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Endocrine system


Pharyngeal arches, pouches, and clefts

Endocrine system anatomy and physiology

Anatomy of the thyroid and parathyroid glands

Anatomy of the abdominal viscera: Pancreas and spleen

Pituitary gland histology

Thyroid and parathyroid gland histology

Pancreas histology

Adrenal gland histology

Synthesis of adrenocortical hormones

Adrenocorticotropic hormone

Growth hormone and somatostatin

Hunger and satiety

Antidiuretic hormone

Thyroid hormones







Estrogen and progesterone

Oxytocin and prolactin

Parathyroid hormone


Vitamin D

Phosphate, calcium and magnesium homeostasis

Congenital adrenal hyperplasia

Adrenal insufficiency: Pathology review

Primary adrenal insufficiency

Waterhouse-Friderichsen syndrome


Cushing syndrome and Cushing disease: Pathology review

Cushing syndrome

Conn syndrome


Adrenal masses: Pathology review

Adrenal masses and tumors: Clinical (To be retired)

Adrenal cortical carcinoma

Thyroglossal duct cyst


Hyperthyroidism: Pathology review

Graves disease

Thyroid eye disease (NORD)

Toxic multinodular goiter

Euthyroid sick syndrome


Hypothyroidism: Pathology review

Hashimoto thyroiditis

Hypothyroidism and thyroiditis: Clinical (To be retired)

Subacute granulomatous thyroiditis

Riedel thyroiditis

Thyroid storm

Thyroid nodules and thyroid cancer: Pathology review

Thyroid cancer

Thyroid nodules and thyroid cancer: Clinical (To be retired)

Parathyroid disorders and calcium imbalance: Pathology review

Parathyroid conditions and calcium imbalance: Clinical (To be retired)





Diabetes mellitus

Diabetes mellitus: Pathology review

Diabetes mellitus: Clinical (To be retired)

Diabetic nephropathy

Diabetic retinopathy

Pancreatic neuroendocrine neoplasms

Diabetes insipidus and SIADH: Pathology review

Diabetes insipidus

Syndrome of inappropriate antidiuretic hormone secretion (SIADH)

Hypopituitarism: Pathology review



Pituitary adenoma

Pituitary apoplexy

Pituitary tumors: Pathology review

Sheehan syndrome






Constitutional growth delay

Puberty and Tanner staging

Precocious puberty

Delayed puberty

Kallmann syndrome

Disorders of sex chromosomes: Pathology review

5-alpha-reductase deficiency

Menstrual cycle

Polycystic ovary syndrome

Premature ovarian failure


Androgen insensitivity syndrome

Autoimmune polyglandular syndrome type 1 (NORD)

Multiple endocrine neoplasia: Pathology review

Multiple endocrine neoplasia

Carcinoid syndrome


Opsoclonus myoclonus syndrome (NORD)

Hyperthyroidism medications

Hypothyroidism medications

Hypoglycemics: Insulin secretagogues

Miscellaneous hypoglycemics

Mineralocorticoids and mineralocorticoid antagonists

Adrenal hormone synthesis inhibitors

Anatomy of the gastrointestinal organs of the pelvis and perineum

Anatomy of the oral cavity (dentistry)

Anatomy of the pharynx and esophagus

Anatomy of the anterolateral abdominal wall

Anatomy of the abdominal viscera: Blood supply of the foregut, midgut and hindgut

Anatomy of the abdominal viscera: Esophagus and stomach

Anatomy of the abdominal viscera: Small intestine

Anatomy of the abdominal viscera: Large intestine

Anatomy of the abdominal viscera: Pancreas and spleen

Anatomy clinical correlates: Anterior and posterior abdominal wall

Abdominal quadrants, regions and planes

Development of the digestive system and body cavities

Development of the gastrointestinal system

Development of the teeth

Development of the tongue

Gallbladder histology

Esophagus histology

Stomach histology

Small intestine histology

Colon histology

Liver histology

Pancreas histology

Gastrointestinal system anatomy and physiology

Anatomy and physiology of the teeth

Liver anatomy and physiology

Escherichia coli

Salmonella (non-typhoidal)

Yersinia enterocolitica

Clostridium difficile (Pseudomembranous colitis)


Salmonella typhi (typhoid fever)

Clostridium perfringens

Vibrio cholerae (Cholera)



Bacillus cereus (Food poisoning)

Campylobacter jejuni

Bacteroides fragilis


Enteric nervous system

Esophageal motility

Gastric motility

Gastrointestinal hormones

Chewing and swallowing

Carbohydrates and sugars

Fats and lipids


Vitamins and minerals

Intestinal fluid balance

Pancreatic secretion

Bile secretion and enterohepatic circulation

Prebiotics and probiotics

Cleft lip and palate



Oral candidiasis

Aphthous ulcers

Ludwig angina

Warthin tumor

Oral cancer

Dental caries disease

Dental abscess

Gingivitis and periodontitis

Temporomandibular joint dysfunction

Nasal, oral and pharyngeal diseases: Pathology review

Esophageal disorders: Pathology review

Esophageal web

Esophagitis: Clinical (To be retired)

Barrett esophagus


Zenker diverticulum

Diffuse esophageal spasm

Esophageal cancer

Esophageal disorders: Clinical (To be retired)

Boerhaave syndrome

Plummer-Vinson syndrome

Tracheoesophageal fistula

Mallory-Weiss syndrome

GERD, peptic ulcers, gastritis, and stomach cancer: Pathology review

Gastroesophageal reflux disease (GERD)

Peptic ulcer

Helicobacter pylori


Peptic ulcers and stomach cancer: Clinical (To be retired)

Pyloric stenosis

Zollinger-Ellison syndrome

Gastric dumping syndrome


Gastric cancer


Small bowel bacterial overgrowth syndrome

Irritable bowel syndrome

Celiac disease

Small bowel ischemia and infarction

Tropical sprue

Short bowel syndrome (NORD)

Malabsorption syndromes: Pathology review

Malabsorption: Clinical (To be retired)

Zinc deficiency and protein-energy malnutrition: Pathology review

Whipple's disease

Appendicitis: Pathology review


Appendicitis: Clinical (To be retired)

Lactose intolerance

Protein losing enteropathy

Microscopic colitis

Inflammatory bowel disease: Pathology review

Crohn disease

Ulcerative colitis

Inflammatory bowel disease: Clinical (To be retired)

Bowel obstruction

Bowel obstruction: Clinical (To be retired)


Familial adenomatous polyposis

Juvenile polyposis syndrome

Gardner syndrome

Colorectal polyps and cancer: Pathology review

Colorectal polyps

Colorectal cancer

Colorectal cancer: Clinical (To be retired)

Peutz-Jeghers syndrome

Diverticulosis and diverticulitis

Diverticular disease: Pathology review

Diverticular disease: Clinical (To be retired)

Intestinal adhesions

Ischemic colitis



Cyclic vomiting syndrome

Abdominal hernias

Femoral hernia

Inguinal hernia

Hernias: Clinical (To be retired)

Congenital gastrointestinal disorders: Pathology review

Congenital diaphragmatic hernia

Imperforate anus



Meckel diverticulum

Intestinal atresia

Hirschsprung disease

Intestinal malrotation

Necrotizing enterocolitis


Anal conditions: Clinical (To be retired)

Anal fissure

Anal fistula


Rectal prolapse

Carcinoid syndrome

Crigler-Najjar syndrome

Biliary atresia

Gilbert's syndrome

Dubin-Johnson syndrome

Rotor syndrome

Jaundice: Pathology review



Cirrhosis: Pathology review

Cirrhosis: Clinical (To be retired)

Portal hypertension

Hepatic encephalopathy


Wilson disease

Budd-Chiari syndrome

Non-alcoholic fatty liver disease

Cholestatic liver disease

Hepatocellular adenoma

Alcohol-induced liver disease

Alpha 1-antitrypsin deficiency

Primary biliary cirrhosis


Hepatitis A and Hepatitis E virus

Hepatitis B and Hepatitis D virus

Viral hepatitis: Pathology review

Viral hepatitis: Clinical (To be retired)

Autoimmune hepatitis

Primary sclerosing cholangitis

Neonatal hepatitis

Reye syndrome

Benign liver tumors

Hepatocellular carcinoma

Gallbladder disorders: Pathology review


Gallstone ileus

Biliary colic

Acute cholecystitis

Ascending cholangitis

Chronic cholecystitis

Gallbladder cancer

Gallbladder disorders: Clinical (To be retired)


Pancreatic pseudocyst

Acute pancreatitis

Chronic pancreatitis

Pancreatitis: Clinical (To be retired)

Pancreatic cancer

Pancreatic neuroendocrine neoplasms

Pancreatitis: Pathology review

Abdominal trauma: Clinical (To be retired)

Gastrointestinal bleeding: Pathology review

Gastrointestinal bleeding: Clinical (To be retired)

Pediatric gastrointestinal bleeding: Clinical (To be retired)

Abdominal pain: Clinical (To be retired)

Disorders of carbohydrate metabolism: Pathology review

Glycogen storage disorders: Pathology review

Glycogen storage disease type I

Glycogen storage disease type II (NORD)

Environmental and chemical toxicities: Pathology review

Medication overdoses and toxicities: Pathology review

Laxatives and cathartics


Acid reducing medications




USMLE® Step 1 questions

0 / 3 complete

High Yield Notes

17 pages


USMLE® Step 1 style questions USMLE

of complete

A 16-year-old boy is brought to urgent care for evaluation of crampy abdominal pain and diarrhea. The patient has noticed bright red blood and mucus mixed with stool. Temperature is 38.4 °C (101.3 °F), blood pressure is 103/76 mmHg, pulse is 108/min and respirations are 16/min. Physical examination shows dry mucous membranes. There is mild diffuse abdominal tenderness to palpation. Stool cultures show an immotile Gram-negative organism that produces a toxin capable of inhibiting the 60S ribosomal subunit. Which of the following statements is true regarding the pathogen responsible for this patient’s symptoms?  

Memory Anchors and Partner Content


Content Reviewers

Viviana Popa, MD


Kaylee Neff

Tanner Marshall, MS

Kaia Chessen, MScBMC

Shigella is a Gram-negative bacterium that belongs to the Enterobacteriaceae family.

There are 4 species of Shigella:

S. dysenteriae, S. flexneri; S. boydii; and S. sonnei, and each has its own serotypes.

In humans these species can all cause Shigellosis, which is a contagious infection of the intestines, particularly the colon.

And shigellosis can progress to dysentery, which is when the infection causes inflammation of the colon, resulting in severe abdominal pain and diarrhea.

Now, Shigella is a gram-negative, rod shaped bacterium, meaning it looks like a little red or pink stick on a gram stain.

And it’s a facultative anaerobe, so it can survive with or without oxygen in the environment.

It has no flagellum, making it nonmotile; and it doesn’t form spores.

It’s also a non-lactose fermenter, so it doesn’t ferment lactose; and it’s urease and oxidase-negative, meaning it doesn’t produce these enzymes.

Finally, it doesn’t produce hydrogen sulfide gas either, and this can be used to selectively identify Shigella on special culture mediums like MacConkey agar.

On this medium, Shigella mostly forms white, non-lactose fermenting, non-hydrogen sulfide-producing colonies

Now, once Shigella is ingested, it multiplies in the small intestine, and then passes into the colon.

There, it targets the epithelial layer of the mucosal lining where it infects colonic enterocytes and microfold cells, or M-cells.

And these M-cells phagocytose, which means they eat the bacteria from the intestinal lumen, and then spit it out into the underlying mucosa-associated lymphoid tissues, or MALTs.

MALTs are a type of mucosal immune tissue that extends into the submucosa, and contains plenty of immune cells like macrophages.

The macrophages gobble up Shigella to neutralize the pathogen, but the bacterium induces apoptosis, or programmed cell death, in the macrophage.


Shigella is a genus of bacteria known to cause a contagious form of gastroenteritis known as shigellosis. Shigellosis is characterized by an inflammation of the gastrointestinal tract, which causes destruction and inflammation of the epithelium, leading to dysentery with symptoms like severe abdominal and rectal cramping and pain, a fever, and watery diarrhea with mucous with or without blood or pus. Shigella is transmitted through the fecal-to-oral route, mainly through fingers, food, and flies. It's diagnosed with a fecal sample and treatment centers around fluid and electrolyte replenishment and antibiotics.


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