Lecture 2 - Occular tissue types 1: Intro to the eye and covering epithelia Flashcards
What are the 4 tissue types in the body
- Nervous
- Muscular
- Epithelial
- Connective
Nervous tissue
makes up nervous system and sends electrical messages around body
involves nerve cells - neurones - sensory and motor
in the eye nerve cells are associated with….
cornea ( sensory ) messaged to brain
ciliary body ( motor ) info from brain to muscles
make up most of retinaW
Muscular tissue
movement/ contraction
What is epithelial tissue divided into
- Covering - protection e.g. skin
- Glandular - secretion
Connective tissue
body’s packaging material
How do we see and interpret things
- Photons travel in wavelight motion
- Light hits object - light we see enters eye - reflected
- Turn light energy into electrical signals transmitted along optic nerve
- Brain interprets signals
What are bones of orbit
Hollow structures in which the eyes sit, attached by muscles which move the eye
7 bones
Eyes in our head
What is around bones of orbit
Packaging material - connective tissue
What are the muscles of the eye
- superior rectus - eye moves up
- superior oblique
- medial rectus - eye moves inwards
- lacteral rectus - right eye moves outwards
- inferior oblique
- inferior rectus - moves eye down
What do muscles of eye do
Fix eyes in place
How many rectus muscles
4
How many oblique muscles and what do they do
2
rotate eye
What is melanin
pigment in epithelial cells
Accounts for variation in skin colour
many of epithilia lining inside of eye is pigmented with melanin ….
- absorbs stray light
- improve image quality - black box effect
What is adnexa and what does it consist of
Other stuff not in eye
- extraocular muscles
- eyelids
- conjunctiva
- lacrimal gland
what is conjunctiva
thin membrane, lines back surface of eyelid, exposed bit of sclera
contains goblet cells
what is lacrimal gland
produces bulk of tear film
What happens when you blink
Secrete tear film into conjucitval sac
All secretions spread over eye
Spreads tear film over eye’s exposed surface when we blink
Tears drained over puncta - through holes called lacrimal punctum into lacrimal sac and then nose
What are the three types of muscular tissue
- Skeletal
- Smooth
- Cardiac
Skeletal muscle
- Found attached to skeleton via tendons, or through connective tissue sheet
- Voluntary control - contract and relax - generate force
- Striated
- Forceful and strong
e. g. actin/myosin, extraocular muscles, eyelid muscle - orbiculiris oculi - closes eyelid when it contractsq
Smooth muscle cells
- Found in walls of internal organs, blood vessels and internal muscles of eye
- Involuntary
- Helps to propel and expel liquid within and from the body
- Non - striated
- Slow
- Weak
e,g, muscles of iris and ciliary body
What shape are epithelial cells
Polyhedral - fit together without gaps with strong attachments between adjacent cells
Hexagonal
What can the free apical surface of covering epithelia be
- Smooth/ flat or
- Covered with micrvilli/ folds - increase SA or cillia - made of microtubules - beat and trap mucus
What can the opposite ( basal ) surface of covering epithelia be
Rests on a basement membrane
Part of it secreted by,,,
- epithelial cells
- connective tissue
Properties of epithelial tissue
- Regenerative
- Avascular
- Innervated by both sensory and motor nerve fibres
Summary of covering epithelia
- Regenerative
- Avascular
- Innervated by both sensory and motor nerve fibres
- Rests on a basement membrane
- Joined to each other by series of junctions
- Polyhedral - hexagonal
- Apical surface - cilia/microvilli
What are the classifications of covering epithelia
- Shape of cells
- Number of layers
Shape of epithelial cells classifcation
- Squamous - flat/lying down
- Cuboidal - round
- Columnar - elongated/long/oval
Number of layers epithelial cells classification
- Simple - 1 layer
- Stratified - many layers
What are the 8 types of covering epithelia
- Stratified squamous
- Stratified cuboidal
- Stratified columnar
- Transitional
- Simple squamous
- Simple cuboidal
- Simple columnar
- Pseudostratified
How many layers does cornea have and what are they
5 epithelium - covering epithelium bowmans layer stroma - bulk of cornea descemets membrane endothelium - internal epithelium
is corneal stroma transparent or opaque and why
transparent
due to tightly packed and regularly arranged collagen fibres
What is outer corneal layer known as and where is it located
Corneal epithelium
Front of eye
What type of epithelium is corneal epithelium and why
Stratified squamous
Protects from dirt, eyelids
Found in areas subject to abrasion
What is the outer, acellular, layer of the stratified squamous epithelium composed of?
Dead cells made up of keratin, good for abrasion and waterproof
Where is stratified epithelium found
Cornea - protect eyelids
Transitional epithelium
Cell shape can change
e.g wall of bladder
Summary of stratified epithelia
- Multilayered
- Found in areas subject to abrasion
- e.g. skin - keratinised
Simple epithelia
Single layer, flat cells
Example of simple epithelia and why
corneal endothelium - Simple squamous
Single layer of flat cells = diffuse easily across barrier of minimal thickness
Ideal for areas where exchange of substances is required - allows avascular cornea to exchange substances with aqueous humour
What is corneal endothelium
inner surface of cornea
Other examples of simple squamous - non ocular
- Lining of blood vessels
- Alveoli of lungs
