EYE .(organ of vision).
CORNEA (=
CO).
NO blood VESSELs in CO. Thus, after transplantation of cornea
rejection of it does
NOT happen On cross section
CO has
5 layers:
-
Anterior EPITHELIUM. It is – stratified squamous NONkeratinized,
-
Bowmans membrane,
-
Substantia proria (or corneal STROMA). It is occupied 90% of cornea. It is composed of CONNECTIVE tissue LAMELLAE (or PLATES). One LAMELLA is composed of: a) parallelly arranged COLLAGEN fibrills, b) chondroitin sulfate, c) fibroblasts.
-
Descemets membrane,
-
Posterior EPITHELIUM. It is – simple squamous.
VITREOUS BODY. It is composed of: a) cells (hyalocytes), b) ground substance (too
much of
HYALURONIC acid), c) TRANSPARENT protein
vitrein.
LENS.
NO blood VESSELS in lens. After transplantation of lens
rejection of it does
NOT happen. Main tissue type in LENS is –
EPITHELIUM.
It is presented by cells, named
lens fibres. It are: a)
long (
1 cm), narrow epithelial cs, b) without nucleus, c)It cytoplasm contains TRANSPARENT protein
crystalline.
RETINA.
Main tissue type – is
NERVE tissue.
Additionally – is pigment
EPITHELIUM.
Nerve tissue is presented by
TRIneuronal reflex arch:
1st neuron in arch- is
PHOTORECEPTOR cell.
2nd neuron – is
BIPOLAR neuron.
3rd neuron – is
MULTIPOLAR neuron. It
axons leave retina and
form fibres of optic
nerve.
There are
2 types of
photoreceptor cells: 1)
RODs and 2)
CONs.
Common plan of both structure is same:
Rod and
con are composed of
3 portions:
1)
MODIFIED dendrite, 2) Perikaryon, 3) Axon.
Dendrite is composed of 3 portions: a) OUTER segment, b) connecting stalk, c) inner segment.
If OUTER segment of dendrite is CYLINDER-shaped and contains
1000 complete membrane DISCs, so cell type – is ROD. Discs contain visual pigment. RHODOPSIN.
Funct.of
RODs: it are receptors of
TWIGH LIGHT (
dim light,
NONcolour) vision.
If OUTER segment of dendrite is CONICAL-shaped and is composed of INcomplete membrane
semidiscs, so cell type – is CON. Photopigment IODOPSIN is located in outer segment.
Funct. of CONs: it are receptors of
COLOUR (bright light) vision. Pathology of cons- is hereditary desease DALTONISM (colour blindness).
Commonly, rods and cons transform energy of incoming photons into
nerve impulse with participation of photopigment molecules.
Outer segments of dendrites contact with
pigment epithelium. Funct.: pigment epithelial cs make
PHAGOCYTOSIS of membrane discs and semidiscs of outer segments, providing every day RENEWAL of outer segments.
Embryonic origins: 1) for
neurons of
retina – is INNER layer of
optic CUP, 2) for pigment epithelium – is outer layer of optic CUP. Optic CUP- is double-layered outgrowth of
NEURAL TUBE, 3) for epithelium of LENS – is lens placode (derivative of surface ECTODERM). 4) for corneal stroma, vitreous body, sclera, tunica vasculosa (including iris) – is mesenchyme.
Organ of taste – is TASTE BUD (=TB).
TB – is
oval-shaped association of
epithelial sensory cells in epithelium, covering lingual papillae.
TB contains
3 types of
epithelial cells: 1) DARK sensory cs, 2) LIGHT sensory cs. Both types – are tall columnar cs with apical MICROVILLI, protruding into taste pore. Funct.: is taste perception.
Basal surface of both types forms synaptic junction with afferent nerve fibres. 3) BASAL cs – are short cs. Funct.: is origin for regeneration of dark and light cs after it death.
Составитель – доцент В.В. Бондаренко.