Human Embryogenesis

Question 1

Embryonic period lasts from weeks - and is marked by ____ and ___ teratogen susceptibility

Fetal period lasts from weeks - and is marked by ____, ____, and ____, and ___ teratogen susceptibility

Answer 1

Embryonic period lasts from weeks 3-8 and is marked by ORGANOGENESIS and HIGH teratogen susceptibility

Fetal period lasts from weeks 9-38 and is marked by DIFFERENTIATION, GROWTH, and WEIGHT GAIN, and LOWER teratogen susceptibility

Question 2

Fertilization occurs in the the ____.

An oocyte that is not fertilized within 24 hours of ovulation, it _____.

The ovary’s ___ ___ secretes _____ that prepare _____ for ____.

Answer 2

Fertilization occurs in the the AMPULLA.

An oocyte that is not fertilized within 24 hours of ovulation, it DEGENERATES.

The ovary’s CORPUS LUTEUM secretes HORMONES that prepare ENDOMETRIUM for IMPLANTATION.

Question 3

Oocyte’s Layers:
-Corona radiata/____ _____: consists of ____ cells, which provides ____, ____ and ____ for the oocytes. Also contains ____ for sperm.

• Zona pellucida: _____ layer, made up of _____. ___ binds sperm.
• Plasma membrane

Answer 3

Oocyte’s Layers:
-Corona radiata/CUMULUS OOPHORUS: consists of FOLLICULAR cells, which provides PROTECTION, ENERGY and SUPPORT for the oocytes. Also contains CHEMOATTRACTANTS for sperm.

• Zona pellucida: GLYCOPROTEIN layer, made up of ZPs. ZP3 binds sperm.
• Plasma membrane

Question 4

Process of Capacitation

• _____ are removed from tip of sperm head to make the membrane overlying the ____ more ____ for ___ release during fertilization.
• There are also modifications in sperm ____ ____ and their ____ become ________ and more ____ in order to penetrate the _____ _____.

Answer 4

Process of Capacitation

• GLYCOPROTEINS are removed from tip of sperm head to make the membrane overlying the ACROSOME more FLUID for ENZYME release during fertilization.
• There are also modifications in sperm INTRACELLULAR SIGNALING and their TAILS become HYPER-ACTIVATED and more MOTILE in order to penetrate the CORONA RADIATA.

Question 5

Phases Of Fertilization:

• ____ sperm penetrate the _____ via _____ ____
• sperm heads bind _____ receptors in ___ ____ and release _____ ____ that ____ the ____ ____.
• oocyte and sperm plasma membranes fuse, and oocyte completes _____, resulting in _____ and ____. Formation of ____

Answer 5

Phases Of Fertilization:

• CAPACITATED sperm penetrate the ZONA RADIATA via WHIPPING TAILS
• sperm heads bind ZP3 receptors in ZONA PELLUCIDA and release ACROSOMAL ENZYMES that PENETRATE the ZONA PELLUCIDA.
• oocyte and sperm plasma membranes fuse, and oocyte completes MEIOSIS II, resulting in HAPLOID GAMETE and POLAR BODY. Formation of ZYGOTE

Question 6

Oocyte’s Block To Polyspermy

• upon sperm contact with oocyte’s _____, the ______ _____.
• there is an intracellular ___ tsunami that induces the _____, where ___ granules will be exocytosed to modify the ____ ____ to prevent more entry of sperm.

Answer 6

Oocyte’s Block To Polyspermy

• upon sperm contact with oocyte’s PLASMA MEMBRANE, the MEMBRANE DEPOLARIZES.
• there is an intracellular CALCIUM tsunami that induces the CORTICAL REACTION, where CORTICAL granules will be exocytosed to modify the ZONA PELLUCIDA to prevent more entry of sperm.

Question 7

Difference between MZ and DZ Twins:
-DZ: 2 oocytes are ovulated and fertilized by separate sperm. Their amniotic cavity is ____ and their placenta may be ____ or ____.

• MZ: A single oocyte is fertilized by a single sperm and zygote splits into 2 within _____ after fertilization.
  - early split = ____ stage
  - late split= _____ stage
• amniotic cavity is separate in ____ split, shared in ___ split
• placenta is separate in ____ split, shared in ___ split

Answer 7

Difference between MZ and DZ Twins:
-DZ: 2 oocytes are ovulated and fertilized by separate sperm. Their amniotic cavity is SEPARATE and their placenta may be SEPARATE or FUSED.

• MZ: A single oocyte is fertilized by a single sperm and zygote splits into 2 within ONE WEEK after fertilization.
  - early split = TWO-CELL stage
  - late split= BLASTOCYST stage
• amniotic cavity is separate in EARLY split, shared in LATE split
• placenta is separate in EARLY split, shared in LATE split

Question 8

Cleavage is a series of _____ mitotic divisions during week ___. These divisions occur ~__ hrs apart and result in _____.

These ____ get ____ with each successive division and are encased by ____.

_____ up through the 8-cell stage are totipotent.

Answer 8

Cleavage is a series of SYMMETRICAL mitotic divisions during week ONE. These divisions occur ~20 hrs apart and result in BLASTOMERES.

These BLASTOMERES get SMALLER with each successive division and are encased by ZONA PELLUCIDA.

BLASTOMERES up through the 8-cell stage are totipotent.

Question 9

By day __, the 32-cell ____ is a ___ ball of compacted cells migrating in the _______. The cells of the ____ establish ____; ICM=______ and OCM=_____

Answer 9

By day FOUR, the 32-cell MORULA is a COMPACTED ball of compacted cells migrating in the FALLOPIAN TUBE. The cells of the MORULA establish POLARITY; ICM=EMBRYOBLAST and OCM=TROPHOBLAST

Question 10

Fluid from the uterine cavity penetrates the ___ ____ to surround cells of the morula’s _____. By ___ days, the penetrating fluid pools and forms the _____ cavity of the ____.

Answer 10

Fluid from the uterine cavity penetrates the ZONA PELLUCIDA to surround cells of the morula’s ICM. By 4.5 days, the penetrating fluid pools and forms the BLASTOCYST cavity of the BLASTOCYST.

Question 11

Implantation:
-at ~_ days after fertilization, ____ implantation occurs during ___ phase of the endometrium (add __ days to day 14, when fertilization needed to occur to get the day # for ____ phase)

• _____ drive implantation. They secrete _____ that degrade the ___ ____ and the ____ hatches through the ____ ____ on day _.
• The ____-____-free ___ implants into endometrium as ______ embed into the uterine wall and eventually form ____ components of the placenta.
• ______ secrete _____, which induces the ___ ___ to continue secretion of _____ for endometrium maintenance.
• With implantation, the endometrium undergoes as _____ reaction with increased ____ activity.

Answer 11

Implantation:
-at ~6 days after fertilization, BLASTOCYST implantation occurs during SECRETORY phase of the endometrium (add 6 days to day 14, when fertilization needed to occur to get the day # for SECRETORY phase)

• TROPHOBLASTS drive implantation. They secrete ENZYMES that degrade the ZONA PELLUCIDA and the BLASTOCYST hatches through the ZONA PELLUCIDA on day 5.
• The ZONA PELLUCIDA-free BLASTOCYST implants into endometrium as TROPHOBLAST embed into the uterine wall and eventually form FETAL components of the placenta.
• TROPHOBLAST secrete hCG, which induces the CORPUS LUTEUM to continue secretion of PROGESTERONE for endometrium maintenance.
• With implantation, the endometrium undergoes as DECIDUA reaction with increased GLANDULAR activity.

Question 12

Week Two Of Pregnancy:

• the _____ of the blastocyst forms the ________
• the cells on the dorsal side are _____ and ventral to those are _____. They both comprise the _____. Dorsal to the ____ is the ________, and ventral to the _____ is the _____.

Answer 12

Week Two Of Pregnancy:

• the EPIBLASTS of the blastocyst forms the BILAMINAR DISC
• the cells on the dorsal side are EPIBLASTS and ventral to those are HYPOBLASTS. They both comprise the BILAMINAR DISC. Dorsal to the DISC is the AMNIOTIC CAVITY, and ventral to the DISC is the YOLK SAC.

Question 13

Name 4 Extraembryonic Structures

Answer 13

• amniotic cavity
• yolk sac
• connecting stalk
• fetal part of placenta

Question 14

Epiblasts differentiate into cells of the _____ and _____, which line the ____ ____ and secrete _____. The ____ will eventually surround the embryo.

Answer 14

Epiblasts differentiate into cells of the EMBRYO PROPER and AMNIOBLASTS, which line the AMNIOTIC CAVITY and secrete AMNIOTIC FLUID. The AMNIOTIC SAC will eventually surround the embryo.

Question 15

Hypoblasts proliferate and migrate to line the ___ _____ surface of the _____ ____ which becomes the _____ ____. It eventually regresses.

It’s functions are: ____ via ____ vessels

• early ______
• and brings _____ to gonads

Answer 15

Hypoblasts proliferate and migrate to line the INNER TROPHOBLAST surface of the BLASTOCYST CAVITY which becomes the YOLK SAC. It eventually regresses.

It’s functions are: EARLY EXCHANGE via VITELLINE vessels

• early HEMATOPOIESIS
• and brings GERM CELLS to gonads

Question 16

______ give rise to the tissue that makes up the connecting stalk. The connecting stalk becomes the _____ and connects the embryo to the ____.

Answer 16

HYPOBLASTS give rise to the tissue that makes up the connecting stalk. The connecting stalk becomes the UMBILICAL CORD and connects the embryo to the PLACENTA.

Question 17

Trophoblasts and _____-derived tissue contribute to formation of ________. The _____ part of the _____ develops from the trophoblast-altered ____.

Answer 17

Trophoblasts and HYPOBLAST-DERIVED TISSUE-derived tissue contribute to formation of FETAL PART OF PLACENTA/CHORION FRONDOSUM. The MATERNAL part of the PLACENTA/DECIDUA BASALIS develops from the trophoblast-altered ENDOMETRIUM.

Question 18

Umbilical cord is made up of:
______ and _____,
The ___ carry deoxygenated blood from ____ and ____ carries nutrient-rich/oxygenated blood

-the capillaries are covered in _____

Answer 18

Umbilical cord is made up of:
TWO UMBILICAL ARTERIES and ONE UMBILICAL VEIN,
The ARTERIES carry deoxygenated blood from FETUS and VEIN carries nutrient-rich/oxygenated blood

-the capillaries are covered in TROPHOBLASTS, to prevent mixture of fetal and maternal blood

Question 19

During week 3 of pregnancy, the bilaminar embryo forms the ____ via ____, which occurs with ____ ____ formation in the ____ side of the ____ of the bilaminar disk

Answer 19

During week 3 of pregnancy, the bilaminar embryo forms the TRILAMINAR DISC via GASTRULATION, which occurs with PRIMITIVE STREAK formation in the CAUDAL/DORSAL side of the EPIBLAST of the bilaminar disk

Question 20

Primitive Streak Formation:

-____ cells migrate to the primitive streak where they ____ and _____, causing ____.

Answer 20

Primitive Streak Formation:

-EPIBLAST cells migrate to the primitive streak where they DETACH and INVAGINATE, causing GASTRULATION.

Question 21

Details of Gastrulation Layers:
-Epiblast cells that intercalate among ____ cells displace and completely replace _____ cells to form ____.

• Epiblast cells that settle between the ____ and epiblast form ____, which migrate ____ and ____.
• Epiblast cells that remain behind are _____.
• Some epiblasts at the streak have ___, which can generate a ___ which will cause ____-____ ____ of embryo.

Answer 21

Details of Gastrulation Layers:
-Epiblast cells that intercalate among HYPOBLAST cells displace and completely replace HYPOBLAST cells to form ENDODERM.

• Epiblast cells that settle between the ENDODERM and epiblast form MESODERM, which migrate LATERALLY and CRANIALLY.
• Epiblast cells that remain behind are ECTODERM.
• Some epiblasts at the streak have CILIUM, which can generate a CURRENT which will cause LEFT-RIGHT POLARITY of embryo.

Question 22

Germ Layer Facts:
-Ectoderm makes up: ____, ____, ____, and some ____

• Mesoderm makes up: ___, ____, ____, ____, and ____
• Endoderm makes up: ____, ____, and some ____

Answer 22

Germ Layer Facts:
-Ectoderm makes up: NERVOUS SYSTEM, EPIDERMIS, SENSORY RECEPTORS, and some GLANDS.

• Mesoderm makes up: SKELETAL, MUSCULAR, UROGENITAL, CARDIOVASCULAR SYSTEMS, and SEROSA
• Endoderm makes up: EPITHELIA OF URINARY BLADDER, GI-RESPIRATORY SYSTEMS, and some GLANDS.

Question 23

Ectoderm-Endoderm Membranes are found:
- ______ membrane at ___ end of embryo, future location of _____.

• ____ membrane at ___ end of embryo, future location of _____.
• both areas are _____

Answer 23

Ectoderm-Endoderm Membranes are found:
- BUCCOPHARYNGEAL membrane at CRANIAL end of embryo, future location of ORAL CAVITY.

• CLOACAL membrane at CAUDAL end of embryo, future location of ANUS.
• both areas are AVASCULAR

Question 24

When primitive streak fails to regress by the __ week as the ____ ___ forms, ____ will form, and they contain tissues derived from ____ ____ cells.

Answer 24

When primitive streak fails to regress by the THIRD week as the NOTOCHORD MESODERM forms, TERATOMAS will form, and they contain tissues derived from PLURIPOTENT EPIBLAST cells.