Week 6 Holy - Fertilization, Early Development Flashcards

Question

What do the inner cells in a morula become?

Answer 1

Inner Cell Mass -eventually become the embryo proper

Answer 2

Trophoblast -later becomes extraembryonic tissues (including the placenta)

Answer 3

* tight junctions and gap junctions form (cadherins) * cells flatten together to form a tight ball * cells become more polarized (apical/basal surface)

Answer 4

_When_: 6-12 days after fertilization _Where_: Usually occurs on the superior posterior wall of the uterine cavity. (can occur at abnormal sites: abdominal cavity, ovary, or uterine tube)

Answer 5

Hydrolytic enzymes are released by the embryo that degrade the wall of the zona pellucida, allowing the blastocyte to squeeze out, or "hatch."

Answer 6

Abnormal implantation. Blastocyte implants in area other than uterine wall. ex. abdominal cavity, ovary, fallopian tube, ampulla

Answer 7

Implantation close to the mouth of the cervix, resulting in the placenta partially covering the cervical canal. -can cause hemorrhage during pregnancy and can threaten the survival of the fetus and mother

Answer 8

Inner cell mass flattens and forms a roughly circular disc, composed of two layers. - tall columnar cells closest to amniotic cavity = epiblast - underlying cuboidal cells = hypoblast

Answer 9

Cells in bilaminar disc closest to the forming amniotic cavity. - tall columnar cells - will eventually give rise to the embryo

Answer 10

Bottom layer of cells in the bilaminar disc. - cuboidal - Day 9: hypoblast cells enclose space called the primary yolk sac - will form extraembryonic structures

Answer 11

Thickening formed when epiblast cells migrate toward the midline of the embryonic disc. Demarcates the anterior-posterior and left-right axies of the embryo. (primitive groove = valley where epiblast cells fold under in primitive streak)

Answer 12

Thickening of cells at the cranial end of the primitive streak. -cells migrate rostrally and form a thick cord of cells called the notochord (inductive force in cell specialization and development)

Answer 13

* Central and peripheral nervous system * epidermis * sensory epithelium of ear, nose, & eye * pituitary, sebaceous, and mammary glands * hair, nails, cutaneous glands

Answer 14

* epithelium of the lung * GI tract * bladder * liver * pancreas

Answer 15

* Paraxial * muscles of head, trunk, limbs, axial skeleton, dermis, connective tissue * Intermediate * urogenital system (gonads) * Lateral * connective tissue and muscle of viscera, heart and blood cells * serous membranes of pleura * pericardium * peritoneum

Answer 16

1. lends longitudinal mechanical support to the embryo 2. serves as a powerful inductive force on the subsequent differentiation of many cell types (prime inducer of nervous system development) (eventually the vertebral column forms around the notochord)

Answer 17

Inner Cell Mass

Answer 18

Amnion, yolk sac, and allantois

Answer 19

Trophoblast = outer cells in blastocyst * Cell proliferation and invasion into uterine wall * Forms outer layer of placenta * Divided into two layers: overylying Syncytiotrophoblast & underlying Cytotrophoblast \*\*\*I don't know\*\*

Answer 20

thick cord of cells called that have inductive force in cell specialization and development

Answer 21

The first stage of nervous system formation occurs when epiblast (ectoderm) cells directly overlying the notochord are induced by the notochord to proliferate and to form a thickening called the neural plate.

Answer 22

Areas of the neural plate that buckle and curve around to form a tube.

Answer 23

Tube completely enclosed by ectoderm

Answer 24

Cells detach from the neural tube and actively begin to migrate within the embryo mesoderm.

Answer 25

* Spinal/autonomic/cranial nerve ganglia * Schwann cells * meninges * melanocytes * adrenal medulla * some craniofacial muscles of the head

Answer 26

EMT epithelial cells lose their cell polarity and cell-cell adhesion, and gain migratory and invasive properties to become mesenchymal stem cells; these are multipotent stromal cells that can differentiate into a variety of cell types

Answer 27

MET reversible biological process that involves the transition from motile, multipolar or spindle-shaped mesenchymal cells to planar arrays of polarized cells called epithelia. MET is the reverse process of epithelial–mesenchymal transition (EMT)

Answer 28

Blastomeres initially have similar development potencies, each capable of giving rise to a complete embryo. The process of differentiation is responsive to environmental signals, which allows the developmental program to respond and adjust to various types of perturbations.

Answer 29

Cell fate is already assigned during cleavage, and a strict developmental plan is in place, whereby removal of one or more cells results in an incomplete embryo. Cell fate is usually determined by the differential inheritance of specific factors among daughter cells during cell divisions, in a process called asymmetric cell division.

Answer 30

Cells of early embryos fail to adhere together normally, and fall apart. * Splitting can occur in: * 2-cell embryo → 2 blastocysts, 2 amnions, 2 chorions * blastocyst inner cell mass → 2 amnions, 1 chorion * after trophoblast formation → 1 amnion, 1 chorion

Answer 31

Totipotent cells can give rise to ALL embryonic and extra-embryonic cell types and structures.

Answer 32

Pluripotent cells can give rise to all embryonic cell types and structures, but not extraembryonic stuff.

Answer 33

Multipotent cells can give rise to multiple (but not all) cell types.

Answer 34

Unipotent cells can give rise to just one type of cell.

Answer 35

The process were one cell or group of cells changes the developmental fate of another group. * defined by distances between cells * Paracrine * Juxtacrine * Autocrine * defined by the behavior of cells * instructive * permissive * cells producing signals are the inducers

Answer 36

A substance governing the pattern of tissue development in the process of morphogenesis and the positions of the various specialized cell types within a tissue. \*More precisely, a morphogen is a signaling molecule that alters cell fate.

Answer 37

* Paracrine * involves diffusable molecules * Juxtacrine * involves cell-cell contact * Autocrine * cells stimulate themselves

Answer 38

Cells close to inducer receive greater amounts of signaling factors than cells farther away.

Answer 39

Inducer (agonist) secretes signaling factors and cell opposing inducer (antagonist) sends out inhibitory signal.

Answer 40

Inducer secretes signaling factor to nearby cells which in turn send out different signaling factor to nearby cells, which causes those cells to release signaling factors, and so on.

Answer 41

Two (or more) signals are combined to form a third composite signal, which has a different effect than the two individual signals.

Answer 42

* Notochord induces the ventral floor plate to secrete **sonic hedgehog** (Shh) * Overlying ectoderm induces the dorsal roof plate to secrete BMP * The opposing gradients formed instruct the cells in between to express transcription factors (Pax6, Pax7, and NKx6.1) and adopt specific fates

Answer 43

* Ciliary cells of the primitive node establish directional fluid flow from right-to-left * by all beating in same direction (counterclockwise/leftward) * bended cilia is thought to open Ca²⁺ channels * Increases the expression of the signaling molecule "Nodal" on the left side of embryo * stimulates production of itself and "Lefty" * antagonist to Nodal * Nodal also stimulates transcription factor "Pitx2"

Answer 44

* Homeobox (Hox) genes arranged in the same general order on the chromosome as the anterior-posterior axis * encode for transcription factors that contain homeodomains (a DNA-binding sequence of 60 AA's) * regulated by retinoic acid which can disrupt normal patterns of Hox gene expression

Answer 45

* Patched protein binds to and inhibits smoothened protein * allows PKA and Slimb to cleave GLI protein * GLI acts as a repressor and no transcritption of Hedgehog-responsive genes occurs * Hedgehog binds to Patched protein which activates smoothened protein * smoothened inhibits PKA and Slimb * uncleaved GLI enters nucleus and activates transcription of Hedgehog-response genes

Answer 46

* Condition due to defective Hedgehog signaling * trouble defining midline structures * one eye, closely spaced eyes * single-nostril * midline cleft * single central upper incisor

Answer 47

1. Transforming Growth Factor (TGF) pathway 2. Hedgehog pathway 3. Fibroblast Growth Factor (FGF) pathway 4. Wnt Pathway 5. Notch Pathway

Answer 48

* TGF-beta Superfamily (Activin, TGF-beta, BMP, and Nodal proteins) ligands * Ligand → Receptor II (becomes active) * Receptor II → Receptor I → Smad activation → Smad dimerization → Smad4-P acts as transcription factor (transcription or repression) \*Mesoderm & endoderm; osteogenesis; L-R asymmetry

Answer 49

* Fibroblast Growth Factor (FGF) and Epidermal Growth Factor (EGF) = ligands * RTKs, FGFR, & EGFR = receptors * RTK → GNRP → Ras → MAP kinase cascade → activated transcription factor → stimulates gene expression

Answer 50

* Ligand = Wnt * Receptor = Frizzled * Wnt → Frizzled → active Disheveled inhibits glycogen synthase kinase 3 (GSK-3) → releases and inhibits destruction of beta-catenin → beta-catenin associates with LEF/TCF to become an active transcription factor \*intestinal crypt stem cells, hematopoiesis, neural crest

Answer 51

* Ligand = Delta * Receptor = Notch * Delta → Notch → activate protease to cleave Notch → enters the nucleus → Notch activates transcription factor CSL \*\*Hematopoiesis, neural development, somitogenesis

Answer 52

* cell migration is a fundamental part of morphogenesis * Epithelial-to-mesenchymal transitions (EMT) and Mesenchymal-to-epithelial transitions (MET) are important events in embryogenesis * EMT: regulated by TGF-b, FGF, Wnt, & Notch * MET: regulated by BMP * Signaling pathways activate the expression of transcription factors like "Snail" * regulate genes involved in motility and adhesion

Answer 53

* Selective cell-cell adhesion is mediated by cadherins that are expressed in tissue-specific patterns * stop expressing cadherin → break free * expression of particular cadherins will dictate where/what cell binds to * Cells expressing different cadherins can "sort out" or "re-aggregate"

Answer 54

* Common key features include: * Activation of TGF-b, Wnt, or RTK signaling pathways * Activation of specific transcription factors (especially Snail family) * Changes/inhibition of cadherin expression * Modification of the extracellular matrix by matrix metalloproteinases * Use of pre-existing tissue structures to guide motility

Answer 55

1. Stem cells can self-renew in order to sustain long-term tissue regeneration 2. Stem cells are not terminally differentiated, but can give rise to daughter cells that can terminally differentiate

Answer 56

Movement of an organism in response to a chemical stimulus. Somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment.

Answer 57

* Stem cells: * divide indefinitely * Progenitor cells: * divide a finite number of times * Terminal differentiated cells: * unable to differentiate further * some able to regain proliferative potential

Answer 58

* Use of progenitor cells as an amplifying system keeps the number of stem cells that are needed low * number of divisions they need to make is much reduced → reducing the potential for genetic damage * Segregate their replicated chromosomes so that the daughter cell that remains a stem cell receives all of the parental chromosome template strands * this is called "immortal strand hypothesis"

Answer 59

* Stem cells are the reserve cells that are used to replenish tissues and organs. * respond to tissue/organ needs

Week 6 Holy - Fertilization, Early Development Flashcards

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