Sensory System

Lecture for medical students

Part 1 (organ of smell, eye)

Department of histology,cytology and embryology KhNMU

Sensory Systems

1.Sensory Organs2. Nerves

3. Brain Centers (Analyzers)

33 types of Sensory Organs:

1. Primary, Nerve-sensory (Olfactory,

Visual) 2. Secondary, Sensoepithelial

(Taste,Equilibrium,

Hearing)

3. Sensory Nerve Endings

Organ of Olfaction (Smell)

is located in the mucous membrane of the upper and middle nasal

conchae,

Consists of:1. Supporting cells2. Basal cells

3. Olfactory cells having cilia and

axons, forming nerve

Cilia of olfactory cells are irritated by odorous substances.

Under the epithelium locate Bowman's glands producing solvents

increase the concentration of odoriferous substances.

Organ develops from olfactory dimple arising from first brain

vesicle

Organ of olfaction gets 10000 smells,

1000 genes are responsible for smell

• It is the most ancient sensory organ

• Wet weather increases smell

• Without this organ a person becomes anxious

• Smell of lavender keeps anxiety away

The Eye. Visual organ

＊ the complex photoreceptor organ＊ fibrous tunic

(corneoscleral) the wall contains vascular tunic (uvea)

neural tunic (retina)

eyeball contents: lens, vitreous body, aqueous humor accessory structures: eyelids, conjunctiva,

glands

Optic Nerve

Cornea

ScleraRetina

Uvea

I. Fibrous tunic ： has two main portions

sclera: dense regular connective tissue

cornea: contains 5 layers: outer corneal epithelium Bowman's membrane

stroma Membrane of Descemet

endothelium

Cornea

contains free nerve endings

permeable,avascular, transparent

transplantation

II. Uvea – loose c.t., 3 parts:

• 1. Choroid – is nutritive CT, contains capillaries, melanocytes, continuous to:

• 2. Ciliary body is a CT belt, contains muscles, continues to ligament, keeping the lens, changes its shape

• and to• 3. Iris CT contains muscles reduce or dilate

pupil at its center

Pupil

Lens

Iris

Ciliary Body

Optic Nerve

Cornea

ScleraRetina

Choroid

LIMBUS is the junction between sclera and cornea

• Iris constrictor,

dilator muscles regulate pupil

• Ciliary body muscles relax the lens, keeping by suspensory ligament

Iris

Ciliary body

Suspensory ligament

• Anterior chamber – behind the cornea

• Posterior chamber – behind the iris

• Aqueous humor of chambers is produced by ciliary body epithelium

• (Glaucoma)output through venous

sinus to canal of Schlemm

• Lens

Anterior chamber

• LENS is transperent elastic body, covered by flattened epithelium, consists of fibers

• VITREOUS BODY is transperent, colorless, contains 99% of water, hyaluronic acid, collagen

Pupil

LensIris

Ciliary Body

Optic Nerve

VitreousBody

Cornea

ScleraRetina

Choroid

III. Retina

• chain of 3 neurons:

layer of visual cells (rods and cones) – outer nuclear,

layer of bipolar cells – inner nuclear,

layer of ganglionic cells.

10 layers of nerve cells and their processes:

pigment cells (outermost)

Contains 2 sheaths

9 layers of n.cells and processes

Optic Nerve

Ora serrata

Cornea

Sclera

Retina

Choroid

Sclera

Muscles

Choroid

Retina

Sclera

Choroid

Pigment epith..

Inner nuc.

Ganglionic l.

Outer nu.

Ganglionic layer

Inner nuclear layer

Outer nuclear layer

Pigment epithelium

Pigment epithelium

1098

7

6

5

4

32

1

III

II

I

Ultrastructure of rod and cone cells Rod Cone

Outer slender conical, wider segment cylinder shorter

Membrane closed opened, continue

Limiting to cell membrane

disks

Visual rhodopsin iodopsin pigment Sensitive to black, white blue, green, red lights twilight vision (krok)

Cone Rod Rod Cone

The way of light waves

• Through the cornea

• Anterior chamber

• Pupil

• Posterior chamber

• Lens

• Vitreous body

• Through all layers of the retina to rods and cones

Sclera

Choroid

Pigment epith..

Inner nuc.

Ganglionic l.

Outer nu.

Ganglionic layer

Inner nuclear layer

Outer nuclear layer

Pigment epithelium

Optic Nerve (blind macula)

• is made of axons of ganglionic cells

Central Fovea (yellow macula)• is the place of the best vision,

• contains the biggest amount of cones,

• the rest layers are displaced

• 3 functional apparatuses of the eye

ChambersLens

Iris- Ciliary body

Optic Nerve (blind m.)

Central Fovea (yellow m.)

Sclera I. Retina is photosensitive

Vitreous body II. Corneadioptric

(refractive) apparatus

III.Iris accomodative

apparatus

Accessory structures:

• Conjunctiva - CT

• Eyelids – loose and elastic connective tissue, muscles, covered by skin epithelium, containing sebaceous glands – Meibomian and Zeis;

and sweat glands – Moll)

• Lacrimal glands

Embryonic development of eye

• Primary brain vesicle Optic vesicle

Optic stalk Optic cup Retina

• Ectoderm Lens placode

Lens vesicle Lens• Ectoderm Outer corneal epithelium

Eyelids• Mesenchyme: rest Cornea, Uvea, Sclera,

Vitreous body

Chapter 9 Eye and Ear

ectoderm

brain vesicle

Optic cup Lens placode

Mesenchyme

Retina

pigment epithelium

Vitreous body

Lens

Optic stalk

Mesenchyme