Embryology Lecture 1 Introduction Flashcards
What is the clinical importance of studying embryology?
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Developing new techniques for prenatal diagnosis and treatments
Identifying therapies for infertility
Understanding mechanisms to prevent birth defects
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How does organ formation occur?
Organs are formed by interactions between cells and tissues
True or False: Cross talk between the two cell/tissue types is essential for differentiation to continue
True
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What are two important examples where epithelial-mesenchymal interactions are important for the development of organs
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What are the 4 types of Growth and Differentiation Factors (GDFs)
Fibroblast Growth factor (FGFs)
WNT
Hedgehog
Transforming Growth factor beta (TGF-β)
_____ is important for angiogenesis and mesoderm differentiation
Fibroblast Growth Factor (FGFs)
FGF8 is important for limb development
What is WNT (wingless and integrated or int-1) involved in?
¤Urogenital differentiation
¤Midbrain development
¤Limb patterning
¨Sonic hedgehog (SHH) is important for:
¤Neural tube induction and patterning
¤Gut regionalization
¤Somite differentiation
¤Limb patterning
Action is mostly inhibiting an inhibitor
Transforming Growth Factor- beta (TGF-β) is important for?
¤Extracellular matrix formation
¤Epithelial branching that occurs in the lung, kidney, and salivary gland development
¤Bone Morphogenetic Proteins:
Regulate cell division, cell migration, and apoptosis
Induce bone formation
What two types of neurotransmitters important for embryonic cell signaling?
Serotonin:
¨Establishing laterality
¨Heart development
¨Gastrulation
¨Cell migration
¨Cell Proliferation
Noradrenalin:
¨Apoptosis in interdigital spaces
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Summary of Cell Signalling Substances
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What are the male and female gametes called?
Spermatozoon (male gamete; plural: spermatozoa)
Oocyte (female gamete)
True or False: Both gametes develop from primordial germ cells
True
Primordial Germ Cells
Formed in the ______ during the 2nd week of development
Move through _______ during _______
Migrate to the wall of the ______
Position themselves close to the attachment of future umbilical cord (near the caudal end of the developing embryo)
¤By the end of 5th week of development they arrive in the _______
Epiblast
primitive streak, gastrulation
yolk sac
developing gonads
Explain male spermatogenesis?
At puberty, primordial germ cells differentiate into type A spermatogonia (46,2N)
Type A spermatogonia divide by mitosis to form either more type A spermatogonia (to maintain the supply) or type B spermatogonia
¨Type B spermatogonia produce primary spermatocytes
Primary spermatocytes undergo meiotic division to form spermatids:
Spermatocytogenesis
Spermatids transform into spermatozoa:
Spermiogenesis (no division only change in shape)
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Release of acrosomal enzymes as sperm touches zona pellucida is called ______
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ACROSOME REACTION
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Less than ______ sperm/ml semen causes male infertility
10 million
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What percent of sperm are viable and what percent are motile?
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55%
20% are morphologically abnormal
25% are non-motile
Normal Motility: At least 40% should be actively motile
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Where does maturation of sperm occur? What is capacitation?
¤Occurs in epididymis
¤Glycoprotein coat and seminal plasma proteins are removed from the plasma membrane that covers the acrosome of the sperm
¤Only capacitated sperms can pass through corona radiata cells and undergo acrosome reaction
Most of ______ occurs during embryonic development
Primordial germ cells migrate into the ovaries at week 4 of development and differentiate into ______ (46,2N)
Oogonia enter ______ and undergo DNA replication to form ______
oogenesis
oogonia
meiosis I, primary oocytes (46,2N)
True or False: All primary oocytes are formed by the fifth month of fetal life and remain dormant in the prophase of meiosis I until puberty
True
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Explain cell division during follicle maturation
Graafian follicle, Ovulation & Corpus Luteum Overview
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Due to ______ from the anterior pituitary, occurs 14 days before the next menstruation
LH surge
ovulatory day = duration of menstrual cycle -14 ; e.g. if menstrual cycle is of 30 days then ovulation will occur on 30 -14 = 16th day
Explain the corpus luteum
¨Walls of follicle after ovulation
¨Become glandular under influence of LH, secrete progesterone for a brief period, degenerate in 10-12 days if pregnancy doesn’t occur - corpus luteum of menstruation
¨If pregnancy occurs, degeneration of corpus luteum is prevented by human chorionic gonadotropin (hCG) - corpus luteum of pregnancy
¤Remains functionally active throughout the first 20 weeks of pregnancy
human chorionic gonadotropin (hCG) is secreted by syncytiotrophoblast of placenta
After 20weeks of pregnancy, the placenta assumes the production of the estrogen and progesterone that is necessary for the maintenance of pregnancy
Summary of oocyte at ovulation
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_____ is
¤Glycoprotein membrane surrounding the plasma membrane of an oocyte
¤Secreted by oocyte and granulosa cells
¤Non sticky
______ is
¤Granulosa cells surrounding oocyte membrane after ovulation
Zona pellucida
Corona radiata
What are the functions of the zona pellucida?
¨Prevents:
¤Polyspermy
¤Premature implantation (zygote needs to develop into blastocyst for implantation)
¤Disintegration of cleaving embryo
¤Immunological reaction (because it has no major histocompatibility (HLA) antigens
Allows:
¤Nutrients to reach cleaving embryo
¤Blastocyst development
Comparison of Spermatogenesis and Oogenesis
Comparison of Gametes
What are the effects of offspring of older women and men?
Older Women:
¨Prolonged dormancy of primary oocytes may cause chromosomal abnormalities
¨Trisomy 21 increases with advanced age of the mother
Older Men:
¨With advanced paternal age increased incidence of:
Achondrplasia:
Retarded growth of long bones
Marfan Syndrome:
Disorder of connective tissue
