The choroid

how many tunics in the eye and what are they

3

fibrous tunic

retinal tunic

uveal tunic

what tunic is the choroid a part of

uveal tunic

largest structure in the uveal layer / vascular layer

choroid

why is uveal layer referred to as vascular layer sometimes

composed mainly of the choroid, which itself is composed mainly of blood vessels

describe the anterior and posterior borders of the choroid

anterior = ORA seratta

posterior = optic nerve (ends here)

(same as retina)

what structures is the choroid between

is sandwiched between the sclera and retina

what are the 2 main structural adaptations of the choroid

highly vascularised (lots of blood vessels)

pigmented

structure related to function: highly vascularised (2)

main blood supply for the retina - providing oxygen and other nutrients

maintenance of ocular temperature

temperature of vascular and avascular regions

vascular - lots of blood vessels - tend to be warm

avascular - cold temperatures

structure related to function - pigmented

prevents stray light reflecting inside the eye

describe blood circulation of the choroid (3)

• most highly vascularised tissue in the eye

• tissue with the highest blood flow in the body

• choroidal circulation accounts for 85% of the total blood flow in the eye

state 2 structural components of the choroid and explain each one

• loose connective tissue containing:

blood vessels; most pf choroid full of blood vessels

loose strands of collagen

fibroblasts = maintain collagen content

• melanin (from melanocytes - release and produce melanin)

found throughout thickness of the choroid

state and explain the 4 main (microscopic) layers of the choroid

• suprachoroidal lamina (lamina fusca)

adjacent to sclera

• choroidal stroma (basement membrane/connective tissue)

large blood vessels (Haller’s layer)

medium blood vessels (Sattler’s layer)

• choriocapillaries

small blood vessels - capillaries of the choroid

specialised capillary bed

densest at the macular area

• Bruch’s membrane

elastic fibres separating retina and choroid

adjacent to the RPE of retina

why is the choriocapilaris densest in the macula

as the macula is avascular - no retinal blood vessels/supply

need a method of supplying blood to this area = via the choriocapillaris

describe the hierarchy of blood vessels in the choroid

• large vessels (Haller’s) branch into…

• medium vessels (Sattler’s) branch into …

• choriocapillaries - capillaries of the choroid