Medical Post Graduation | Anatomy | Embryology

Practice Medical Post Graduation | Anatomy | Embryology on Bissoy — browse topics below and open any question.

Questions

Barr body is

ক

Found in interphase of the cell cycle

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Discovered by Murray Llewellyn Barr

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Located just below the nuclear membrane

ঘ

Absent in normal male

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Diagnostic of a genetic female

To prevent polyspermy, fertilization initiates the cortical reaction which involves

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Alteration of the binding affinity of sperm receptors on the surface

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Inhibition of the acrosomal reaction in subsequent sperm

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Release of the contents of the cortical granules by fusion with the plasma membrane

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Development of gap between the zona pellucida and the plasma membrane

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Rapid membrane repolarization

The trophoblast

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Is formed from their outer layer of cells of the blastocyst

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Is the means whereby the embryo embeds itself in the wall of the uterus

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Forms the wall of the chorionic villi

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Consists of an outer cytotrophoblast and an inner syncytiotrophoblast

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Can digest other layers in addition to the endometrium of the uterus

The human oocyte

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Is about 100-150 ïm in diameter when the ovarian follicle ruptures

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Undergoes the second meiotic division after fertilization

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Is surrounded by a layer of cells called the stratum granulosum

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Undergoes the first meiotic division after ovulation

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Undergoes the second meiotic division after the disappearance of the zona pellucida

The following times are correct

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The dividing zygote (fertilized ovuis in the uterine tube for about 3 days

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The uterine cavity is obliterated by the fusion of the decidua capsularis and decidua parietalis at about the 15th week of pregnancy

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The blastocyst embeds in the uterine wall about 15 days after fertilization

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An ovum can be fertilzed for 4 days after ovulation

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If pregnancy occurs the corpus luteum degenerates within 10 days of its formation

Human spermatozoa

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Contain 23 chromosomes

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Require FSH and testosterone for development

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Are motile in seminiferous tubule

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Need body temperature for storing

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Are mostly bifid

The ovary developed from

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Coelomic epithelium

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Definitive yolk sac

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Mesenchyme beneath the genital ridge

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Amniotic membrane

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Chorionic membrane

At the time of ovulation

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The first meiotic division has just occurred

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Expulsion of the first polar body has just occurred

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The Secondary oocyte is arrested in the second maturation division

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The zona pellucida has broken down

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Fertilization is not possible

Ovulation

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Releases the oocytes still surrounding by granuolosa cells

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Releases the ovum in less than 5 seconds

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May be blocked by prostaglandin inhibitors

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Occurs 36hrs after the LH peak

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Occurs 32hrs after injection of HCG

Regarding placenta

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Exchange of oxygen & nutrients occurs in tertiary villi

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HCG is the first hormone released by placenta

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It is a source of haematopoietic stem cells of the faetus

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Its villous capillaries are branches of the uterine artery

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It receives blood supply from uterine artery only

Allantois is

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An endodermal derivative

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Converted to urachus

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An axis for the development of the umbilical cord

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Continuous with the anal canal

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A cranial diverticulum of yolk sac

Placental barrier is composed of

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Syncytiotrophoblast

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Cytotrophoblast

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Endothelium of fetal blood vessels

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Amniotic membrane

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Decidua

Placental barrier

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Becomes a double layered membrane in late pregnancy

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Becomes thinner as villi lose their cellular and connective tissue surrounding the capillaries

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Is exclusively composed of maternal tissue

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Is composed of three layers in early stage

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Is a chorionic derivative

Following substances cross the placental barrier against concentration gradient

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Calcium

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Amino acid

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Iron

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Magnesium

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Fat soluble vitamin

Umbilical cord contains:

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Wharton's jelly

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Allantois

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One umbilical vein

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Two umbilical artery

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Yolk sac

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