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Life Sciences > Introduction to Embryology > Flashcards

Introduction to Embryology Flashcards

1
Q

How long is the embryonic period and what does it accomplish?

A

0 - 8 weeks

Establishes organ systems

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2
Q

How long is the foetal period and what does it accomplish?

A

From 9 weeks to term

Growth and maturation of organ systems

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3
Q

What are the 6 stages of implantation / impregnation?

A
  1. Ovulation
  2. Fertilisation
  3. Cleavage
  4. Morula
  5. Blastocyst
  6. Implantation
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4
Q

What occurs during week 1?

A

Fertilisation takes place in uterine tube
Calculated from day 0 OR 2 weeks before last menstrual period
Union of genetic material in sperm and ovum
Formation stages = fertilisation to blastocyst

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5
Q

What is a blastocyst?

A

Three days after fertilisation, a normally developing embryo will contain about 6 - 10 cells. By the fifth or sixth day, the fertilised egg is known as a blastocyst - a rapidly dividing ball of cells

In vitro fertilisation, emryos will be cultured until this stage before being implanted into the mother

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6
Q

What are the different layers of a blastocyst and their purpose?

A

Inner group of cells becomes the embryo

Outer group of cells becomes trophoblast (placenta) - nourish and protect the embryo

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7
Q

What three key steps occur during week 2?

A

Zona hatching = shedding the zona pellucida (surrounding glycoprotein sphere fof blastocyst) which allows implantation on the uterine wall

Implantation = affixation to uterine wall

Bilaminar formation = formation of two layers of the inner cell mass, seperated by an extracellular basement membrane

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8
Q

What are the two layers called in the bilaminar?

A 
Epiblast = top layer
Hypoblast = bottom layer
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9
Q

Gastrulation occurs in week 3 of the embryonic period, what does this mean?

A

Epiblast reorganises into a multilayered and multidimmensial structure called the gastrula or trilaminar embryonic disc

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10
Q

What are the layers and components of the trilaminar embryo post-gastrulation and what will they develop into?

A

Ectoderm = outer layer (skin, brain, and spinal cord)

Mesoderm = middle layer (muscle, connective tissue, cardiovascular system, and kidney)

Endoderm = bottom layer (Lines visera and the organs of gastrointestinal tract)

Supported by newly formed cartilaginous rod called the notochord which will become the neural tube

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11
Q

In terms of the orofacial region, what is the fate of the 3 germ layers?

A

Endoderm = submandibular and sublingual glands

Mesoderm = Heart and vascular tissues, masticatory / expression muscles, bone, and other connective tissues

Ectoderm = Parotid gland, enamel, dentine, pulp, cranial nerves, and taste buds

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12
Q

How is the neural tube formed?

A

Day 19 = neural folds start pinching towards the midline of the embryo

Day 22 = Convergence of neural folds

Day 23 = Neural folds fused together to form neural tube

Day 24 = Anterior neuropore closes

Day 26 = Posterior neuropore closes

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13
Q

What occurs in week 4 of the embryonic period?

A

Caudal and ventral body folding / embryonic folding

This forms the basic physiological structure (head, butt etc) as well as internalises the gut endoderm (future respiratory and digestive tracts)

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14
Q

What are pharyngeal arches and what is their function?

A

The result of mesenchymal tissue (connective tissue) in the cranial region of the embryo

Precursors for many crucial structures eg msucles, cartilage / bone, cranial nerves, blood, vessels

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15
Q

What is the structure of the pharyngeal arches?

A

Arches are seperated by clefts (pharyngeal grooves) on the ectodermal surface and pockets (pharyngeal pouches) on the endodermal surface

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16
Q

What are examples of muscle structures formed from pharyngeal arch 1?

A 
Masticatory muscles
Mylohyoid
Anterior belly of digastric
Tensor tympani
TVP
17
Q

What are examples of cartilage / bone structures formed from pharyngeal arch 1 by invading neural crest cells?

A

Meckel’s cartilage (mandible)
Palatopterygoquadrate bar (part of sphenoid)
Malleus
Incus

18
Q

What is an example of a cranial nerve structure formed from pharyngeal arch 1 by invading neural crest cells?

A

Trigeminal nerve

19
Q

What are examples of blood vessels formed from pharyngeal arch 1?

A

Maxillary artery

External carotid artery

20
Q

What are examples of muscle structures formed from pharyngeal arch 2?

A

Facial expression
Posterior belly of digastric
Stylohyoid
Stapedius

21
Q

What are examples of cartilage / bone structures formed from pharyngeal arch 2?

A

Stapes
Part of hyoid
Temporal bones

22
Q

What is an example of a cranial nerve structure formed from pharyngeal arch 2?

A

Facial nerve

23
Q

What is an example of a blood vessel formed from pharyngeal arch 2?

A

Internal carotid

24
Q

What is an example of a mucle structure formed from pharyngeal arch 3?

A

Stylopharyngeus

25
Q

What is an example of a cartilage / bone structure formed from pharyngeal arch 3?

A

Part of hyoid

26
Q

What is an example of a cranial nerve structure formed from pharyngeal arch 3?

A

Glosspharyngeal

27
Q

What is an example of a blood vessel formed from pharyngeal arch 3?

A

Common carotid

28
Q

What is an example of a muscle structure formed from pharyngeal arch 4 and 6?

A

Intrinsic laryngeal and pharyngeal

29
Q

What is an example of a cartilage / bone structure formed from pharyngeal arch 4 and 6?

A

Larnyx cartilage

30
Q

What is an example of a cranial nerve structure formed from pharyngeal arch 4 and 6?

A

Vagus

31
Q

What is an example of a blood vessel formed from pharyngeal arch 4 and 6?

A

Arch of the aorta

32
Q

What are the 5 key processes in shaping the nose and mouth?

A 
Frontonasal Process (FNP)
Medial Nasal Process (MNP)
Lateral Nasal Process (LNP
Maxillary Process
Mandibular Process
33
Q

How does the face develop?

A

Day 24 = Presence of stomodeum (what will become the mouth) which is between the maxillary processes. FNP is above and mandibular process is below

Day 28 = Nasal placodes form and mouth starts forming where stomodeum was

Day 31 = Nasal placodes become the MNP, the LNP, and form nasal pits

Day 35 = Various fusions of processes to form the base of the face

Face is fully developed by week 10

34
Q

What processes form the nose?

A

Nasal septum = fused MNP
Alae = fused LNP
Bridge = FNP

35
Q

What processes for the lips?

A

Philtrum = fused MNP
Upper lip = fused maxillary processes and MNP
Lower lip = fused mandibular processes

36
Q

What is macrostomia / microstomia mouth and how is it formed?

A

A deformity making the mouth appear larger / smaller due to lateral clefts

Due to failure of fusion between maxillary and mandibular processes

37
Q

What are the different kinds of cleft lips and how do they form?

A

Unilateral / bilateral cleft lips = failure of fusion of MNP and maxillary process

Oblique facial cleft = failure of fusion of LNP and maxillary process

Median cleft lip = failure of fusion of MNP and MNP

Cleft lower lip = Failure of fusion of mandibular process and mandiular process

38
Q

How does the hard palate develop?

A

From week 7 - 10

Fusion of the palatal shelves with each other and with the nasal septum separates the nasal cavities from the oral cavity

The epithelial cells either undergo EMT or apoptosis to allow the fusion of the processes

Ossification of the palate starts at week 8, mid-palatal suture ossifies by around 12 - 14 years old

Life Sciences (28 decks)

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