Histology of blood and hematopoiesisDownloads

A 66-year-old man comes to the physician for a 3-month history of fatigue. He has hypertension and hyperlipidemia. He had a transient ischemic attack 3 years ago. He drinks 3 beers a day, and sometimes a couple more on social occasions. He currently takes aspirin, simvastatin, hydrochlorothiazide, and metoprolol. His temperature is 37.1°C (98.8°F), pulse is 78, respirations are 19/min, and oxygen saturation on room air is 97%. He is in no distress but shows marked pallor and has multiple pinpoint, red, nonblanching spots on his extremities. On palpation, his spleen is significantly enlarged. Laboratory studies show a hemoglobin of 8.0 g/dL, a leukocyte count of 80,000/mm3, and a platelet count of 34,000/mm3. A blood smear shows immature cells with large, prominent nucleoli and pink, elongated, needle-shaped cytoplasmic inclusions. Which of the following is the most likely diagnosis?

During the third week of development, the blastocyst undergoes a variety of differentiation processes responsible for the formation of the gastrula and, eventually, the embryo. This differentiation creates cell lineages that eventually become a variety of body systems. What cell lineage, present at this date, is responsible for the formation of the liver?