Periorbita and orbital fibroadipose tissue

Question 1

What is the volume of each orbital cavity?

Answer 1

30cm³

Question 2

What binds together and supports the orbital contents?

Answer 2

fibroadipose tissue

Question 3

What are 5 separate components into which the orbital contents can be divided?

Answer 3

1. Periorbita
2. Bulbar fascia (Tenon’s capsule)
3. Muscular fascial sheaths
4. Medial and lateral check ligaments
5. Suspensory ligament (of Lockwood)

Question 4

What is another term for the periorbita?

Answer 4

periosteum of the orbit

Question 5

What is the periorbita?

Answer 5

layer of connective tissue tightly bound to the bones only at the sutures, fissures and foraminae in the orbital walls

Question 6

What are the 2 layers that the periorbita is frequently described as having?

Answer 6

1. Dense outer layer
2. Looser inner layer

Question 7

What 2 structures are invested by the looser inner layer of the periorbita?

Answer 7

1. Orbital nerves
2. Lacrimal gland

Question 8

What are the 4 places where the periorbita is tightly bound to the bones?

Answer 8

1. Sutures
2. Fissures
3. Foraminae
4. Posterior lacrimal crest - covers lacrimal sac and is continuous with the fibrous lining of the nasolacrimal duct

Question 9

What is the connection between the periorbita and the lacrimal sac?

Answer 9

the periorbita is tightly bound to the posterior lacrimal crest where it covers the lacrimal sac and is continuous with the fibrous lining of the nasolacrimal duct

Question 10

What is the periorbita like at the inferior and superior orbital fissures?

Answer 10

it forms a dense membrane over them, with sufficient gaps for transmission of nerves and vessels

Question 11

What 3 structures is the periorbita continuous with?

Answer 11

1. the periosteum lining the optic foramen
2. the sheath of the optic nerve, itself an extension of the dura mater of the brain
3. the orbital septum (palebral fascia) in the eyelids anteriorly

Question 12

Where is the periorbita attached anteriorly?

Answer 12

at the orbital margins, becomes continuous with the orbital septum (palpebral fascia) in the eyelids

Question 13

What structure is the periorbita continuous with anteriorly?

Answer 13

orbital septum (palpebral fascia) in the eyelids

Question 14

What is the bulbar fascia (Tenon’s capsule)?

Answer 14

thick fibrous sheath enclosing the globe but separated from it by a layer of loose connective tissue

Question 15

What are the muscular fascial sheaths?

Answer 15

surround the extraocular muscles and blend with the bulbar fascia

Question 16

Label the folowing on the image: periorbita, bulbar fascia, muscular fascial sheaths, medial and lateral check ligaments, suspensory ligament (of Lockwood)

Answer 16

Question 17

What connects the four rectus muscles?

Answer 17

fibrous intermuscular membrane (common muscle sheath)

Question 18

What space is created by the fibrous intermuscular membrane connecting the four rectus muscles?

Answer 18

intraconal space

Question 19

Where is the intraconal space best developed, and where is it incomplete?

Answer 19

best developed in anterior part of orbit

incomplete behind the globe

Question 20

What exists besides the ‘check’ ligaments and where?

Answer 20

other specific attachments via fibrous bands to the orbital walls throughout their course

Question 21

What is the ‘active pulley hypothesis’?

Answer 21

postulates a crucial role for connective tissue bands (including check ligaments) that provide attachments via fibrous bands to the orbital walls;

they are known as ‘pulley suspensions’ and concerns understanding the kinematics of extraocular muscle action

Question 22

Where do the suspensions of check ligaments and other connective tissue bands pass?

Answer 22

between the orbital wall and the ‘pulley sleeve’ of each muscle, which is described as a ring-like extension of the connective tissue from Tenon’s capsule posteriorly around the muscle

Question 23

What controls the tone of the pulleys concerned in the active pulley hypothesis?

Answer 23

possibly under neuronal control because of the presence of smooth muscle fibres

Question 24

What does the active pulley hypopthesis propose?

Answer 24

that the rectus muscles have an orbital layer of muscle fibres that are continuous with (or ‘blend with’ or ‘insert into’) the pulley sleeves (and thus also into the pulley suspensions), in essence one part of a bifid insertion

the inner half or global layer of the rectus muscle continues through the sleeve and bulbar fascia to insert directly into the sclera

newly postulated function for orbital connective tissue: dual insertion allows pulleys to act as a second origin and influence direction of pull of EOMs

Question 25

Where does smooth muscle exist in the periorbita?

Answer 25

within the orbital connective tissue including sleeves of some of the recti muscles

Question 26

What is a suggested function of the smooth muscle in the recti muscle sleeves?

Answer 26

functions, besides superior and inferior palpebral muscles, are currently unclear

Question 27

What has been suggested that the smooth muscle covering of the inferior orbital fissure may represent?

Answer 27

redundant evolutionary remnant

Question 28

What are alternative names for the smooth muscle covering of the inferior orbital fissure?

Answer 28

orbitalis or Müller’s muscle

Question 29

What structures support veins passing through the orbit?

Answer 29

connective tissue septae

Question 30

What structures support arteries passing through the orbit?

Answer 30

travel among fat locules and frequently pierce the septae

Question 31

What connects the superior rectus and the levator palpebrae superioris?

Answer 31

a thickened band of orbital fibrous tissue

Question 32

What is a function of the orbital fibrous tissue connecting the superior retus muscle and the levator palpebrae superioris?

Answer 32

aids in coordinating lifting of the eyelid when the eye is directed upwards by the superior rectus

Question 33

What may the complex and interlinked nature of the fibroadipose system of connective tissue septae explain?

Answer 33

why patients with orbital floor ‘blow-out’ fractures display vertical ocular mobility problems - it is not necessary to invoke the incarcerbation of the inferior rectus and inferior oblique muscles in the fracture to explain the symptoms

Question 34

What 4 things together form the suspensory ligament of Lockwood?

Answer 34

1. medial check ligament
2. lateral check ligament
3. sheath of inferior rectus
4. sheath of inferior oblique