B&B Histo_Micro Review PDF

12/11/24 Review By your TAs Eye Histology  How we see- 1. Cornea and lens-> capture and focus light 2. Photoreceptors-> detect light intensity & color (make them into electrical impulse) 3. Optic nerve-> carries impulse to the brain There are also 6 muscles to 2 other parts...

12/11/24 Review By your TAs Eye Histology  How we see- 1. Cornea and lens-> capture and focus light 2. Photoreceptors-> detect light intensity & color (make them into electrical impulse) 3. Optic nerve-> carries impulse to the brain There are also 6 muscles to 2 other parts-> move our eyes and adipose - Lens tissues around them - Vitreous body Corneoscleral coat Cornea- transparent and allows light to enter eye Transition zone- “limus”-> where outflow of aqueous humor is IF PROHIBITED= glaucoma Sclera- thick and fibrous- attachment for extrinsic muscles of the eye Vascular Coat - Iris- adjustable diaphragm - Anterior surface= fibroblasts and melanocytes for eye color - Posterior surface= highly pigmented cells - 2 main muscles (size of pupil) - Sphincter pupillae- circular band of SM (decrease when bright light) - Dilator pupillae- think sheet of pigmented mypepithelial cells (increase with dim light)  - Ciliary muscle- contract lens - Processes: secrete aqueous humor, part of blood-aqueous barrier, and secrete and anchor zonular fiber Flow of AH-> ciliary process secretes it (in post. chamber)-> travels through pupil to ant. Chamber -> to scleral venous sinus and exits through canal of schlemm Choroid - Provides nourishment to the retina Lens Retina - Neural retina- light sensitive receptors and neuronal networks - Retinal pigment epithelium (simple cuboidal melanin cells) Know the 10 layers! -mark them by ganglion cells, inner/outer nuclear layer, rods and cones Visual Processing - In the dark- want to increase cGMP to open up more Na+ channels to depolarize - In the light- want to decrease cGMP to close Na+ channels Ear Histology External Ear Middle Ear Internal Ear Auricle collects Air filled spaces Series of and amplifies where air interconnected sounds vibrates are bony-walled converted to chambers and mechanical passages that vibrations processes sound waves Contains hair Contains Contains bony follicles, auditory and sebaceous ossicles, membranous glands, and tympanic labyrinth ceruminous membrane, and glands auditory tube External Ear Inner Ear  Sensory Structures Hair cells: mechanoelectric transducers ○ Covered by gelatinous cupula ○ Contains one kinocilium and multiple shorter stereocilia Ossicle movement → fluid movement → stereocilia movement → electrical signal Sensory Structures Macula: detects changes in head position (linear acceleration) ○ Located in utricle and saccule ○ Contain hair cells covered by otolithic membrane Crista ampullaris: ○ Located in semicircular canals within the ampulla ○ Contain hair cells covered by cupula ○ Connected to vestibular nerve  Sensory Structures Organ of Corti: detects sound and converts the electrical signals so that the brain can interpret them (transduction) ○ Located in the cochlear duct Scala vestibuli and tympani contain perilymph Scala media contains endolymph Use basilar membrane and vestibular membrane as landmarks  1. Sound waves enter the external ear towards the Putting it Together tympanic membrane 2. This causes vibrations of the ossicles 3. The stapes moves against the oval window causing fluid movement in the cochlea 4. Fluid movement causes vibration of the basilar membrane, generating a shearing force of the tectorial membrane 5. Stereocilia moves to open ion channels, causing depolarization 6. These electrical signals are sent to the auditory nerve fibers for higher processing Practice Questions  Eye Infections Bacteria, Viruses, and Parasites Blepharitis - Inflammation of the eyelid - Causative Agent: - Major: S. aureus - Minor: HSV, Varicella, Phthiris pubis - CP: itching, burning, redness, and crusting of lashes - Stye - localized inflammation of eyelid at a hair follicle or sebaceous gland - Due to S. aureus CoAg+ = can wall itself off Adult & Child Conjunctivitis - Inflammation of conjunctiva - CP: vary based on causative agent - Causative Agent: - Infectious: - Bacterial: S. aureus, S. pneumoniae, H. influenzae, M. catarrhalis, N. gonorrhoeae, C. trachomatis - SXM: ACUTE onset - redness, purulent discharge - Tx: Broad Spec Antibiotics (azithromycin & cipro) - Viral: Adenovirus, HSV1, VZV - SXM: subacute onset -redness, clear/watery discharge, pruritus - Non-Infectious: allergens Neonatal Conjunctivitis - inflammation of conjunctiva - CP: affects newborns in the first month of life - Most infectious agents are STI’s - Infection acquired as baby passes through the birthing canal - Causative Agents: - C. trachomatis (D-K) - Inclusion conjunctivitis - SXM: yellowish/mucopurulent discharge 5-12 DAYS AFTER BIRTH - Complications: 20% many develop pneumonia - Tx: erythromycin, macrolides, tetracyclines - N. gonorrhoeae - Ophthalmia neonatorum - SXM: purulent discharge 1-5 DAYS AFTER BIRTH - Complications: blindness, bacteremia, meningitis - Tx: erythromycin or 3rd Gen Cephalosporin if systemic Keratoconjunctivitis - infection of conjunctiva & cornea - Causative Agent: C. Trachomatis A-C - CP: Early follicular keratoconjunctivitis -> corneal abrasions -> re-infection - Infection often starts in conjunctiva and progresses to cornea - Early phase: hand to eye transmission -> eye pain, redness, itching - Eye pain = invaded cornea - Late phase: itching creates corneal abrasions 0> scarring, lid deformities, and blindness - Tx: macrolides, tetracyclines Keratitis - Inflammation of cornea - Most common in individuals with recent eye trauma (i.e. rubbing eyes), or contact lens wearers - CP: acute onset pain, photophobia, blurred vision, redness - Organisms invade stroma -> ulcerations -> immune response - Causative Agents: - Bacteria & Virus: any that cause conjunctivitis - HSV - chronic keratitis - Parasitic: - Acanthamoeba - protozoan - Oncocerca volvulus - helminth - Vision threatening! Class Organism Key Features Infections Bacteria S. aureus ○ G+ cocci ○ Blepharitis ○ Catalase+ Stye ○ CoAg+ ○ conjunctivitis ○ B-hem ○ FBP ○ Protein A ○ A-toxin Bacteria S. pneumoniae ○ G+ diplococci ○ conjunctivitis ○ Catalase - ○ A-hem ○ Optochin sensitive ○ Capsule ○ Autolysins ○ pneumolysin Bacteria H. influenzae ○ G- bacilli ○ Conjunctivitis ○ Unencapsulated ○ Otitis media ○ Grow on chocolate agar ○ URI ○ IgA protease ○ biofilm Bacteria N. Gonorrhoeae ○ G- diplococci ○ Gonorrhea ○ Oxidase + ○ Conjunctivitis ○ Ferment glucose ○ Neonatal conjunctivitis ○ Pili - antigenic variations Phase variations ○ LOS ○ IgA protease ○ Hide in neutrophils Facultative intracellular Bacteria M. catarrhalis ○ G- coccobacilli ○ Conjunctivitis ○ Adhesions ○ Otitis media ○ B-lactamases ○ URI Bacteria C. Trachomatis ○ Weak G- ○ Conjunctivitis A-C: eyes ○ Obligate intracellular ○ Neonatal conjunctivitis D-K: STI Inclusion bodies - replicative L1-L2: LGV Elementary bodies - infectious Virus Adenovirus ○ Ds DNA ○ URI ○ Non-enveloped ○ Conjunctivitis ○ Kerato-conjunctivitis Virus HSV1 ○ Ds DNA ○ Keratitis Linear ○ conjunctivitis ○ enveloped Protozoa Acanthamoeba ○ Water/contact lens ○ Keratitis ○ Trophozoites/cyst ○ Corneal ulcers Helminth Onchocerca volvulus ○ Black fly vector ○ "river blindness" ○ Worms develop in SubQ ○ Form nodules in lymphatics ○ Microfilariae - eggs Ear Infections Otitis Externa- External Ear Infection Localized Infection ○ Hair follicles become irritated→ folliculitis/furunculosis ○ Caused by Staph Aureus Gram (+) cocci, coagulase (+), Protein A Diffuse ○ “Swimmer’s ear” ○ Due to excess moisture and increased pH ○ Presents with itching and pain ○ Caused by Pseudomonas Aeruginosa ○ Treat with ear drops to decrease swelling, usually Fluoroquinolone Pseudomonas Aeruginosa Gram (-) bacilli, aerobic, oxidase (+) Produces pyocyanin ○ Gives it a green/blue color Sweet/grape like odor Opportunist** especially for CF patients Likes moist environments→ water, humidifiers Exotoxin A ○ ADP ribosylation EF2 → blocks protein synthesis→ cell death Acute Otitis Media- Middle Ear Infection Presents with ear pain (otalgia), fever, usually following URI ○ Most common in children- may present with fussiness, rubbing the ear, difficulty sleeping Main Causes ○ Viruses: RSV, influenza virus, rhinovirus ○ Bacteria Streptococcus Pneumoniae Gram (+), encapsulated, bile soluble, alpha hemolytic Haemophilus Influenzae Gram (-), plated on chocolate agar Moraxella Catarrhalis Gram (-), non motile, oxidase (+) Acute Otitis Media- Diagnosis and Treatment Physical Exam ○ Redness, bulging of Tympanic membrane with middle ear effusion Treatment ○ Watchful waiting Depends on the situation- usually if exam doesn’t look bad or if the symptoms aren’t that bad ○ Amoxicillin Standard treatment, typically use if fever or if symptoms persist for more than 2-3 days ○ Augmentin If amoxicillin in the past 30 days- give Augmentin Toxoplasmosis Toxoplasmosis - T. gondii - Opportunistic protozoal CNS infection - Mono- symptoms only in immunocompetent individuals - In Meats and cat feces - 1-2 week incubation period - Infection can be focal or diffuse - Adult Infection: - Related to immunosuppressive state - Associated with the neurologic symptoms in AIDS - Forms multiple grey abscess in deep grey matter - “Ring-enhancing lesions - Fetal/Congenital Infection: - Acquired through maternal infection in utero - Necrotizing CNS lesions - bad - Chorioretinitis, hydrocephalus, calcifications - multifocal - why pregnant women shouldn’t clean the litter box? - Can cross placenta