Medical Topics Quiz

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Questions and Answers

Which statement accurately describes the role of complement C5a in phagocytosis?

C5a binds to receptors on phagocytes and stimulates them. (correct)

C5a directly destroys pathogens by binding to them.

C5a enhances phagocytosis by activating complement C3b.

C5a is involved in the initial recognition of pathogens.

What is the most significant consequence of a folate deficiency?

Enhanced DNA synthesis.

Improved immune response.

Increased erythrocyte production.

Defective nucleic acid synthesis and increased apoptosis. (correct)

What is the primary mechanism by which stimulant medications help manage ADHD?

Blocking dopamine receptors.

Increasing the availability of norepinephrine and dopamine. (correct)

Decreasing serotonin levels in the brain.

Inhibiting norepinephrine degradation.

What is the primary characteristic of vestibular schwannomas?

They lead to ipsilateral hearing loss and facial symptoms. Signup and view all the answers

What is the role of CD-40 ligand in the immune response?

It binds to CD40 on antigen presenting cells to activate them. Signup and view all the answers

Which type of joint structure is associated with intercellular communication?

Gap junctions. Signup and view all the answers

What leads to chronic bronchitis as a primary health issue?

Chronic tobacco smoking. Signup and view all the answers

What is a common result of an incomplete obliteration of the processus vaginalis?

Communicating hydroceles and indirect inguinal hernias. Signup and view all the answers

What causes the initial erythema after a superficial thermal burn?

Release of preformed mediators like histamine from mast cells. Signup and view all the answers

Which condition is characterized by the triad of eczema, thrombocytopenia, and immune deficiency?

Wiskott-Aldrich syndrome. Signup and view all the answers

What is the primary virulence factor of Streptococcus pyogenes?

M protein Signup and view all the answers

What underlying defect is responsible for Ehlers-Danlos syndrome?

Deficient collagen synthesis Signup and view all the answers

What distinguishes acute stress disorder from post-traumatic stress disorder (PTSD)?

Duration of symptoms Signup and view all the answers

In which condition is there a defect in the mitochondrial enzyme involved in the metabolism of tyrosine?

Alkaptonuria Signup and view all the answers

Which method is used for the acute management of gout when NSAIDs are contraindicated?

Colchicine Signup and view all the answers

What is the key characteristic of xeroderma pigmentosum?

Defective nucleotide excision repair Signup and view all the answers

What distinguishes atrial septal defect in terms of its impact on heart sounds?

Wide fixed splitting of S2 Signup and view all the answers

What is a common consequence of excessive ACTH secretion in patients with Cushing syndrome?

Hyperpigmentation Signup and view all the answers

What type of hypersensitivity reaction involves complement activation due to immune complex deposition?

Type III Signup and view all the answers

Which condition is associated with elevated levels of unmeasured acidic compounds?

Diabetic ketoacidosis Signup and view all the answers

What is a consequence of mutations in the TTN gene associated with familial dilated cardiomyopathy?

Decreased contractility of cardiac muscles Signup and view all the answers

Which statement about immunotherapy medications utilizing the Fab domain is true?

They are designed to penetrate tissues deeply. Signup and view all the answers

What characterizes the transformation of osteoblasts into osteocytes?

They retain their location within the extracellular matrix. Signup and view all the answers

What is a result of fractures to specific cranial bones affecting the middle meningeal artery?

Epidural hematoma development Signup and view all the answers

What increases the risk of endometrial carcinoma in patients with PCOS?

Increased estrogen production and chronic anovulation Signup and view all the answers

Which coagulation factors require vitamin K as a cofactor for activation?

Factors 2, 7, 9, 10 Signup and view all the answers

What underlies type IV hypersensitivity reactions like contact dermatitis?

T lymphocyte mediated tissue damage Signup and view all the answers

Which mechanism leads to Hirschsprung disease?

Migration failure of neural crest cells Signup and view all the answers

What genetic alteration is typically found in pancreatic ductal adenocarcinoma?

KRAS mutations Signup and view all the answers

What is characteristic of the presentation of Burkitt lymphoma?

A facial mass Signup and view all the answers

What pathological features are indicative of chronic bronchitis?

Thickened bronchial walls and mucous gland enlargement Signup and view all the answers

Which of the following statements accurately describes the role of cortisol in the adrenal medulla?

Cortisol increases the expression of phenylethanolamine-N-methyltransferase. Signup and view all the answers

What is a defining feature of the blood-testes barrier?

It prevents immune exposure to developing spermatids. Signup and view all the answers

What is the primary effect of ADH hormone on the kidneys?

Increases urea and water reabsorption. Signup and view all the answers

Which type of vasculitis is characterized by IgA deposition and affects the renal system?

Henoch-Schonlein purpura. Signup and view all the answers

In the process of reciprocal induction, which two organs are typically involved?

Kidney and eye. Signup and view all the answers

What type of burn injury typically results in blisters?

Deep thermal burn. Signup and view all the answers

Which condition is caused by an incomplete fusion of the urethral folds in males?

Hypospadias. Signup and view all the answers

Which statement accurately describes megaloblastic anemia due to folate deficiency?

It leads to increased apoptosis of hemopoietic cells. Signup and view all the answers

Which structure in the nephron is involved in the reabsorption of glucose?

Proximal convoluted tubule. Signup and view all the answers

What is the primary consequence of CD40 ligand binding to CD40 on antigen-presenting cells?

It enhances B cell activation. Signup and view all the answers

What is the primary risk factor for endometrial carcinoma in patients with PCOS?

Increased estrogen production Signup and view all the answers

Which characteristic change occurs in osteoblasts as they mature into osteocytes?

Communication through gap junctions Signup and view all the answers

In the context of immunotherapy, what significant limitation exists for medications that utilize only the Fab domain?

Lack of Fc receptor-mediated immune effector functions Signup and view all the answers

Which cell type migrates to regional lymph nodes during allergic contact dermatitis to initiate clonal expansion of T cells?

Langerhans cells Signup and view all the answers

Which mutation is commonly associated with pancreatic ductal adenocarcinoma?

KRAS Signup and view all the answers

What pathological feature is typically associated with chronic bronchitis?

Bronchial wall thickening Signup and view all the answers

What is the expected clinical manifestation in newborns with Hirschsprung disease?

Failure to pass meconium Signup and view all the answers

Which cofactor is essential for the activation of coagulation factors 2, 7, 9, and 10?

Vitamin K Signup and view all the answers

What type of immune response predominantly mediates type IV hypersensitivity reactions?

T lymphocytes Signup and view all the answers

What cranial bone fractures can lead to an epidural hematoma through laceration of the middle meningeal artery?

Temporal and sphenoid bones Signup and view all the answers

What is the clinical manifestation of alkaptonuria due to the accumulation of homogentistic acid?

Black urine and blue-black pigmentation of the face Signup and view all the answers

What characterizes the response of stellate cells during hepatic injury?

Production of collagen as myofibroblasts Signup and view all the answers

Which condition is associated with a deficiency in the enzyme procollagen peptidase?

Ehlers-Danlos syndrome Signup and view all the answers

What primarily leads to the pathological features of lateral epicondylitis?

Overuse of wrist extensor muscles Signup and view all the answers

What distinguishes REM sleep behavior disorder from other sleep disorders?

Loss of atonia during REM sleep Signup and view all the answers

What is the primary virulence factor of streptococcus pyogenes that protects it from phagocytosis?

M protein Signup and view all the answers

Elevated anion gap metabolic acidosis can be caused by all of the following except?

Renal tubular acidosis Signup and view all the answers

Which of the following describes the hypersensitivity mechanism involving immune complexes?

Type III hypersensitivity Signup and view all the answers

What is a clinical feature of gout linked to the mutations in phosphoribosyl pyrophosphate synthetase?

Increased production of purines Signup and view all the answers

Which condition is characterized by the symptoms of mydriasis, abdominal pain, and diarrhea during opioid withdrawal?

Opioid withdrawal syndrome Signup and view all the answers

Study Notes

Familial Dilated Cardiomyopathy

Mutations in the TTN gene, which codes for titin, are commonly associated with familial dilated cardiomyopathy.

Immunotherapy

Fab domains of immunotherapy medications can penetrate tissues more effectively than full antibodies.
The lack of Fc receptors in Fab domains prevents them from triggering cell killing via complement or phagocytosis.

Bone Remodeling

Osteoblasts differentiate into osteocytes.
Osteocytes detect increased mechanical load in bones and communicate through gap junctions to coordinate bone remodeling.

Epidural Hematoma

Fractures involving the frontal, parietal, temporal, and sphenoid bones can lacerate the middle meningeal artery, causing an epidural hematoma.
The middle meningeal artery is a branch of the maxillary artery.

Polycystic Ovarian Syndrome (PCOS)

Patients with PCOS are at increased risk of endometrial carcinoma due to elevated estrogen production and chronic anovulation.

Vitamin K

Vitamin K acts as a cofactor for gamma glutamyl carboxylase, an enzyme responsible for activating coagulation factors 2, 7, 9, and 10 through posttranslational gamma carboxylation.

Type IV Hypersensitivity Reactions

Type IV hypersensitivity reactions, such as Candida extract skin tests and contact dermatitis, are mediated by T lymphocytes.
Allergic contact dermatitis involves Langerhans cells migrating to regional lymph nodes, where they present antigens to naive T cells, leading to clonal expansion.
Upon re-exposure to the hapten, sensitized T cells cause tissue damage, manifesting as pruritic erythema, vesicles, and/or bullae 2-3 days after exposure.

Hirschsprung Disease

Hirschsprung disease arises from abnormal migration of neural crest cells (ganglion cell precursors) during embryogenesis.
The rectum is always affected, resulting in newborn failure to pass meconium.

Pancreatic Ductal Adenocarcinoma

Mutations in the KRAS oncogene are frequently observed in pancreatic ductal adenocarcinoma.

Burkitt Lymphoma

C-Myc, a protooncogene, is overexpressed in Burkitt lymphoma.
This type of lymphoma presents with a facial mass.

Chronic Bronchitis

Chronic bronchitis is characterized by thickened bronchial walls, lymphocytic infiltration, mucous gland enlargement, and patchy squamous metaplasia of the bronchial mucosa.
Tobacco smoking is the primary cause of chronic bronchitis.

Opsonization

IgG and complement C3b are considered the most important opsonins.

Complement C5a

Complement C5a enhances phagocytosis by macrophages by binding to receptors on phagocytes and directly stimulating them.

Neurofibromatosis Type I

Cutaneous neurofibromas, composed of Schwann cells, are present in neurofibromatosis type I.
Schwann cells originate from neural crest cells during embryonic development.

Infective Endocarditis

In intravenous drug users, infective endocarditis commonly affects the tricuspid valve.

Myotonic Dystrophy

Myotonic dystrophy is an autosomal dominant condition caused by a trinucleotide repeat expansion.
Subsequent generations exhibit an increased number of repeats, leading to cognitive impairment and muscle weakness.

Reciprocal Induction

Reciprocal induction is a form of signaling that occurs between two tissues, requiring the presence of both for normal development.
This type of induction is observed in the kidney and eye.

Acid-Fast Stain

Acid-fast staining identifies organisms that possess mycolic acid in their cell walls.

Cortisol

Cortisol enhances the conversion of norepinephrine to epinephrine in the adrenal medulla by increasing the expression of phenylethanolamine-N-methyltransferase.

Atopic Dermatitis

Th2 cytokines, IL-4 and IL-13, stimulate IgE production in atopic dermatitis.

Communicating Hydroceles and Indirect Inguinal Hernias

Incomplete obliteration of the processus vaginalis leads to both communicating hydroceles and indirect inguinal hernias.

Blood-Testis Barrier

Tight junctions between Sertoli cells in the seminiferous tubules form the blood-testis barrier, protecting developing spermatids from immune exposure.

Cranial Nerves and Foramina

Foramen rotundum houses CN V2 (maxillary nerve).
Foramen ovale contains CN V3 (mandibular nerve).
Foramen spinosum accommodates the middle meningeal artery and vein.

Folate Deficiency

Folate deficiency inhibits nucleic acid synthesis, particularly thymidine formation.
This results in defective DNA synthesis and increased apoptosis, affecting hemopoietic cells, leading to megaloblastic anemia.

Antidiuretic Hormone (ADH)

ADH acts on the medullary segment of the collecting duct, enhancing urea and water reabsorption, allowing for the production of maximally concentrated urine.

Henoch-Schönlein Purpura

Henoch-Schönlein purpura is an IgA-mediated, leukocytoclastic vasculitis characterized by palpable purpura, arthralgia/arthritis, abdominal pain, and hematuria.
Renal involvement is caused by mesangial deposition of IgA immune complexes.

Neural Tube Defects (NTDs)

An open NTD allows leakage of alpha-fetoprotein and acetylcholinesterase into the amniotic fluid, resulting in elevated levels detected during amniocentesis.

Superior Mesenteric Artery (SMA) Syndrome

The transverse segment of the duodenum passes through a mesenteric fat pad that provides structural support for the SMA.
Compression of the duodenum by the SMA can cause recurrent bilious vomiting.

Viral Binding to Host Receptors

HIV gp120 binds to CD4.
Epstein-Barr virus gp350 binds to CD21.
Parvovirus B19 binds to the erythrocyte P antigen.

Leukocyte Adhesion and Transmigration

ICAMs mediate neutrophil tight adhesion.
PCAMs facilitate transmigration.

Herpes Simplex Virus (HSV) Infection

HSV infection initially follows a dynein-dependent (retrograde) pathway, followed by a kinesin-dependent (anterograde) pathway.

Ecological Studies

Populations, not individuals, are the units of analysis in ecological studies.
Ecological studies cannot be used to draw conclusions about individuals.

Posttranslational Modification of Proteins

Posttranslational modification of proteins plays a crucial role in directing proteins to their appropriate locations.

Attention Deficit Hyperactivity Disorder (ADHD)

Stimulant medications used for ADHD increase the availability of norepinephrine and dopamine in the prefrontal cortex.

Vestibular Schwannoma

Vestibular schwannomas can cause hearing loss, ipsilateral facial paresthesia, and ipsilateral facial paresis.
They are located at the cerebellopontine angle.

Pheochromocytoma

Pheochromocytoma is a malignancy arising from the chromaffin cells of the adrenal medulla.
The adrenal medulla is derived from neural crest cells.

Thermal Burns

The earliest morphological change observed after a superficial thermal burn is erythema due to the release of preformed mediators, such as histamine, from mast cells.
Deeper burn wounds develop blisters as a result of fluid extravasation through gaps between damaged venule endothelial cells.

Protein A

Protein A, a virulence factor found in the peptidoglycan cell wall of Staphylococcus aureus, binds to the Fc portion of IgG.
This binding impairs complement activation, opsonization, and phagocytosis.

Sjogren Syndrome

Sjogren syndrome is characterized by fibrosis and focal lymphocytic infiltration into salivary glands.
Patients experience dry mouth, dry eyes, and test positive for anti-Ro/SSA and anti-La/SSB antibodies.

Sodium-Glucose Cotransporter 2 (SGLT-2) Inhibitors

SGLT-2 inhibitors, such as canagliflozin, lower the threshold at which filtered glucose can be fully reabsorbed.
This increases urinary glucose losses and reduces blood glucose levels.

Shigella Species

Shigella species require a low infectious dose to cause gastrointestinal disease.

CD40 Ligand

CD40 ligand is expressed on activated T cells.
It binds to CD40 on antigen-presenting cells, including B cells, leading to their full activation.
Therefore, CD40L plays a critical role in both cell-mediated and humoral immune responses.

Vitamin A Toxicity

Chronic vitamin A toxicity manifests as benign intracranial hypertension (headache, vomiting, papilledema), dry skin, and hepatomegaly.
This occurs due to excessive intake of eggs, liver, or retinoid medications.

Cell Junctions

Gap junctions: composed of connexins, facilitating intercellular communication.
Tight junctions: comprised of claudins and occludin, creating a paracellular barrier.
Adherens junctions and desmosomes: utilize cadherins to anchor cells together.
Hemidesmosomes: employ integrins to anchor cells to the extracellular matrix.

Genital Malformations

Incomplete fusion of the urethral folds in males leads to hypospadias.
Faulty positioning of the genital tubercle results in epispadias.

Niacin Deficiency

Niacin deficiency causes pellagra-like skin eruptions (rough, scaly rash) and cerebellar ataxia.

Diphtheria Treatment

Diphtheria antitoxin is the primary treatment for diphtheria.

Embryonic Origins of Organs

Thymus, liver, and pancreas: endodermal origin.
Spleen, adrenal cortex, and kidneys: mesodermal origin.

Lung Perfusion and Ventilation

Perfusion and ventilation are highest at the base of the lung and lowest at the apex.
The ventilation/perfusion gradient is lowest at the base and highest at the apex.

Wiskott-Aldrich Syndrome

Wiskott-Aldrich syndrome is characterized by a triad of eczema, thrombocytopenia, and combined B and T cell deficiency.
Patients experience repeated infections.

Hypothalamic Nuclei

Ventromedial nucleus: responsible for satiety.
Paraventricular nucleus: involved in the release of oxytocin, corticotropin-releasing hormone (CRH), and thyrotropin-releasing hormone (TRH).

Stellate Cells and Liver Injury

Stellate cells respond to hepatic injury and transform into myofibroblasts, capable of producing collagen.
Collagen stains blue with trichrome stain.

Anion Gap

Normal anion gap: associated with bicarbonate loss due to diarrhea, renal tubular acidosis, or excessive saline infusion.
Elevated anion gap: indicates the accumulation of unmeasured acidic compounds, such as those seen in lactic acidosis, diabetic ketoacidosis, renal failure, or methanol poisoning.

Acute Stress Disorder (ASD) and Post-Traumatic Stress Disorder (PTSD)

ASD exhibits symptoms for up to a month.
After a month, ASD transitions to PTSD.

Alkaptonuria

Alkaptonuria results from an inhibited metabolism of tyrosine to fumarate, leading to the accumulation of homogentisic acid.
Clinical features include black urine and blue-black pigmentation of the face.

Opioid Withdrawal

Opioid withdrawal is marked by mydriasis, abdominal pain, diarrhea, piloerection, lacrimation, and yawning.

Ehlers-Danlos Syndrome

Ehlers-Danlos syndrome is caused by defective collagen synthesis, specifically a deficiency in procollagen peptidase, the enzyme that cleaves terminal propeptides from procollagen in the extracellular space.
Affected individuals exhibit hyperextensible skin and fragile tissues.

Xeroderma Pigmentosum

Xeroderma pigmentosum is an autosomal recessive disorder characterized by defective nucleotide excision repair, often caused by a deficiency in UV-specific endonuclease.

Streptococcus pyogenes Virulence Factor

The major virulence factor of Streptococcus pyogenes is M protein, which extends from the cell wall, preventing phagocytosis and inhibiting complement binding.

Cushing Syndrome

Excess ACTH secretion in ACTH-dependent Cushing syndrome leads to hyperpigmentation.

Gout

Gout occurs more frequently in patients with mutations of phosphoribosyl pyrophosphate synthetase due to increased production and degradation of purines.

Colchicine in Gout

Colchicine is a useful acute management option for gout when NSAIDs are contraindicated.
It inhibits neutrophil chemotaxis and phagocytosis by preventing microtubule formation.

REM Sleep Behavior Disorder

REM sleep behavior disorder is a parasomnia characterized by dream enactment behaviors due to a lack of atonia during REM sleep.
Most patients with idiopathic REM sleep behavior disorder develop disorders of alpha-synuclein neurodegeneration, such as Parkinson's disease.

Hepatitis E

Hepatitis E is an unenveloped virus that particularly affects pregnant women.

Hemoglobin and Myoglobin

Individual subunits of the hemoglobin molecule are structurally similar to myoglobin.
When separated, the monomeric subunits exhibit a hyperbolic oxygen dissociation curve, resembling that of myoglobin.

Rhinitis

In rhinitis, inhaled antigens induce T-helper cells to differentiate into Th2 cells.
Th2 cells promote B cell maturation and isotype class switching to IgE.

Type III Hypersensitivity Reactions

Complement activation occurs in type III hypersensitivity reactions, where immune complexes deposit in the basement membrane of blood vessels or joints.

Lateral Epicondylitis (Tennis Elbow)

Lateral epicondylitis is characterized by overuse of wrist extensor muscles, such as extensor carpi radialis and extensor digitorum, leading to angiofibroblastic tendinosis at their attachment on the lateral epicondyle.

Dissociated Amnesia

Dissociated amnesia involves an isolated inability to recall autobiographical information that is inconsistent with ordinary forgetfulness.
It typically occurs after a traumatic event.

Tetralogy of Fallot

Tetralogy of Fallot presents with four characteristic features: overriding aorta, ventricular septal defect (VSD), narrowed right ventricular outflow tract, and right ventricular hypertrophy.

Leukocyte Adhesion Deficiency

Leukocyte adhesion deficiency results from the absence of CD18 antigens, which are essential for integrin formation.
Failure of leukocyte adhesion and migration leads to recurrent skin and mucosal infections.

Aldolase B Deficiency

Aldolase B deficiency causes hereditary fructose intolerance.
Affected infants present with failure to thrive, jaundice, and hepatomegaly.

Atrial Septal Defect

Atrial septal defect causes wide fixed splitting of S2 due to right-sided volume overload from left-to-right shunting.
Uncorrected defects can lead to irreversible medial hypertrophy of the pulmonary arteries, pulmonary hypertension, and reversal to right-to-left shunting (Eisenmenger syndrome).

Cardiac Conditions and Genetic Factors

Mutations in the TTN gene are associated with familial dilated cardiomyopathy.
Titin, the protein encoded by the TTN gene, plays a role in muscle contraction and structure.

Immune Therapies and Fab Domains

Immunotherapy medications sometimes use the Fab domain for better tissue penetration.
The Fab domain lacks the Fc receptor, preventing complement activation and phagocytosis.

Bone Remodeling and Osteocytes

Osteoblasts differentiate into osteocytes.
Osteocytes detect changes in mechanical bone load.
They communicate via gap junctions to orchestrate bone remodeling.

Epidural Hematomas and Middle Meningeal Artery

Fractures of the frontal, parietal, temporal, and sphenoid bones can cause laceration of the middle meningeal artery, leading to an epidural hematoma.
The middle meningeal artery is a branch of the maxillary artery.

PCOS and Endometrial Cancer Risk

Polycystic ovary syndrome (PCOS) increases the risk of endometrial carcinoma due to increased estrogen production and chronic anovulation.

Vitamin K and Coagulation Factors

Vitamin K acts as a cofactor for gamma-glutamyl carboxylase, an enzyme that activates coagulation factors 2, 7, 9, and 10 through posttranslational gamma carboxylation.

Type IV Hypersensitivity Reactions

Type IV hypersensitivity reactions are mediated by T lymphocytes.
Examples include candida extract skin tests and contact dermatitis.
Allergic contact dermatitis causes Langerhans cells to travel to regional lymph nodes and present antigens to naive T cells, leading to clonal expansion.
Upon re-exposure, sensitized T cells cause tissue damage, manifesting as pruritic erythema, vesicles, and/or bullae 2-3 days after exposure.

Hirschsprung Disease and Neural Crest Cells

Hirschsprung disease results from abnormal migration of neural crest cells (ganglion cell precursors) during embryogenesis.
The rectum is always involved, leading to failure to pass meconium in newborns.

Pancreatic Cancer and KRAS Oncogene

Pancreatic ductal adenocarcinoma often exhibits mutations in the KRAS oncogene.

Burkitt Lymphoma and C-Myc Proto-oncogene

Burkitt lymphoma is associated with the expression of the C-Myc proto-oncogene.
The condition presents with a facial mass.

Chronic Bronchitis and Tobacco Smoking

Chronic bronchitis is characterized by thickened bronchial walls, lymphocytic infiltration, mucous gland enlargement, and patchy squamous metaplasia of the bronchial mucosa.
Tobacco smoking is the primary cause of chronic bronchitis.

Opsonization and Complement

IgG and complement C3b are significant opsonins.
Complement C5a enhances phagocytosis by macrophages by directly binding to receptors on phagocytes.

Neurofibromatosis Type I and Schwann Cells

Cutaneous neurofibromas, present in Neurofibromatosis type I, are composed of Schwann cells.
Schwann cells originate from neural crest cells during embryonic development.

Infective Endocarditis in IV Drug Users

Infective endocarditis in intravenous drug users commonly affects the tricuspid valve.

Myotonic Dystrophy and Trinucleotide Repeat Expansion

Myotonic dystrophy is an autosomal dominant condition caused by trinucleotide repeat expansion.
Successive generations experience an increased number of repeats.
Affected individuals often exhibit cognitive issues and muscle weakness.

Reciprocal Induction in Development

Reciprocal induction is a type of signaling between two tissues, where both must be present to induce normal development.
This occurs in the kidney and the eye.

Acid-Fast Stain and Mycolic Acid

The acid-fast stain identifies organisms containing mycolic acid in their cell walls.

Cortisol and Adrenal Medulla

Cortisol increases the conversion of norepinephrine to epinephrine in the adrenal medulla by enhancing the expression of phenylethanolamine-N-methyltransferase.

Atopic Dermatitis and Th2 Cytokines

Atopic dermatitis is associated with Th2 cytokines (IL-4 and IL-13) that stimulate IgE production.

Communicating Hydroceles and Indirect Inguinal Hernias

Communicating hydroceles and indirect inguinal hernias result from an incomplete obliteration of the processus vaginalis.

Blood-Testis Barrier and Sertoli Cells

The blood-testis barrier is formed by tight junctions between Sertoli cells in the seminiferous tubules, preventing immune exposure to developing spermatids.

Cranial Nerves and Foramina

Foramen rotundum houses CN V2 (maxillary).
Foramen ovale houses CN V3 (mandibular).
Foramen spinosum houses the middle meningeal artery and vein.

Folate Deficiency and Megaloblastic Anemia

Folate deficiency inhibits nucleic acid synthesis, particularly thymidine formation.
This leads to defective DNA synthesis and increased apoptosis affecting hemopoietic cells (resulting in megaloblastic anemia).

ADH and Concentrated Urine Production

Antidiuretic hormone (ADH) acts on the medullary segment of the collecting duct to increase urea and water reabsorption, allowing for the production of maximally concentrated urine.

Henoch-Schonlein Purpura and IgA Deposition

Henoch-Schonlein purpura is an IgA-mediated, leukocytoclastic vasculitis that manifests as palpable purpura, arthralgia/arthritis, abdominal pain, and hematuria.
Renal involvement is due to mesangial deposition of IgA immune complexes.

Neural Tube Defects and Alpha-Fetoprotein

Open neural tube defects (NTDs) allow alpha-fetoprotein and acetylcholinesterase to leak into amniotic fluid, leading to elevated levels detected during amniocentesis.

Duodenal Compression and Bilious Vomiting

The transverse segment of the duodenum traverses through a mesenteric fat pad that provides structural support for the superior mesenteric artery (SMA).
Compression can cause recurrent bilious vomiting.

Viral Receptor Binding

CD4 binds to HIV gp120.
CD21 binds to Epstein-Barr virus gp350.
Erythrocyte P antigen binds to Parvovirus B19.

Leukocyte Adhesion and Transmigration

ICAMs mediate neutrophil tight adhesion.
PCAMs mediate neutrophil transmigration.

Herpes Simplex Virus (HSV) Transport

HSV infection initially utilizes dynein for retrograde transport.
Later, kinesin is used for anterograde transport.

Ecological Studies and Units of Analysis

Ecological studies analyze populations, not individuals.
They cannot be used to draw conclusions about individuals.

Protein Targeting and Posttranslational Modifications

Posttranslational modifications of proteins are crucial for targeting them to the correct cellular locations.

Stimulant Medications for ADHD

Stimulant medications are used in Attention-Deficit/Hyperactivity Disorder (ADHD).
They work by increasing norepinephrine and dopamine availability in the prefrontal cortex.

Vestibular Schwannomas and Cerebellopontine Angle

Vestibular schwannomas can cause hearing loss, ipsilateral facial paresthesia, and ipsilateral facial paresis.
They are located at the cerebellopontine angle.

Pheochromocytoma and Adrenal Medulla

Pheochromocytoma is a malignancy arising from the chromaffin cells of the adrenal medulla.
Adrenal medulla originates from neural crest cells.

Superficial Thermal Burn Responses

The earliest morphological change after a superficial thermal burn is erythema due to the release of preformed mediators like histamine from mast cells.

Blister Formation in Deeper Burns

Deeper burn wounds form blisters due to fluid extravasation through gaps between damaged venule endothelial cells.

Protein A and Staphylococcus aureus

Protein A, a virulence factor in Staphylococcus aureus, binds to the Fc portion of IgG, inhibiting complement activation, opsonization, and phagocytosis.

Sjogren Syndrome and Autoantibodies

Sjogren syndrome is characterized by fibrosis and focal lymphocytic infiltration into salivary glands.
Patients present with dry mouth, dry eyes, and test positive for anti-Ro/SSA and anti-La/SSB antibodies.

SGLT-2 Inhibitors and Blood Glucose Control

SGLT-2 inhibitors like canagliflozin lower the threshold for glucose reabsorption in the kidneys.
This increases urinary glucose losses and reduces blood glucose levels.

Shigella Species and Low Infectious Dose

Shigella species require a low infectious dose to cause gastrointestinal disease.

CD40 Ligand and Immune Response

CD40 ligand is expressed on activated T cells.
It binds to CD40 on antigen-presenting cells, including B cells, promoting their full activation.
CD40L plays a critical role in both cell-mediated and humoral immune responses.

Chronic Vitamin A Toxicity

Chronic vitamin A toxicity can lead to benign intracranial hypertension (headache, vomiting, papilledema), dry skin, and hepatomegaly.
Excessive intake of egg, liver, or retinoid medications can cause this.

Cellular Junctions and Their Functions

Gap junctions, composed of connexins, facilitate intercellular communication.
Tight junctions, formed by claudins and occludin, create a paracellular barrier.
Adherens junctions and desmosomes, composed of cadherins, provide cellular anchoring.
Hemidesmosomes, composed of integrins, also provide cellular anchoring.

Hypospadias and Epispadias

Hypospadias in males arises from incomplete fusion of the urethral folds.
Epispadias results from faulty positioning of the genital tubercle.

Niacin Deficiency and Pellagra

Niacin deficiency can lead to pellagra, characterized by skin eruptions (rough, scaly rash) and cerebellar ataxia.

Diphtheria Treatment

The primary treatment for diphtheria is diphtheria antitoxin.

Tissue Origins

Thymus, liver, and pancreas all originate from endoderm.
Spleen, adrenal cortex, and kidneys originate from mesoderm.

Ventilation and Perfusion in the Lungs

Perfusion and ventilation are highest at the base of the lung and lowest at the apex.
The ventilation/perfusion gradient is lowest at the base and highest at the apex.

Wiskott-Aldrich Syndrome

Wiskott-Aldrich syndrome is characterized by the triad of eczema, thrombocytopenia, and combined B and T cell deficiency.
Patients suffer from recurrent infections.

Hypothalamic Nuclei and Functions

The ventromedial nuclei control satiety.
The paraventricular nuclei are responsible for the release of oxytocin, corticotropin-releasing hormone (CRH), and thyrotropin-releasing hormone (TRH).

Stellate Cells and Liver Injury

Stellate cells respond to hepatic injury by transforming into myofibroblasts that produce collagen.
Collagen stains blue with a trichrome stain.

Anion Gap Interpretation

Normal anion gap is associated with loss of bicarbonate, often seen in diarrhea, renal tubular acidosis, or excessive saline infusion.
Elevated anion gap suggests accumulation of unmeasured acidic compounds, such as in lactic acidosis, diabetic ketoacidosis, renal failure, or methanol ingestion.

Acute Stress Disorder vs. PTSD

Acute stress disorder exhibits symptoms for up to a month.
After a month, it transitions into post-traumatic stress disorder (PTSD).

Alkaptonuria

Alkaptonuria results from inhibition of tyrosine metabolism to fumarate, leading to accumulation of homogentisic acid.
Clinical features include black urine and blue-black pigmentation of the face.

Opioid Withdrawal Syndrome

Opioid withdrawal is characterized by mydriasis, abdominal pain, diarrhea, piloerection, lacrimation, and yawning.

Ehlers-Danlos Syndrome

Ehlers-Danlos syndrome involves defective collagen synthesis due to a deficiency in procollagen peptidase, the enzyme responsible for cleaving terminal propeptides from procollagen in the extracellular space.
Affected individuals have hyperextensible skin and fragile tissues.

Xeroderma Pigmentosum

Xeroderma pigmentosum is an autosomal recessive disorder characterized by defective nucleotide excision repair, often caused by a deficiency in UV-specific endonuclease.

Streptococcus pyogenes Virulence Factor

The M protein, a major virulence factor of Streptococcus pyogenes, extends from the cell wall, preventing phagocytosis and inhibiting complement binding.

ACTH Dependent Cushing Syndrome

Excess ACTH secretion, as seen in ACTH-dependent Cushing syndrome, causes hyperpigmentation.

Gout and Phosphoribosyl Pyrophosphate Synthetase

Gout occurs more frequently in patients with mutations in phosphoribosyl pyrophosphate synthetase, leading to increased purine production and degradation.

Colchicine in Gout Management

When NSAIDs are contraindicated in gout, colchicine is useful for acute management by inhibiting neutrophil chemotaxis and phagocytosis.
It achieves this by preventing microtubule formation.

REM Sleep Behavior Disorder

REM sleep behavior disorder is a parasomnia characterized by dream enactment behaviors due to a loss of atonia during REM sleep.
Most patients with idiopathic RBD develop disorders of alpha-synuclein neurodegeneration, such as Parkinson's disease.

Hepatitis E

Hepatitis E is an unenveloped virus that disproportionately impacts pregnant women.

Hemoglobin and Myoglobin

Individual subunits of a hemoglobin molecule are structurally analogous to myoglobin.
When separated, the monomeric subunits exhibit a hyperbolic oxygen dissociation curve, similar to that of myoglobin.

Rhinitis and IgE Production

In rhinitis, inhaled antigens induce T-helper cells to differentiate into Th2 cells.
Th2 cells then promote B cell maturation and isotype class switching to IgE.

Type III Hypersensitivity Reactions

Complement activation plays a role in Type III hypersensitivity reactions, where immune complexes deposit in the basement membrane of blood vessels or joints.

Lateral Epicondylitis

Lateral epicondylitis (tennis elbow) is caused by overuse of wrist extensor muscles like extensor carpi radialis and extensor digitorum.
This leads to angiofibroblastic tendinosis at their attachment on the lateral epicondyle.

Dissociated Amnesia

Dissociated amnesia involves an isolated inability to recall autobiographical information, inconsistent with a ordinary forgetfulness.
It often occurs after a traumatic event.

Tetrology of Fallot

Tetrology of Fallot is characterized by four key features:
- Overriding aorta
- Ventricular septal defect (VSD)
- Narrowed right ventricular outflow tract
- Right ventricular hypertrophy

Leukocyte Adhesion Deficiency

Leukocyte adhesion deficiency is caused by the absence of CD18 antigens, which are essential for forming integrins.
This leads to failure of leukocyte adhesion and migration, resulting in recurrent skin and mucosal infections.

Aldolase B Deficiency and Hereditary Fructose Intolerance

Aldolase B deficiency causes hereditary fructose intolerance.
Affected infants present with failure to thrive, jaundice, and hepatomegaly.

Atrial Septal Defect

Atrial septal defects result in wide fixed splitting of S2, due to right-sided volume overload from left-to-right shunting.
Uncorrected defects can lead to irreversible medial hypertrophy of the pulmonary arteries, causing pulmonary hypertension and potentially reversal to right-to-left shunting (Eisenmenger syndrome).

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Test your knowledge on various medical topics including familial dilated cardiomyopathy, immunotherapy, bone remodeling, epidural hematoma, and polycystic ovarian syndrome (PCOS). This quiz covers key concepts, mechanisms, and implications related to these conditions. Dive in to evaluate your understanding of these crucial medical subjects.