Week 8 - Haematopoiesis and germline

• 2 major components of blood?

  Plasma and cells (Erythrocytes, platelets and leukocytes)
• 3 major roles of blood? What related symptom might appear if experiencing significant blood loss?

  Transporting nutrients, regulate body temperature, pH, electrolytes, glucose, protect against infection.

  prevent blood loss following injury
• 2 substances transported by plasma

  Plasma proteins like albumin, antibodies, fibrinogen.

  inorganic salts,

  amino acids, vitamins, hormones, lipoproteins
• Are lymphocytes produced in the yolk sac?

  NO
• 3 differences between embryonic and adult erythrocytes?

  Embryo: large and nucleated, express embryo globin genes and derived from yolk sac.
• what happens in the final yolk sac?

  A section of yolk sac surrounded by endoderm
• What happens in primitive haemotopoiesis?

  Week 3 day 18 of development: Mesenchymal cells in yolk sac form Blood island with haemangioblasts. Angioblasts form which form blood vessel
• What triggers the formation of hemangioblast from lateral plate mesoderm?

  BMP.
• What will haemangioblast form?

  Angioblast, and pluripotent haematopoietic stem cells then lymphoid stem cells or blood stem cells.
• Vitelline vein and artery connect to which vein and artery?

  Umbilical
• are platelets cells?

  No they are cell fragments
• Haemophilia

  Excessive bleeding due to genetic mutations causing low platelets
• Nucleus consists of 2-5 lobes linked by chromatin. What cells?

  Neutrophils
• Neutrophilia vs neutropenia?

  Neutrophilia: high neutrophil count. Neutropenia: low neutrophil count.
• Bilobed nucleus. often associated with allergic disorders. What cell?

  Eosinophils
• Smallest of granular leukocytes, bill bee nucleus and violet or black granules

  Basophils
• Largest of all cells. Has fine granules but considered agranular. phagocyte that engulf bacteria

  Monocyte
• What is the transformation of locations of definitive haemopoiesis?

  First in aorta-gonad-mesonephros region then liver, placenta, spleen then bone.
• Differences between primitive and definitive phases of haematopoiesis?

  Timing, sites of blood cell production, globin genes active in RBC, morphology of cells produced
• When does definitive haemopoiesis occur


  28 days in humans? Fetal stage
• Where do Vitelline vessels link to? Where do placental vessels link to?

  Vitelline vessels link to the yolk sac. Placental vessels link to the placenta.
• What time ind development do primitive and definitive haematopoiesis occur?

  First 5-6 weeks: primitive

  by 5-6 weeks definitive occurs (haemopoiesis begins in fetal liver)
• What are colony stimulating factors?

  Made by Stromal cells of bone marrow. They stimulate growth and differentiation of progenitor cells in colonies with different blood cell types in vitro
• Function of neutrophils

  Surround bacterium by pseudopodia

  azurophilic granules discharge enzymes into acidic environment, killing bacteria by phagocytosis
• Functions of basophils?

  release of granules lead to vascular dilation so immune cells specifically granulocytes like neutrophils and eosinophils can come, bronchorestriction
• Functions of monocytes

  After crossing capillary walls and enter connective tissue differentiate into macrophages, Phagocytes destroy bacteria also present antigen to T cells
• function of BLIMP1 gene in specification?

  suppress genes that drive cells into somatic pathway, keeping those cells pluripotent.
• Function of Stella in commitment

  Commitment to germline
• Development of germline steps!

  Specification: 6 primordial germ cells, BLIMP1 expressed to keep pluripotency

  commitment: Stella make cells commit to germline

  migration and proliferation: active and passive to gonads

  colonisation and undergo sex determination:

  if enter ovary becomes oogonia, start meiosis arrest at prophase 1 until puberty

  if enter testis becomes gonocytes, mitosis arrest mitosis,. At birth becomes intermediate soermatogonia, enter meiosis in puberty
• Differences in meiosis between males and females

  Females asymmetrical and timing of maturation different and location and temperature
• What stage of meiosis is reductive stage?

  I becomes the chromosomes separate
• Major stages of spermatogenesis?

  In testis, have seminiferous tubules: spermatogonial stem cell then primary spermatocytes, secondary soermatocytes, Spermatids (start to compact) mature sperm or spermatozoa release into lumen of tube. Sertoli cells support, produce anti-Mullerian hormones regress mullerian ducts, form blood testis barrier making sure sperms are protected from immune system. Testosterone produced by Leydig cells impact internal and external reproductive structures.
• Theca cells function

  Theca cells produce eostrogen
• What stages are in definitive stage

  Fetal and post natal stage
• Where in the cell can you detect SRY?

  Nucleus because master transcription factor
• Homologous structures?


  Clitoris and penis, labia majora and scrotum
• List 2 molecular causes of alterations in sex determination

  Mutations so SRY does not function, working SRY but signalling not functioning like androgen receptor may be mutated so none of the cells are responding correctly to testosterone.
• Where does primitive haematopoiesis occur?


  Yolk sac, the splanchnic mesoderm derived from the yolk sac