PART IV THE SENSE ORGANS

The visual apparatus receives stimulation of light, and consists of eyeball and accessory apparatus.

Section 1 The Eyeball

The eyeball is embedded in the fat inside the orbit; spherical in shape.

eyeball internal tunic blind part

contents lens

ⅠThe Wall of the Eyeball

It consists of three tunics, viz. external, middle and internal.

Ⅰ）External Tunic(Fibrous Tunic)

1. Cornea: is the anterior 1/6, transparent, and more convex, nonvascular but rich in numerous sensory nerve terminals.

2. Sclera: is the posterior 5/6, white in colour and opaque, pierced by the optic nerve posteriorly.

Ⅱ）Middle Tunic(Vascular Tunic)

This layer contains numerous blood vessels and pigment cells and is brown in colour.

1. Choroid: is the posterior 2/3, and covers the inner surface of the sclera.

2. Ciliay body: lies at the inner surface of the junction of the cornea and the sclera, and consists of the ciliary ring, the ciliary processes and the ciliary muscles. The lens is attached to the inner side of the ciliary processes by the ciliary zonule (suspensory ligaments)

3. Iris: is the most anterior coloured part as a circular perforated disc. Near its centre is a round aperture. named pupil.

Iris divide the space between the cornea and the lens into two parts, anterior and posterior chambers. Iridocorneal angle (angle of anterior chamber) is in anterior chamber, at which the cornea meet with the iris.

Iris contains two sets smooth muscles, sphincter m. of pupil and dilator m. of pupil which are arranged circularly and radially respectively.

Ⅲ）Internal Tunic (Retina)

It may be divided into the optic part, the ciliary part and iridial part. The latter two part are known as the blind part, because of lacking light-sensitive elements.

Ⅱ. The Contents of the Eyeball.

They include the aqueous humor, the vitreous body, and the lens, which are all transparent and avascular, with the cornea altogether form the refractive media. Each plays a part in refracting the light entering the eye.

Ⅰ）Aqueous Humor

It is colourless and transparent water fluid, and fills the chambers of the eye. The circulating route of aqueous humor is as follows.

Secreted by the ciliary bodyposterior chamberpupilanterior chamberiridocorneal anglevenous sinus of scleraanterior ciliary v. the veins of eye.

Ⅱ）Lens

It lies between the iris and the vitreous body. It is a transparent and elastic, biconvex body lacking vessels and nerves.

During near visionhe ciliary m.contractsciliary zonule relaxconvexity of lens increasesindex of refracting increasebringing near objects into sharp focus on retina

Ⅲ）Vitreous Body

It is a transparent, jelly-like substance which fills the space between the lens and the retina.

Section 2 The Accessory Apparatus of the Eyeball

The accessory apparatus of the eyeball includes the eyelid, the conjunctiva, the lacrimal apparatus, the extraocular muscle and the fasciae, the adipose corpus of orbit, et al.

Ⅰ. Eyelids or Palpebrae

Upper eyelid medial canthus

Lower eyelid lateral canthus

From outside inwards, each eyelid includes: skin, subcutaneous tissue, orbicularis oculi m. tarsus and conjunctiva.

Ⅱ. Conjunctiva

It is a thin and transparent mucous membrane.

palpebral conjunctiva

ocular conjunctiva

conjunctival fornices superior conjunctival fornix

Ⅲ. The Lacrimal Apparatus

Ⅰ）Composition and Opening

lacrimal gland-----------------------tears

↓

lacrimal punctum

↓

lacrimal canaliculus

(superior and inferior)

↓

lacrimal passages lacrimal sac

↓

lateral wall of inferior nasal meatus.

1. Lacrimal gland: lies in the lacrimal fossa situated in superolateral portion of orbit.

2. Lacrimal sac: is lodged in the fossa of lacrimal sac situated in the medial wall of the orbit.

Ⅳ. The Extraocular Muscles

Which include the levator palpebral superioris, the four rectus and two oblique muscles.

name action nerve supply

superior rectus turn eye upward, inward Ⅲ inferior rectus turn eye downward, inward Ⅲ medial rectus turn eye inward Ⅲ lateral rectus turn eye outward Ⅵ superior oblique turn eye downward, outward Ⅳ inferior oblique turn eye upward, outward Ⅲ superior palpebral levator elevates upper eyelid Ⅲ

Section 3 The Blood Vessels of the Eye

Ⅰ. The Arteries of the Eye

internal carotid a.

↓

ophthalmic a. superior nasal a.

↓ inferiorior nasal a.

central retinal a.------- superior temporal a. inner layer of retina

inferior temporal a.

Ⅱ. The veins of the Eye

They are two in number, the superior and inferior ophthalmic veins and are devoid of valves.

Chapter 3 The Auditory and Vestibular Apparatus

The auditory and vestibular apparatus is divided into three parts: the external, middle, and internal ears. The external and middle ears are a sound collecting and transmitting apparatus. The internal ear is such an organ that can receive the stimulaton of both sound waves and changes of the position of the head.

external ear external acoustic meatus

tympanic cavity

Section 1 The External Ear

Ⅰ. Auricle: projects from the side 0f the head．Auricular lobule ties below the auricle, and is composed of fibrous and adipose tissue.

Ⅱ. External Acoustic Meatus: extends from the external acoustic porus to tympanic membrane.

The lateral l／3 is cartilaginous, and the medial 2／3 is osseous. It is a curved tube．From outside inwards, first it runs forwards and upwards. then backwards，and finally forwards and downwards.

In childhood, the external acoustic meatus is shorter and more narrow, the tympanic membrane is more horizontal.

Section 2 The Middle Ear

This part is between the external and inner ear.

Ⅰ. Tympanic Cavity

It is an irregular air-filled．space within the temporal bone, and contains auditory ossicles ligaments, muscles, vessels and nerves. It communicates anteriorly with the nasopharynx through the auditory tube, and posteriorly with the mastoid air cells through the mastoid antrum.

Ⅰ）The Wall of the Tympanic Cavity

1. Superior wail (Tegmental wall)

It is a thin plate separating the middle cranial fossa from the tympanic cavity.

2. Inferior wall (Jugular wall)

It separates the tympanic cavity from the jugular fossa.

3. Anterior wall (Carotid wall)

It is close to internal carotid artery. There are two parallel canals on this wall, semicanal for tensor tympani and semicanal for auditory tube.

4. Posterior wail (Mastoid wall)

On the upper part, here is an opening of mastoid antrum, which passes to mastoid air cells through mastoid antrum, On the lower part, the pyramidal eminence and prominence of facial canal exist.

5. Lateral wail (Membranous wall)

It is almost entirely formed by the tympanic membrane, only the superior part of this wall is formed by the lateral wall of the epitympanic recess.

Tympanic membrane is oval and semi-transparent, lies obliquely between tympanic cavity and external acoustic meatus. Umbo is formed by the traction of the terminal point of the handle of the malleus. It also has two parts:

flaccid part: upper 1/4

tense part: lower 3/4, cone of light

6. Medial wall (labyrinthine wall)

It is the lateral wall of the inner ear.

promontory: on the middle of this wall.

vestibular window: posterosuperior to promontory.

(fenestra ovalis)

cochlear window: posteroinferior to promontory, closed by the secondary

(fenestra rotunda) tympanic membrane in vivo

prominence of facial nerve canal: posterosuperior to vestibular window.

Ⅱ）The Auditory Ossicles

The tympanic cavity contains a chain of three ossicles: the malleus incus, and stapes, which connects the tympanic membrane and the fenestra vestibule.

Ⅱ. The Auditory Tube

Lateral1/3--bony partpharyngeal orifice of auditory tubenasopharynx

Medial 2/3--cartilaginous partorifice of tympanic cavity of auditory tubetympanic cavity

The auditory tube is shorter，wider and horizontal in infant, therefore the pharyngeal inflammation may along the auditory tube spread into the tympanic cavity.

Ⅲ. The Mastoid Ant rum and Mastoid Ai r Cells

The mastoid antrum is air-filled space between the tympanic cavity and the mastoid air cells.

Mastoid air cellsmastoid antrumtympanic cavity

(posterior) (middle) (anterior)

Section 3 The Internal Ear

The internal ear lies between the tympanic cavity and the base of the internal acoustic meatus, viz. in the petrous part of the temporal bone.

Osseous labyrinth perilymph

Membranous labyrinth endolymph

Ⅰ. The Osseous Labyrinth

It includes the cochlea, the vestibule and the semicircular canals, from before backwards along the long axis of the petrous part of the temporal body.

Ⅰ）Vestibule

posterior:

Ⅱ）Bony semicircular Canals

ampullar crus(bony ampulla)

anterior semicircular canal

single crus

commune crus

ampullar crus(bony ampulla)

lateral semicircular canal

Ⅲ. Cochlea

It resembles the shell of a snail. It is composed of the bony canal of cochlea winding spirally for 5/2~11/4 turns around the central modiolus which projects the osseous spiral lamina. The bony canal is divided into two parts by this lamina and the basilar membrane of the cochlear duct.

scala vestibule-------upper part

two parts (vestibular scale) communicating through helicotrema

apex and base (cochlear cupula)

Ⅱ. The membranous Labyrinth

It is a series of membranous canal and sacs which lie within the bony labyrinth. From before backwards, it includes: the cochlear duct, the utricle and saccule, and the membranous semicircular ducts.

Ⅰ）The Utricle and Saccule

five opening

utricle

↑ (base)

↓

saccule------anteroinferior part: macula of saccule

--------------------cochlear duct

uniting duct

Ⅱ）The Membranous Semicircular Ducts

They lie within the bony semicircular canal, and are similar to them in shape and names.

On the wall of membranous ampulla, there are the ampular crests which are the organs of kinetic balance.

Ⅲ）The Cochlear Duct

It lies in the bony canal of the cochlea.

A transverse section through the cochlea shows that this canal is divided into three separated channels, namely, the tympanic scale, the vestibular scale and the cochlear duct. The cochlear duct is triangular on the transverse section, and has three walls.

vestibular scale

superior wall: vestibular membrane

cochlear duct

lateral wall: the thickened endosteum

osseous spinal lamina

inferior wall: basilar membrane tympanic scale

(spiral membrane) cochlear duct

The spiral organ is the receptor for auditory sensation, situated on the basilar membrane.

Ⅲ. The Internal Acoustic Meatus.

It is a short canal within the petrous part of the temporal bone.

The nervous system is a master system in the living body, it regulates and intergrates the activities of all the other bodily systems for the benefit of the organism as a whole:

Ⅰ. Subdivision of Nervous System

The nervous system may be divided into the following parts:

telencephalon

brain

central nervous cerebellum midbrain

system﹙CNS﹚ brain stem pons

medulla oblongata

spinal cord

peripheral cranial nerves (12 pairs)

nervous spinal nerves (31 pairs)

system (PNS) visceral sensory n.

visceral n. sympathetic n

visceral motor n.

Ⅱ. The Activity Mode of Nervous System

The functional unit of the nervous system is the reflex arc, a linkage of afferent and efferent neurons

1. receptor

2. afferent n. (sensory n.)

reflex arc 3. center

4. efferent n. (sensory n.)

5. effector

Ⅲ. The Basic Terminology in Nervous System

Ⅰ）Terms in CNS

1. Grey matter----collections of cell bodies and dendrites.

2. White matter----collections of nerve fibres.

3. Cortex----a mantle of grey matter on the brain,such as cerebral cortex.

4. Nucleus----a group of cell bodies which have the same shape and function.

5. Tracts----In white matter, a bundle of nerve fibres which have the same origin, terminaion, passway and function。

Ⅱ）Terms in PNS

1. Ganglion----collections of cell bodies。

2. Nerve----collections of nerve fibres held together by connective tissue sheath。

Chapter 2 The Peripheral Nervous System

The peripheral nervous system ( PNS ) is the nervous structures out-side the brain and spinal cord. It is composed of nerves and ganglia, and usually divided into three portion: ① cranial nerve attaching to the brain. ② spinal nerve attaching to the spinal cord. ③visceral nerve innervating the viscera, heart and vessels, and gland.

Section 1 The Spinal Nerves

There are thiry-one pairs of spinal nerves, each of them arises from two roots attached to the cord, an anerior root (motor fibres ) and a posterior root (sensor fibres). Two roots unite o form the spinal nerve at the intervertebral foramen. The spinal ganglion is an enlargement of the posterior root near the intervertebral foramen.

cervucak n. ----

Spinal n. (31 pair) lumbar n. ----5 pairs

The spinal nerves are mixed nerves which contain two kinds of fibres.

somaic sensory fibres-supplying skin, skele-tal m., tendon and joint.

Sensory nerve fibres visceral sensor fibres-supplying viscera, heart and vessels, and gland.

Motor nerve fibres visceral motor fibres-innervating cardiac m.

smooh m. and gland.

The trunk og spinal nerve is short and gives off two major branches,

anterior ramus

③forming plexus: cervixal, brachial, lumbar and sacralplexuses, except ventral rami of thoracic n.

①smaller mixed n.

posterir ramus ②supplying the skin and muscle of dorsal region of the body

(dorsal ramus) ③segmental distribution

Ⅰ. The Cervical Plexus

Ⅰ）Formation

It is frmed by the anterior rami of the four upper cervical n. (C_1-4).

It is situated deeply in the upper part of the neck, covered by the upper part of the sternocleidomastoid m., and anterior to the levator scapulae and scalenus medius muscles.

Ⅱ）Branches

1. Superficial (cutanous) branches

They emerge near the middle point of the posterior border of the sternocleiddomastoid m. and have a fan-shaped distribution.

lesser occipital n.

2. Deep (muscular) branches

The most important branch of the cervical plexus is phrenic nerve, a mixed nerve.

Anterior rami of cervical n. 3～5phrenic n. laeral border of anterior scalene m.

inlet of thorax

aterior, medial to the m. between subclavian a. and v. -----------------------thoracic cavityin front of the root of lung between pericardium and mediastinal pleuradiaphragm.

Motor fibresdiaphramg

pleurac, pericardium, peritoncum.

Sensory fibres

right phrenic n. liver,gallbadder, and bile duct.

Ⅱ. The Brachial Plexus

Ⅰ）Formation

It is formed by anterior rami of nerver C_5～8 and T₁. It is situated in the supeoposterior side of subclvian a., behind the clavicle, and in axillary fossa.

Five rootsthree trunks (upper, moddle and lower) two divisions (anterior, posterior) three cords (lateral ,medial and posterior) severn important branches.

Ⅱ）Branches

1. Long thoracic n. supplying the anterior seratus m.

2. thoracodorsal n. supplying latissimus dorsi m.

3. Axillary n.

Posterior cordaxillary n. quadrilateral pacewinding round surgical neck of humerusdeep to detoid m.

Muscular branchesdeltoid m., teres minor m.

4. Musculocutaneous n.

Lateral cord musculocutaneous n. piecing coracobrachialis m. between bieceps branchi and branchialis m.

Muscular branches the three m. above.

5. Median n.

Two roots of medial cord and lateral cordembracing axillary a. median n. medial to biceps brachii m. in armcrossing branchial a. cubital fossapiercing pronator teres m.

carpal canal

------------------------wristhand.

Muscular branchesm. in front of forearm except brachioradialis m. flexor carpi ulnaris m. and ulnar half of flexor digitorum pro-fundus m.; m. of thenar eminence except adductor pollicis m. 1～2 lumbricalis m.

Cutanous branchesradial half of palm ;pslmar surface of radial 31／2 fingers.

6. Ulnar n.

Medial cordulnar n. medial to axillary a. piercing medial intermuscular septumback of armulnar grooveforearm, wrist, hand.

flexor carpi ulnaris m.

ulnar half of flexor digitorum profundus m.

muscular branches adductor pollicis m.

hypothenar eminence

interosseous m. (palmar, dorsal)

3～4 lumbricalis m.

cutanous branchesskin on ulnar side of hand;palmar and dorsal surface of ulnar 11/2and 21/2fingers.

7. Radial n.

Posterior cordradial n. behind axillary a. between long and medial head of triceps m.

radial groove lateral superfical branch

---------------------lateral side of arm----------------------------

epicondyle of humberus deep branch

brachiordialis m.

Muscular branches

extensors of arm and forearm.

skin on dorsal surface of arm and forearm

Cutaneous branches

skin on dorsal surface of lateral half of hand and lateral 21/2

Ⅱ. The Ventral Rami of the Thoracic Nervers

They are twelve pairs: the uuper eleven are called intercosal n., which pass into intercosal space and run between internal and exteral intercostals m. along costal groove; the twelfth is called subcostal n. They supply muscles and skin of the thoracic and abdominal wall.

The distribution of the anterior branches of the thoracic nerves is segmental. On the anterior surface of trunk, they present about the level of:

T₂——the sternal angle

T₄——the nipple

T₆——the xiohoid process

T₈——the costal arch

T₁₀——the umbilicus

T₁₂——the midpoint between umbilicus and symphysis pubis (or anterior superior iliac spine)

Ⅳ. The lumbar Plexus

Ⅰ）Formation

It is derived from anterior rami of nerver T₁₂, L_1-4 and coverd by the psoas major m.