spinal ganglion (ganglion sinalis), that is formed by sensitive neurons bodies. Both roots fuses into common trunk and give one branch to spinal cord and another to ganglions pf spinal trunk (autonomous nervous system), instead it gets sympatic branch for vessel innervation. Thus, spinal nerve is mixed and comprises sensitive, emotional and sympatic nervous. Spinal nerves are differentiated by topography in cervical, thoracic, lumbar, sacral and caudal.

Cervical spinal nerves (n. cervicales), the 8 pairs of them go through intervertebral foramens and divide into dorsal and ventral branches. Dorsal branches innervate cervical vertebrae, cervical extensors, integument, and ventral branches – cervical flexors, integument and participates in brachial plexus.

Thoracic spinal nerves (n. thoracici). Their number corresponds with the number of thoracic vertebratea. They also divide into dorsal and ventral branches. Dorsal branches innervate thoracic vertebratea, extensors of the vertebral column, dorsal musclesofshoulderjoint,integument.Ventralbranchesparticipate in brachial plexus.

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Table 11

Brachial plexus – plexus bracialis

Lumbar spinal nerves (n. lumbales). Their number corresponds with the number of lumbar vertebratea. Dorsal branches innervate lumbar vertebratea, extensors of the lumbus, skin. Ventral branches participate in lumbar plexus.

Table 12

Lumbar plexus – plexus lumbalis

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Sensitive cranial nerves. Their development associated with development of receptor apparatus and occurrence of sense organs. They are 1,2 and 8 pairs.

Motional cranial nerves. They are formed by motional nerve fibers, that are processes of motional nucleus cells of brainstem. They are 3,4,6,11 and 12 pairs. 3rd, 4th and 6th pairs innervate musculature, originated from tree preauricular segments (premaxillary, submaxillary, subglossal).

Mixed cranial nerves. Their development is closely associated with formation of gill apparatus and primary segmentation of head. They are 5,7,9 and 10 pairs.

I pair - olfactory (n. olfactorii) sensitive; goes from olfactory epithelium of nasal cavity, through cribriform plate of ethmoid to olfactory bulbs (forebrain).

II pair – optical (n. opticus) sensitive; goes from retina, troughopicalcanalintoskullcavity(opticchiasm,opticthalamus).

III pair – oculomotor (n. oculomotoricus) motional; goes from mesencephalon, through orbital fissure to ocular muscles.

IV pair – throchlearis (n. trochlearis) motional; goes from middle ear, through orbital fissure to ocular muscles.

Table 14

V pair – trigeminal (n. trigeminus) – mixed nerve divides into 3 nerves

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VI pair – abductive (n. abducens) motional; goes from medulla oblongata through orbital fissure to eye muscles.

Table 15

VII pair – facial nerve (n. facialis) – mixed nerve, from skull cavity goes through facial canal (petrosal part of temporal bone)

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VIII pair – vestibulocochlear (n. vestibulocochlearis) – sensitive; goes from auricular and equilibria organ in the medulla oblongata.

IX pair – glossopharyngeal (n. glossopharingeus) mixed; goes from the medulla oblongata, through lacerated foramen and innervate muscles of pharynx, taste buds of the tongue and parotid gland.

X pair – vagus (n. vagus) – is relating to vegetative nerve system (mixed nerve).

XI pair – accessorial (n. accessorius) – motional; goes from medulla oblongata, through lacerated foramen and innervates muscles of shoulder girdle.

XII pair – hypoglossal (n. hypoglossus) motional; goes from medulla oblongata, through hypoglossal foramen and innervates muscles pf tongue and hyoid.

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