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Embryology > embryo annexes > Flashcards

embryo annexes Flashcards

1
Q

what are the embryo annexes

A
  1. yolk sac
  2. amnion
  3. allantois
  4. umbilical cord
  5. chorion
  6. placenta
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2
Q

what is the function of the yolk sac

A

-hematopoiesis
-angeiogenesis
-gonocyte development
-forms primitive intestine

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3
Q

Process of cell formation stemming from the yolk sac

A

Cells are derived from the extraembryonic mesoderm of the VS wall (also called the islets of Wolff)

HEMOPOIESIS: cells become rounded, globular forming RBCs

ANGIOGENESIS: cells become flattened squamous forming vessel endothelium

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4
Q

when does the development of gonocytes occur

A

-primordial germ cells originate in embryo after 21 days in the YS wall

-migration of primordial cells occurs in week 5 in the genital ridges, causing them to priloferate

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5
Q

function of the amnion

A
  1. shock absorber
  2. allows embryo movement and development of MS system
  3. thermoregulation
  4. barrier to infections and contains fetal urine
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6
Q

Allantois def

A

the sac like structure in the embryo connecting stalk, lined by the endoderm

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7
Q

characteristic of the allantois in humans

A

RUDIMENTARY:
one portion regresses and another forms URACHUS (cord connecting umbilical region with the urinary bladder)

the part that regresses is replaced by CT –> Wharton’s jelly (mucous loose CT) contains allantois remnants

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8
Q

What is the blood vessel system of the umbilical cord

A

contains 2 arteries and 1 vein –> flow mirrors pulmonary circulation bcos it is different in its movement and contents:

ARTERIES: flow from embryo to the placenta: contain CO2, waste and deoxygenated blood

VEINS: flow from placenta to the embryo: contain nutrients and oxygenated blood

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9
Q

what is the advantage of umbilical cord post birth

A

can be stored bcos it contains hematopoietic cells within its blood vessels

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10
Q

what is the shape of the placenta

A

DISCOIDAL: thicker in the center an thinner in the lateral periphery

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11
Q

functions of placenta

A

Exhange of material between maternal and fetal circulation - FILTER

(includes: delivery of nutrients/ O2/antibodies, hormones, and the removal of waste products)

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12
Q

what are the placenta components

A
  1. EMBRYONIC COMPONENT: chorion forming the chorionic villi (STB, STB, EEM)
  2. MATERNAL COMPONENT: decidua basalis - the endometrium during pregnancy rich in glycolipids and lipids
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13
Q

Stages of development of chorionic villi

A

PRIMARY: 10/11 days, made of the first protrusions of the STB/ CTB membranes

SECONDARY: EEM grows and becomes incorporated into villi causing enlargement

TERTIARY: same as secondary but with blood vessels from the mesoderm extending into the vili

!! increase in size from primary to secondary

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14
Q

what would you see in a cross section of the 3 types of villi

A

primary: outer STB and inner CTB

secondary: outer STB, middle CTB and inner EEM

tertiary: same as secondary but the central EEM would contain blood vessels

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15
Q

what is present within the intervillus space

A

maternal blood supply (from the blood vessels) for contact with maternal circulation

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16
Q

Structure of the decidua

A

mucosa of the uterus during pregancy period having 3 REGIONS:

  1. decidua basalis (connects with villi to form the definitive placenta)
  2. decidua capsularis (capsule of the embryo)
  3. decidua parietalis (no contact with villi or embryo)
17
Q

what happens to the three layers of the decidua over the course of the pregnancy

A
  1. D basalis forms the definitive placenta by connecting to the chorionic villi
  2. Fusion of the D capsularis nad parietalis to form the DECIDUA VERA (expelled during delivery)
18
Q

Parts of the chorion

A

VILLOUS CHORION: region that has villi

SMOOTH CHORION: region that is absent of villi

19
Q

Special chacteristics of the villi in the placenta

A
  1. CBT SHELLS: proliferation of the CBT to form anchoring regions to the D basalis
  2. Intravillous space containing the maternal blood that comes in contact with the wall of the villi for exchange and transport
20
Q

How can we use embryo annexes to analyse the genetic profile of the embryo (2)

A

ANIOSCENTESIS: 14-18 weeks of pregnancy, transabdomical needle insertion into the amniotic cavity and extraction + analysis of amniotic fluid –> cells need culturing to stimulate proliferation

CVS (CHORIONIC VILLUS SAMPLING): 10-12 weeks of pregnancy, transvaginal needle insertion into placental mass and collection of villus cells.

21
Q

Pressure in the diff components of the placenta

A

BASED ON BLOOD PRESSURE DIFFERENCES

70-80 mmHg in arteries of decidua
20-30 mmHg in the vein of embryo
8mmHg in the vein of decidua

22
Q

how does placenta circulation work ()

A
  1. High blood pressure in arteries of decidua pushes maternal blood into the villus space in close proximity to embryo capillaries -> nutrient exchange
  2. Veins have lower blood pressure which favours entrance of blood back into the decidual veins from villus space -> waste product removal
23
Q

what changes occur in placenta during the 3rd trimester and why (3)

A

REASON: increases the efficiency of the transport of tissue

  1. CBT dissapears and only a few cells remain
  2. STB decreases in thickness
  3. Dilation of capillaries in intervillus space
24
Q

What is the disadvantage of the filter action of the placenta

A

toxins, drugs, alcohol, medication and some pathogens (HIV/syphillis) can also pass into the fetal circulation from the maternal which harms the baby

25
Q

Action of the placenta as an endocrine gland (4)

A
  1. hCG - maintains the gravidic CL to keep producing progesterone
  2. progesterone - production after the gravidic CL has regressed
  3. relaxin: increases cervical dilation and flexibility of pelvis
  4. placental lactogen hormone -> preps the mammary glands for lactation
26
Q

types of twins, their shared structures and when cell division occurs

A
  1. DIZYGOTIC: cell separation occurs very early, separate amniotic sacs, chorions and placenta
  2. MONOZYGOTIC:

2.1 DIAMNIOTIC: division occurs at the level of the blastocyst (2 inner cell masses), shared placenta but separate chorions and amniotic sacs

2.2 MONOAMNIOTIC: division occurs past the blastocyst (1 inner cell mass): shared placenta AND amniotic cavities

Embryology (4 decks)

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