206 SSNS - Histology Flashcards
What are the 3 coats of tunic of the eye?
Fibrous tunic
Vascular tunic
Retinal tunic
What are the pigments in rods & cones?
Rods - rhodopsin
Cones - iodopsin
What are the 2 photoreceptor cells responsible for?
Rods - dim, black & white
Cones - bright, color
What are the 10 layers of the retina? (from inner region to outer region)
Retina layers (from inner region to outer region)
My - Membrane (Inner limiting membrane); (adjacent to vitreous) Nerves - Nerve fibers Get - Ganglions In - Inner plexiform Knots - Inner nuclear Outside - Outer plexiform Our - Outer nuclear Easy - External limiting membrane Practice - Photoreceptors (rods & cones) Review - Retinal pigment epithelium
What’s the Bruch’s membrane & its function?
Innermost layer of choroid
Separates choroid from pigment epithelium
What are the 5 layers of Bruch’s membrane? (from inside to outside)
- The basement membrane of the retinal pigment epithelium
- The inner collagenous zone
- A central band of elastic fibers
- The outer collagenous zone
- The basement membrane of the capillaries
What is the fovea?
A shallow depression in the inner retinal surface, entirely cones, specialized for maximum visual acuity
Located in the center of macula lutea
What is the macula lutea?
A yellowish region surrounding fovea, mainly cones but start to gain rod at the periphery
Ganglion cells & fibers are pushed to the sides to allow light to pass uninterrupted
What are the 5 types of neurons in the retina?
Photoreceptors (rods & cones) Bipolar cells Ganglion cells Horizontal cells Amacrine cells
What are the 2 glial cells found in the retina?
Astrocyte
Müller cells
What are the functions of the retinal pigment epithelium (RPE)?
Light absorption
Production of extracellular matrix
Visual cycle - storage of vit A (precursor of 11-cis retinal) & regeneration of rhodopsin
Phagocytosis of shredded outer segments
Fill in the blanks:
During darkness, receptors are ______.
Depolarized
Fill in the blanks:
During light, receptors are ______.
Hyperpolarized
How do rod bipolar cells communicate with retinal ganglion cells (RGCs)?
They do not contact ganglion cells directly.
Contact amacrine cells which spread out rod info before covering on ganglion cells
How do cone bipolar cells communicate with retinal ganglion cells (RGCs)?
Synapse with RGC directly
What’s the vertical pathway for retinal ganglion cells?
Photoreceptor → bipolar cell → ganglion cell chain
What’s the lateral pathway for retinal ganglion cells?
Photoreceptor → horizontal cell → bipolar cell → amacrine cell → ganglion cell chain
What are the 2 principal types of human retinal ganglion cells?
Midget (Type P) - small receptive field
Parasol (Type M) - large receptive field
What cells are responsible for lateral inhibition?
Horizontal + Amacrine
What are the classical findings in Central Retinal Artery Occlusion?
Cherry red spot, pale optic disc
Pathogenesis of diabetic retinopathy
Capillary basement membrane thickening
Loss of pericytes
Distention of retinal capillary walls
Breakdown of blood-retinal (endothelial) barrier
What is glaucoma due to?
↑ intraocular pressure
Loss of blood flow to the optic nerve
What are the functions of the integumentary system (skin & its appendages)? (4)
Protection
Excretion
Sensation
Secretory
3 main composition of skin & its appendages
Epidermis
Dermis
Hypodermis/subcutis
Epidermal appendages: hair, nail, sweat, oil, mammary glands
5 layers of epidermis (superficial to deep)
“Come Lets Get Some Beers” (from superficial to deep)
Stratum Corneum - outermost; stack of squamous cells w keratin filaments
Stratum Lucidum - no organelles, keratin filaments, eleidin
Stratum Granulosum - keratohyalin granules
Stratum Spinosum - intercellular bridges (desmosomes)
Stratum Basale - innermost, cuboidalcells
Cell types in epidermis (4)
Keratinocytes
Melanocytes
Langerhans cells (dendritic cells)
Merkel’s cells
What is a type of skin determined by?
Thickness of epidermis
Where is thick skin & thin skin found?
Thick: palm & sole
Thin: rest of body
How do thick skin & think skin differ?
Stratum lucidum is absent in thin skin
Thin skin has thin stratum corneum
Where are melanocytes located?
Basal layer of epidermis
What’s the function of melanosomes?
Synthesize & release brown pigment - melanin
How does exposure to UV affect melanin production?
It accelerates the rate of melanin production, to provide a darker color to protect UV damage to cells
What are Langerhans cells?
Tissue-resident macrophages, contains organelles - Birbeck granules
What’s the function of the Birbeck granule?
Uptake of foreign antigens for processing within the lysosomal system before releasing or presenting to T lymphocytes
Langerhans cells derived from?
Monocytes
Where are Langerhans cells found?
All layers of the epidermis of skin, more in stratum spinosum
What are Merkel cells?
Modified epidermal cells in stratum basale - touch receptor
What are the 2 layers of the dermis?
Papillary & Reticular
Where are Meissner’s corpuscles found?
Papillary layer
Dermis of fingertips, soles, nipples, eyelids, lips & genitalia
Where are Pacinian corpuscles found?
Hypodermis layer
Skin of hands & feet
Which layer of dermis contains adipocytes?
Hypodermis/subcutaneous
What’s the function of skin circulation?
Nutrition of skin & appendages
Regulate blood flow to increase or reduce heat loss
What are the 4 skin appendages?
Hair
Sebaceous glands
Sweat glands
Nails
What’s the type of secretory (sebum) mechanism of the sebaceous gland?
Holocrine
What are the 3 modes of secretion?
Merocrine - no part of cell is lost
Apocrine - top of cell lost with secretion
Holocrine - whole-cell detaches with secretion
What is the hardness of the nail dependent on?
Keratin & sulfur
What is skin repair dependent on?
Proliferation of keratinocytes in stratum basale
What are the 4 phases of wound healing?
- Hemostasis
- Inflammation
- Proliferation of granulation
- Remodeling or maturation
