Block 37

Question 1

First and second Pharyngeal arches

Answer 1

The first pharyngeal arch is associated with CN V. It bony derivatives include the maxilla, zygoma, mandible, incus and malleus, its muscular derivatives include masseter and temporalis.
Second pharyngeal arch is associated with CN VII, give rise to stylod process of temporal bone, lesser horn of hyoid (the greater derived from 3rd) and stapes.

Question 2

Tracher collins syndrome

Answer 2

Genetic disorder resulting in abnormal development of 1st and 2nd pharyngeal arches.
-craniofacial abnormalities and often result in airway compromise and feeding difficulties. In addition absent or abnormal ossicles lead to profound conductive hearing loss.

Question 3

Large PDA

Answer 3

-they can present anytime during childhood with progressive pulmonary hypertension and reversal of the shunt to right to left.
-the characterestic continous murmur decreases as the pulmonary pressure rises and ultimately disappears.
Typical consequence include HF and eisenmenger syndrome.
-the cyanosis and clubbing are most pronounced in the lower extremities because PDA delivers unoxygeneated blood distal to subclavian artery.

Question 4

Proximal tubular cell ballobning and vacuolar degeneration , presence of oxalate crystals

Answer 4

• the presence of oxalate crystals in the tubular lumen is highly suggestive of ethylene glycol poisoning.
• its rapidly absorbed from the GI tract and metabolized to glycolic acid which is toxic to renal tubules.
• patients initially manifests with toms of ethanol intoxication, signs of AKI develops about 24-72 hours later with high anion gap metabolic acidosis and osmolar gap also typically seen.

Question 5

Liquefactive necrosis is seen in

Answer 5

• focal bacterial infections that stimulate massive leukocytes
• CNS infarcts due to the lack of substantive supporting stroma.

Question 6

Train of four stimulation

Answer 6

-its used during anesthesia to asses the degree of paralysis induced by NMJ blocking agents.
-PNS is stimulated 4 times in quick succession and muscular response is recorded.
The highest of each bar represent the strength of each twitch, higher bars indicaties activation of increasing numbers of individual muscle fibers.
-nondepolarizing NMJ blocker such as vecuronium leads to progressive reduction in each of the 4 responses, fading pattern as a result of less Ach being released.
-depolarizing blockers such as succinylcholine initially function by preventing repolariztion of motor endplate and show equal reduction of all 4 twitches during TOF stimulation.

Question 7

Succinylcholine

Answer 7

Commonly administred for rapid sequence intubation due to the rapid onset. The duration of action is determined by its metabolism by plasma cholinesterase and is typically <10 minutes.
-however some patients are homozygous for an atypical plasma cholinesterase —> in these patients blockage might perisit for hours and mechanical ventilation is necessary.

Question 8

PE leads to which acid base disorders

Answer 8

PE causes hypoperfusion of affected parenchyma —> V/Q mismatch —>hypoxemia stimulate respiratory drive —> hyperventilation (whoch cant significantly improve blood oxygeneation) —> it decreases CO2 —> respiratory alkalosis with normal bicarbonate levels in the first 48 hours (no compensation).

Question 9

Sternous exercise changes

Answer 9

Increase oxidative metabolsim of glucose and FA in skeletal muscle —>muscle increase their rate of O2 consumption and CO2 production.
-these increase are balanced by increases of the cardiac output/skeletal muscle perfusion and ventilation, respectively.
Homeostatic mechanisms maintain arterial O2 and CO2 contents and arterial PH near normal resting valeus, but there are significant changes in venous blood O2 and CO2 and PH.

Question 10

Small cell lung carcinoma stains

Answer 10

Show evidence of neuroendocrine differentiation. These tumors stain for neuroendocrine markers such as neural cell adhesion molecules (NCAM (CD65)), neuron specifc enolase , chromogranin and synaptophysin.
Some small cell carcinoma express neurofilaments.

Question 11

Nephrotic syndrome pathogenesis in edema

Answer 11

2 mechanisms , underfilling and overfilling contribute to the pathogenesis of edeme in nephrotic syndrome
The underfilling mechanism is particulary significant in minimal change disease in children and presents as follows:
1. Increased glomelular capillary permability to plasma proteins leading to loss of protein in urine
2. The large decrease in serum albumin causes a drop in intravascular oncotic pressure which results in fluid moving into the interstitial space and edema formation
3. The fluid shift results in intravascular volume depletion which triggers the RAAS system to increase aldosterone synthesis and ADH secretion. The result is intavascular sodium and water retention.
The fluid leaks back out into the interstitial space due to the low oncotic pressure exacerbating the edema.
4. Low intravascular oncotic pressure stimulates increased in lipoprotein production in the liver. Impaired catabolism due to decreased LPL and abnormal transport of circulating lipid particles leads to hyperlipidemia

Question 12

Clamydia - lemphogranuloma venorum (LGV)

Answer 12

Serotypes A-C causes ocular infection (trachoma ) in children
Serotype D-K causes urogenital infections and inclusion conjunctivitis
L1-L3 causes lymphogranuloma venereum.
LVG charactrized initially by painless ,small shallow genital ulcer containing infected cells.
-painless nature helps distinguish LGV from other disease.
-the appearance of the ulcer is followed weeks later by swollen, painful, coalescing inguinal nodes (“buboes”) that can develop stellate abscess and rupture.
-if left untreated LGV can cause fibrosis, lymphatic obstuction and anogenital strictures and fistulas.
-histology shows contain areas of mixed granulomatous and neurophilic inflammation with intracytoplasmic chlamydial inclusion bodies in epithelial and inflammatory cells.
-Tx doxycycline.

Question 13

Beta blockers effect on kidney (atenelol)

Answer 13

• at low doses atenolol is a selective B1 Adrenergic antagonist.ß1 receptors are found in cardiac tissue and on renal juxtaglomelular cells, but not in vascular smooth muscle.
• ß1 receptor is a G protein coupled receptor associated with Gs which increases intracellular cAMP levels. Blockade of the ß1 receptors leads to decreased cAMP levels in cardiac and renal tissue without significantly affecting cAMP levels in vascular smooth muscle.
• GPCRs comprise a large family of 7 transmembrane domain receptors that activates intracellular second messenger system involving GPCRs:
  1. CAMP signaling pathway: the activated Gs a subunit activates the enzyme adenylyl cyclase which catalyzes the conversion of ATP into cAMP. Elevated cAMP leads to the activation of protein kinase A. Conversely, the Hi a subunit inhibit adenylyl cyclase therby reducing cAMP.
  2. Phosphatidylinostiol signaling pathway: the activated Gq a subunit activates phospholipase C which degrades membrane lipids into DAG and IP3. Protein kinase C is activated by DAG, and Ca+ is released from SR under the influence of IP3.

Question 14

Osteomyelitis hematogenous spread

Answer 14

• Presenting symptoms are vague and a high index of suspicion is required to make the diagnosing.
• initial symptoms such as malaise and fevers are non-specific.
• as the infection progress, infants and younger children may refuse to move the affected extremity.
• older children complain of pain over a long bone.
• bone pain develops as the abscess expands within the bone, leading to bone necrosis periosteal disruption and swelling of the surrounding soft tissue.
• s.aureus is implicated in most cases of acute hematogenous osteomyelitis in otherwise healthy children.

Question 15

C.difficile colitis pathogenesis

Answer 15

Disruption of intestinal flora.

• toxina A and toxin B (cytotoxin) act synergistically in c.difficle colitis pathogenesis. Toxin inactivates Rho regulatory proteins involved in signal transduction and actin cytoskeletal structure maintenance.
• as a result the toxin cause disruption of intercellular tight junction leading to cell rounding/reaction as well as increased intestinal fluid secretion.

Question 16

Syringomyelia presenting symptoms and area of lesion

Answer 16

• disproprtionate loss of pain and temperature sensation (dissociated anesthesisa) involving the arms and hands.
• the area most commonly damaged are the ventral white commisure and ventral horns.
• the ventral white commisure is located just anterior to the grey commisure, its the area of desucssation for the fibers of the lateral spinothalamic tract. The axons of the second order neurons decussate in the ventral white commissure and ascend in the contralateral lateral funiculus.
• destruction of the ventral white commisure leads to loss of pain and temperature sensation bilaterally over affected dermatmes.

Question 17

Thiazides in preventing Ca stones

Answer 17

Thiazide reabsorbs Ca in the DCT —> less Ca in urine —> no stone formation.

Question 18

Normal pressure hydrocephalus

Answer 18

• decrease CSF rsorption by arachnoid granulation (communicating).
• as CSF accumulates the ventricles expands to accomodate increasing volume.
• symptoms are progressive and include. Gait difficulties appear early, consist of slow short steps with decreased height.
• UMN may also be evident
• coginitive disturbances may arise
• urinary incontinence is late manifestation (urge) reflecting decreased inhibitory control of bladder contraction by frontal love.
• improvement of clinical symptoms in response to CSF removal is diagnostic .
• difference of ex vacuo (seen in alzehiemer disease is the ventricles in ex vacuo stays in proportion of ventricles)

Question 19

Peau d’orange

Answer 19

• generalized erythmatous ras that is often itchy
• skin texture is firm and coarse similar to that of orange peel.
• this is characterestic presentation of inflammatory breast cancer, a poorly differentiated malignancy with unfavorable prognosis.
• its due to cancerous cells obstructing lymphatic drainage after spread to dermal lymphatic spaces.
• due to erythema and diffuse edema, peau d’orange can be mistaken for mastitis, although lack of fever confirms the diagnosis.

Question 20

Varicose veins

Answer 20

Dilated, tortorus veins that predominanyely involve supericial veins of the leg. Many risk factors for varicose veins relate to chronically increased lower extremity venous pressure, long periods of standing, age >50 y.o obesity and multiparity.

• prolonged increased in intraluminal pressure —> venous dilation —> streching of vein causing failure.
• resulting backflow of blood excacerbates the venous hypertension —> precipitating a vicious cycle that leads to further valvular incompetence.
• the end result is venous stasis/congestion with varying degree of edema.
• common complications include painful thromboses, stasis, skin ulceration, poor wound healing and superficial infections.

Question 21

Ovarian cancer protective factors

Answer 21

• combined oral contraceptive
• multiparity
• breastfeeding
• salpingo-oophorectomy.

Question 22

Beta blockers effect on thyroid hormones

Answer 22

Hyperadrenergic manifestation in severe thyrotoxicosis reflects a generalized increased sensitivity to catecholamines via thyroid hormone mediated upregulation of beta adrenergic receptor expression.

• therefore propronalol will reduce HR and anexiety and agitation feeling
• it also decreases the peripheral conversion of T4 to T3 by inhibiting iodothyrodine deiodinase.

Question 23

Lithium/thiazide combination toxicity

Answer 23

• lithium is similar to sodium in its proprties and is almost exclusively secreted in kidney. Like sodium its filtered and reabsorbed mostly in PCT.
• any cause of decrease GFR can increase sodium/lithium reabsorption and lead to increase lithium retention thus toxicity.
• thiazide diuretics limit sodium reabsorption in the distal tubules causing volume depletion and hyponatremia —> PCT stimulated to compensate by reabsorption of Na/lithium —> lithium toxicity.
• ACE and NSAID can also impair lithium clearance and lead to toxicity.

Question 24

Aortic dissection types

Answer 24

Stanford type A referes to dissection that involve any part of the ascending aorta
Stanford type B refers to all other dissection involving the descending aorta.(dissection flap is usually present near subclavian artery -left)

Question 25

Rasburicase in TLS

Answer 25

Its given in tumor lysis syndrome, its mechanism is by converting uric acid into more soluble metabolite. (Uric acid —

Question 26

A1 antrtyrpsin leads to in alveoli

Answer 26

Interalveolar septa destruction

Question 27

Xeroderma pigmentosum

Answer 27

AR, defects in nucleotide excision repair. | Deficiency in exision “endo”nuclease.

Question 28

3’—>5’ exonuclease activity is mutated in

Answer 28

Hereditary nonpolyposis colon cancer

Question 29

Why is tazobactam is added to piperacillin

Answer 29

To prevent destruction of drug by bacteria

Question 30

Dany walker malformation.

Answer 30

Developmental delay charactrized by hypoplasia/absence of the cerbellar vermis and cystic dilation of fourth ventricle with posterior fossa enlargment. - pts presents often during infancy with developmental delay and progressive skull enlargment. - cerbellar dysfunction can result in unsteadiness and impaired muscle coordination. - non communicating hydrocephalus may occur due to atresia of foramina of luschka and magendie resulting in symptoms of elevated cranial pressure. - other associated features can include agenesis of corpus callosum and malformation in face,heart and limbs.

Question 31

Repetitive motor nerve stimulation in lambart eaton leads to

Answer 31

Remarkable increase in muscle response, unlike mesthynia where no response is seen

Question 32

Posterior dudenal wall rupture can lead to hemorrhage to

Answer 32

Gastrodudenal artery

Question 33

Pudendal nerve injury

Answer 33

- it originates from S2-S4 and passes between piriformis and coccygeus muscles as it exit pelvis from greater sciatic foramen. - motor branches innervate the pelvic floor muscles as well as the external urethral and anal sphincters. - the pudendal nerve is vulnerable to strech injury due to its curved course around the ischial spine. - active pushing during prolonged second stage labor places excess stress on the pelvicc floor creating tension on pudendal nerve leading to injury. - injury may lead to fecal incontinence, urinary incontinence, perianal pain and sexual dysfunction.

Question 34

Regulation of glycogenolysis in muscle

Answer 34

In liver phophorylase kinase (responsible for phosphorylation of glycogen phosphorylase-activation)(PK) is activated primarily by epinephrine and glucagon binding to Gs —> increase cAMP concentration and causes phosphorylation of PK. - in skeletal muscle, glucagon receptors are absent, however epinephrine can still phosphorylate PK, however, increased in intracellular Ca+ is more powerful activator of PK. - release of Sarcoplasmic calcium stores following neuromuscular actylcholine stimulation allows for synchronization of skeletal muscle contraction and glycogen breakdown providing the energy necessary for anaerboic muscle contraction.

Question 35

Inhibition of krebs cycle by ethanol

Answer 35

1. Pts with chronic alcoholism are frequently deficieny in thiamine, a necessary cofactor for pyruvate dehydrogenase, a-ketoglutarate dehydrogenase. 2. The metabolism of ethanol by alcohol dehydrogenease and aldehyde dehydrogenase consumes all NAD+, as a result increased NADH inhibit citric acid cycle that needs NAD+ (most commonly a-ketoglutarate dehydrogenease complex)