Embryology Flashcards

1
Q

Germinal Stage is from week ___ to ___

A

Germinal stage– week 1 to 2

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2
Q

The zygote (diploid) will multiply to form the _________

A

Morula– ball of about 8 cells

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3
Q

Morula becomes the ________

A

Blastula– bundle of cells containing an inner cavity known as the blastocoel

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4
Q

Implantation

A

Blastula fuses with the uterine wall (endometrium)

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5
Q

Blastula develops into the ________ and __________ after implantation

A

Embryoblast
- inner cell mast which will form the majority of the EMBRYO

Trophoblast
- outer cell mass that will mainly become the PLACENTA

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6
Q

During week 2, the embryo blast forms a _________ _____

A

Bilaminar disc

2 parts:
- epiblast: becomes 3 major germ layers
- hypoblast: little importance, mostly disappears

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7
Q

Amniotic Cavity and Yolk Sac Cavity

A

Visible in week 2

Amniotic cavity encases the fetus as it develops

Yolk sac cavity is responsible for nutrient and gas exchange before the placenta is developed enough to do this

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8
Q

Caudal Midline

A

Can be identified on dorsal aspect of embryo by locating the primitive node and primitive streak

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9
Q

Gastrulation

A

Week 3

3 distinct germ layers can be seen– ectoderm, mesoderm, and endoderm

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10
Q

Ectoderm

A

Forms epidermis, facial skeleton, nervous system

Forms teeth
- enamel derived from surface ectoderm
- majority of tooth derived from neural crest cells

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11
Q

Mesoderm

A

Forms “structural components” of the body like the skeletal system, muscular system, and connective tissue

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12
Q

Endoderm

A

Forms the lining of the foregut, midgut, and hindgut

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13
Q

Neurulation

A

Week 4

Neural plate folds in on itself and forms the neural tube

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14
Q

Notochord

A

Derived from mesoderm, signals the start of neurulation

Forms the vertebral column

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15
Q

Neural plate

A

Ectodermal tissue

Folds into the neural groove

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16
Q

Neural fold

A

Joining of the neural plates on either side of the neural plate

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17
Q

Neural groove

A

inner pouch that forms as the neural plate pinches in

18
Q

Neural tube

A

Tube-like structure that sits below the remaining ectodermal layer (soon to be epidermis)

19
Q

Neural crest

A

Former ends of the neural fold

Neural crest cells migrate throughout the embryo and form various specialized structures (ex. glia, melanocytes)

20
Q

As neurulation ends, _______ ______, ________ ________, and __________ begin to form cranially to caudally.

A

aortic arches
pharyngeal arches
somites

21
Q

Buccopharyngeal membrane

A

opens cranially

Forms stomodeum: primitive oral cavity

22
Q

Blastopore

A

primitive anus, located caudally

23
Q

Optic placode

A

Primitive eye

24
Q

Otic placode

A

Primitive ear

25
Q

Pharyngeal Arches

A

Visible outpouchings that are precursors to various head and neck structures

There are 6 arches total, but arch 5 does not derive any structures

6th arch is located deep within the embryo and is not visible

Distinct anatomical features
- endodermal pouch
- mesenchymal core (mesoderm, neural crest, artery, nerve, muscle, cartilage)
- external ectodermal cleft

26
Q

Pharyngeal Arch I (Mandibular)

A

Many structures are associated with the mandible and anterior ear

27
Q

Pharyngeal Arch II (Hyoid)

A

Many structures associated with posterior ear and regions on an axis moving anteroinferiorly

28
Q

Pharyngeal Arch III

A
29
Q

Pharyngeal Arch IV

A

“Adams Apple cartilage”

CN X muscles of deep pharyngeal region

30
Q

Pharyngeal Arch VI

A

Most Inferior cartilage before trachea

31
Q

Pharyngeal clefts

A

Grooves on the ectodermal side between adjacent pharyngeal arches

Any issues in pharyngeal cleft formation results in brachial cyst

32
Q

Pharyngeal Pouches

A

Grooves found on the endodermal side between pharyngeal arches

If pharyngeal pouches fail to develop correctly, brachial fistulas may result

33
Q

Arch I placode, cleft and pouch

A

placode: trigeminal ganglion (CN V)

cleft: external auditory meatus

pouch: Eustachian tube and tympanic cavity

34
Q

Arch 2 placode, cleft, and pouch

A

placode: geniculate ganglion (CN VII)

cleft: cervical sinus

pouch: palatine tonsil

35
Q

Arch 3 placode, cleft, and pouch

A

placode: inferior sensory ganglion (CN IX)

cleft: cervical sinus

pouch: thymus and inferior parathyroids

pouch derivatives eventually migrate inferiorly by the lungs

36
Q

Arch 4 placode, cleft, and pouch

A

placode: inferior sensory ganglion (CN X)

cleft: cervical sinus

pouch: superior parathyroids and ultimobranchial body (parafollicular cells)

pouch derivatives eventually migrate inferiorly by the lungs but remain superior to arch 3 pouch

37
Q

Pituitary Gland Derivation

A

Roof of oral cavity (stomodeum) forms an invagination superiorly– Rathke’s Pouch
- forms ANTERIOR pituitary
- oral ectodermal origin

Floor of forebrain (diencephalon) evaginates inferiorly
- forms POSTERIOR pituitary gland
- neural ectodermal origin

38
Q

Thyroid Derivation

A

Derived from tissues at the tongues base, specifically a depression known as the foramen cecum

Thyroglossal duct allows for temporary connection of the foramen cecum of the tongue and the thyroid gland

LINGUAL THYROID– may be present at base of patient’s tongue if the thyroid did not descend properly during development

39
Q

Lip Derivation

A

Nasal pits surrounded by lateral nasal prominence and medial nasal prominence

Maxillary prominence is lateral and inferior, and moves ventrally and medially
- forms cheeks and lateral upper lip
- medial nasal prominences fuse together– form crest and tip of nose and philtrum

Mandibular prominence contributes to the jaw and lower lip

CLEFT LIP– failure of the medial nasal prominence and maxillary prominence to fuse

40
Q

Palate Derivation

A

Primary palate = philtrum of lip, forms via fusion of 2 medial nasal prominences… 4 maxillary incisors grow here

Palatine shelves– move caudally and medially

Week 7– tongue moves inferiorly into oral cavity through palatine shelves
- now the palatine shelves can move horizontally and medially to fuse at midline (fuse cranial-to-caudal)

Secondary palate– fusion of the palatine shelves

Incisive foramen = fusion of primary and secondary palates at the midline

INCOMPLETE CLEFT PALATE= failure of palatal shelves to fuse

COMPLETE CLEFT PALATE= failure of primary palate to fuse with palatal shelves

41
Q

DiGeorge Syndrome

A

Developmental disorder (genetic or environmental)

AKA third and fourth pouch syndrome

Affects neural crest cells, 3rd and 4th pharyngeal pouches (thymus and parathyroid gland development severely impacted)

“CATCH 22”
- Cardiac abnormalities
- Abnormal facies (hypertelorism, short philtrum, small mandible)
- Thymus aplasia
- Cleft palate
- Hypocalcemia (lack of PTH via parathyroid)
- 22q11 deletion