1
Q
What process facilitates genetic exchange to form new life in sexual organisms?
A
Reproduction (conception → pregnancy → birth)
2
Q
What is the developmental term for the process transforming a zygote into an embryo?
A
Embryogenesis
3
Q
Define the term embryo in the context of human development.
A
Cell collection developing into a fetus within the female womb
4
Q
List the chronological stages of embryogenesis starting from fertilization.
A
- Fertilization (br) 2. Cleavage/Blastulation (br) 3. Implantation (br) 4. Gastrulation (br) 5. Neurulation (br) 6. Placentation
5
Q
What is the duration of the human embryonic period?
A
First 8 weeks post-fertilization
6
Q
Which physiological systems begin development during the first 8 weeks?
A
Circulatory (br) Excretory (br) Neurologic
7
Q
Define a zygote in terms of cellular fusion.
A
Single cell formed by egg + sperm fusion (Fertilization)
8
Q
What occurs during the cleavage stage of development?
A
Rapid cell division (12-24 hours post-zygote formation)
9
Q
Describe the physical structure of a blastula/blastocyst.
A
Hollow ball of cells surrounding a fluid-filled cavity
10
Q
Define cell differentiation in the context of embryology.
A
Cells move down a (usually) unidirectional path toward specific form/function
11
Q
Identify the two primary cell populations in a blastocyst.
A
- Trophoblast (outer shell) (br) 2. Inner cell mass (embryoblast)
12
Q
What is the eventual fate of the trophoblast layer?
A
Forms structures for uterine implantation
13
Q
Contrast the developmental fates of the embryoblast vs. the trophoblast.
A
Embryoblast: forms the embryo (br) Trophoblast: forms implantation/placental structures
14
Q
What is the functional significance of the zona pellucida disappearing?
A
Allows the blastocyst to grow and change shape
15
Q
Define the term pluripotent regarding the inner cell mass.
A
Ability to differentiate into any body tissue (muscle, brain, bone, etc.)
16
Q
The inner cell mass differentiates into which two layers during the second week?
A
Epiblast and Hypoblast (Bilaminar disc)
17
Q
What is the spatial relationship between the hypoblast and the epiblast?
A
Hypoblast: faces blastocoel (br) Epiblast: opposite side (faces amniotic cavity)
18
Q
Which cavity forms on the side of the hypoblast?
A
Primitive yolk sac
19
Q
Which cavity forms on the side of the epiblast?
A
Amniotic cavity
20
Q
Which layer of the bilaminar disc does NOT contribute to the embryo?
A
Hypoblast
21
Q
What is the primary morphological transformation during gastrulation?
A
Bilaminar germ disc → Trilaminar germ disc
22
Q
Identify the three definitive germ layers formed during gastrulation.
A
- Endoderm (innermost) (br) 2. Mesoderm (middle) (br) 3. Ectoderm (outer)
23
Q
What is the structural definition of a “germ layer”?
A
Cell layer that forms one of the body’s organizational “tubes”
24
Q
Which embryologic event establishes the body’s midline and bilateral symmetry?
A
Formation of the primitive streak (Day 16)
25
Exactly when does the first step of gastrulation (primitive streak formation) occur?
~ day 16
26
What biological symmetry classification applies to humans and is established by the primitive streak?
Bilateral symmetry (deuterostomes)
27
What is actually being observed physically when looking at the "primitive streak"?
Moving cells (invaginating from epiblast to form endoderm/mesoderm)
28
Describe the direction of primitive streak formation.
Caudal (anus end) → Rostral (head end)
29
How is the endoderm formed during gastrulation?
First epiblast cells to invaginate and displace/border the hypoblast
30
Which cells remain to form the ectoderm after invagination?
Epiblast cells bordering the amniotic cavity
31
Which embryonic stage determines the positioning of the developing offspring within the womb?
Gastrulation
32
What overarching anatomical concept does the text use to describe the basic human body plan?
An inner tube (digestive tract) surrounded by a series of outer tubes
33
Which germ layer serves as the precursor for the liver and pancreas?
Endoderm
34
What adult structures are derived from the embryonic endoderm?
Digestive tract lining (br) Liver/Pancreas (br) Lung portions (br) Abdominal cavity lining
35
What specific structure forms the epithelial lining of the middle ear cavity and auditory tube?
Endoderm
36
What specific structure forms the epithelial lining of the lower 2/3 of the vagina?
Endoderm
37
What specific structure forms the parenchyma of the tonsils, thyroid, and parathyroid glands?
Endoderm
38
Identify the three subdivisions of the primitive gut tube.
1. Foregut (br) 2. Midgut (br) 3. Hindgut
39
What adult structures are derived from the foregut?
Esophagus (br) Stomach (br) Duodenum (proximal) (br) Respiratory bud (lungs)
40
Which gut segment gives rise to the distal duodenum through the transverse colon?
Midgut
41
What are the derivatives of the hindgut?
Distal transverse colon (br) Descending/Sigmoid colon (br) Rectum
42
What happens to the connecting ends of the gut tube while the neural tube is closing?
Gut tube connects to the ectoderm to form the mouth and anus
43
Which embryologic membrane temporarily closes the cranial end of the primitive gut?
Oropharyngeal (buccopharyngeal) membrane
44
At what specific time does the buccopharyngeal membrane disappear?
Beginning of week 4
45
Which embryologic membrane temporarily closes the caudal end of the primitive gut?
Cloacal membrane
46
What happens to the cloacal membrane at week 7?
Divides into anterior urogenital membrane and posterior anal membrane
47
By what specific time is the posterior anal membrane absorbed?
Week 9
48
How does the embryologic origin of the Parotid gland differ from the Submandibular/Sublingual glands?
Parotid: Ectoderm (br) Submandibular/Sublingual: Endoderm
49
How does the embryologic origin of the Thyroid follicular cells differ from Parafollicular (C) cells?
Follicular cells: Endoderm (br) Parafollicular cells: Neural Crest
50
How does the embryologic origin of the upper anal canal differ from the lower third (below the pectinate line)?
Upper anal canal: Endoderm (br) Lower third: Ectoderm
51
How does the embryologic origin of the labia majora/outer minora differ from the inner labia minora?
Outer (majora/outer minora): Ectoderm (br) Inner minora: Endoderm
52
How does the embryologic origin of the urinary bladder trigone differ from the rest of the bladder?
Trigone: Mesoderm (br) Rest of bladder: Endoderm
53
What specific part of the male urethra is derived from Ectoderm?
Terminal (Glanular) part
54
What specific parts of the male urethra are derived from Endoderm?
Majority of urethra (EXCEPT posterior prostatic and glanular parts)
55
Which germ layer gives rise to the skeletal and muscular systems?
Mesoderm
56
List the major organ systems derived from the mesoderm.
Reproductive (br) Renal (br) Cardiovascular
57
Identify the four subdivisions of the mesoderm.
1. Axial (notochord) (br) 2. Paraxial (somites) (br) 3. Intermediate (urogenital) (br) 4. Lateral plate
58
What is the adult remnant of the embryonic notochord?
Nucleus pulposus (intervertebral discs)
59
Which mesodermal subdivision gives rise to somites?
Paraxial mesoderm
60
List the three derivatives of a somite.
1. Sclerotome (bone/cartilage) (br) 2. Myotome (muscle) (br) 3. Dermatome (dermis)
61
What is a myocele?
A slitlike cavity developed within each somite that is eventually occluded
62
What defines the embryonic Somite Period?
Days 20-30 (br) ~38 somite pairs form
63
How many total somite pairs develop by the end of week 5?
42-44 pairs
64
At what exact rate do somites appear sequentially during development?
3 pairs per day
65
How many somite pairs are in the occipital, cervical, thoracic, lumbar, sacral, and coccygeal regions?
4 occipital, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 8-10 coccygeal
66
What is the clinical use of counting somites?
Estimation of embryonic age
67
Which mesodermal layer forms the kidneys and gonads?
Intermediate mesoderm
68
What structures arise from the lateral plate mesoderm?
Heart (1st organ) (br) Blood vessels (br) Body wall (br) Organ muscle
69
What two layers combine to form the somatopleure (embryonic body wall)?
Somatic mesoderm + Embryonic ectoderm
70
What two layers combine to form the splanchnopleure (embryonic gut wall)?
Splanchnic mesoderm + Embryonic endoderm
71
What shape does the intraembryonic coelom initially form before becoming the body cavities?
Horseshoe-shaped cavity
72
What specific cell type lines the intraembryonic coelom?
Flattened epithelial (mesothelial) cells
73
The intraembryonic coelom divides into which three specific body cavities during the second month?
1. Pericardial cavity (br) 2. Pleural cavities (br) 3. Peritoneal cavity
74
Which specific muscles are NOT derived from the Mesoderm?
Musculature of the iris
75
Which GI organ is the major exception to the rule that internal organs are Endodermal?
Spleen (derived from Mesoderm)
76
What germ layer gives rise to Microglia, Kupffer cells, RBCs, and WBCs?
Mesoderm
77
What germ layer gives rise to the Dura mater?
Mesoderm
78
The central nervous system (brain/spinal cord) originates from which germ layer?
Ectoderm
79
Which germ layer forms the integumentary appendages (hair/nails)?
Ectoderm
80
Identify the three categories of ectoderm.
1. Surface ectoderm (br) 2. Neuroectoderm (CNS) (br) 3. Neural crest (PNS/others)
81
List the derivatives of the Surface Ectoderm (Mnemonic: LONE HEL STEEL).
Epidermis (br) Hair/Nails (br) Teeth enamel (br) Oral epithelium (br) Lens of eye (br) Exocrine glands
82
Identify the derivatives of the Neuroectoderm.
CNS neurons (br) Retina/Optic nerve (br) Pineal gland (br) Neurohypophysis (br) Glia (Astrocytes/Oligodendrocytes)
83
What embryologic structure attaches to the oral epithelium to form the Adenohypophysis (anterior pituitary)?
Rathke's pouch
84
Contrast the origin of the CNS vs. the PNS.
CNS: Neural tube (br) PNS: Neural crest cells
85
List the neuroendocrine derivatives of Neural Crest cells.
Adrenal medulla (chromaffin cells) (br) Enterochromaffin cells (br) Parafollicular C cells
86
List the non-neural structural derivatives of Neural Crest cells.
Pia/Arachnoid mater (br) Skull bones (br) Odontoblasts (br) Aorticopulmonary septum
87
Which neural-associated cells are sometimes referred to as the "fourth germ layer"?
Neural crest cells
88
Which embryologic structure induces the formation of the neural plate?
Notochord
89
What is the relationship between the neural plate and the neural tube?
Neural plate folds/seals → Neural tube (underneath ectoderm)
90
Contrast Vasculogenesis vs. Angiogenesis.
Vasculogenesis: De novo from blood islands (br) Angiogenesis: Sprouting from existing vessels
91
Which growth factor induces hemangioblast differentiation?
VEGF (Vascular Endothelial Growth Factor)
92
Identify the four primary sites of hematopoietic development.
1. Yolk sac blood islands (br) 2. AGM region (br) 3. Liver (br) 4. Bone marrow
93
By what time has the primitive heart been beating for almost five weeks?
By the time eight weeks have passed
94
What three sources combine to form the overarching musculoskeletal system?
1. Paraxial mesoderm (br) 2. Parietal layer of lateral plate mesoderm (br) 3. Neural crest cells
95
What specific tissue type undergoes condensation as the first required step for ANY bone formation?
Mesenchymal cells (loosely organized embryonic connective tissue)
96
Contrast Intramembranous vs. Endochondral ossification.
Intramembranous: Direct mesenchymal ossification (br) Endochondral: Cartilage model precursor
97
Which bones form via intramembranous ossification?
Cranial vault (calvaria) (br) Facial bones (most) (br) Clavicle
98
Which bones form via endochondral ossification?
Base of skull (br) Vertebrae (br) Ribs/Sternum (br) Limbs
99
How does the development of a synovial joint differ from fibrous/cartilaginous?
Requires central apoptosis to form the joint cavity
100
The neurocranium is divided into which two developmental parts?
1. Membranous (vault/calvaria) (br) 2. Cartilaginous (base/chondrocranium)
101
At what exact age does the posterior fontanelle generally close?
2 months of age
102
At what exact age does the mastoid (posterolateral) fontanelle generally close?
6 months of age
103
At what exact age does the anterior fontanelle generally close?
18 months of age
104
At what exact age do the cranial sutures generally close?
36 months of age
105
Which embryologic structures mainly form the viscerocranium (face skeleton)?
First two pharyngeal arches
106
Which specific bones are derived from the first pharyngeal arch?
Zygoma (br) Maxilla (br) Squamous part of temporal bone (br) Mandible
107
Which specific bones are derived from the second pharyngeal arch?
Malleus (br) Incus (br) Stapes
108
Which bones are the very first to become fully ossified, and when does it begin?
The ossicles (malleus, incus, stapes); begins in the fourth month of gestation
109
Identify the ossification centers of a developing vertebra.
3 Primary (1 body, 2 arch) (br) 5 Secondary (tips of processes/rims)
110
Describe the specific process of vertebral re-segmentation.
The caudal half of each sclerotome fuses with the cranial half of the adjacent sclerotome
111
What embryologic structure forms the ala (lateral mass) of the sacrum?
Costal processes of the first sacral vertebrae
112
What forms the annulus fibrosis of the intervertebral disc?
Circularly arranged fibers surrounding the nucleus pulposus
113
In what direction do the sternal bars fuse to form the sternum?
Cranial-to-caudal sequence
114
By what exact gestational week do the sternal bars fuse at the midline?
Tenth gestational week
115
What is the function of the Apical Ectodermal Ridge (AER) in limb development?
Induces underlying mesenchyme (Progress Zone) to remain undifferentiated/proliferate
116
What causes the formation of distinct digits from webbed hand/footplates?
Apoptosis in the interdigital spaces
117
When exactly do tactile pads develop to create patterns for fingerprints?
By the end of the eight-week
118
Exactly how far behind is lower limb development compared to upper limb development?
Approximately 1 to 2 days behind
119
Contrast the rotation of upper vs. lower limbs.
Upper: 90° Lateral (thumb lateral) (br) Lower: 90° Medial (big toe medial)
120
Define the term Myoblast.
Embryonic muscle cell (differentiated from myotome)
121
What specific cells form the epimysium and perimysium of skeletal muscle?
Fibroblasts
122
What specific structures form the endomysium of skeletal muscle?
External lamina and reticular fibers
123
What structure allows the diaphysis of a long bone to continue lengthening after birth?
Continued proliferation of chondrocytes in the epiphyseal growth plate
124
Contrast malformation vs. deformation in embryology.
Malformation: Intrinsic disruption (embryonic period) (br) Deformation: Extrinsic disruption (post-embryonic)
125
Define Agenesis in clinical embryology.
Absent organ due to absent primordial tissue (e.g., renal agenesis)
126
Define Hypoplasia in clinical embryology.
Incomplete organ development despite primordial tissue presence
127
Define Aplasia in clinical embryology.
Absent organ despite primordial tissue presence (e.g., DiGeorge syndrome)
128
What is a Craniopharyngioma?
Benign Rathke's pouch tumor (ectoderm) compressing optic chiasm
129
What does the acronym VACTERL represent?
Vertebral (br) Anal atresia (br) Cardiac (br) Tracheo-Esophageal (br) Renal (br) Limb
130
Contrast Cranioschisis vs. Craniosynostosis.
Cranioschisis: Vault failure (Anencephaly) (br) Craniosynostosis: Premature suture closure
131
Premature closure of the sagittal suture results in what specific skull shape?
Long and narrow skull (due to frontal/occipital expansions)
132
Premature closure of the coronal suture results in what specific skull shape?
Short skull
133
What is Klippel-Feil syndrome?
Fusion of cervical vertebrae → reduced mobility, short neck, low hairline
134
Contrast Spina bifida occulta vs. Spina bifida cystica.
Occulta: Intact cord covered by skin (minimal deficits) (br) Cystica: Meninges/neural tissue protrude through skin as a sac
135
What is the specific clinical danger of a cervical accessory rib?
May impinge on the brachial plexus or subclavian vessels (anesthesia of upper limbs)
136
Contrast Pectus excavatum vs. Pectus carinatum.
Excavatum: Concave depression of sternum (hollow chest) (br) Carinatum: Anterior projecting sternum (keel chest)
137
Contrast amelia vs. meromelia.
Amelia: Complete limb absence (br) Meromelia: Partial limb absence
138
Define Phocomelia.
Absence of long bones resulting in rudimentary hands/feet attached directly to trunk ("seal limb")
139
What specific bone absence characterizes a cleft hand or cleft foot?
Absence of the third phalangeal and metacarpal/metatarsal bones
140
Contrast Brachydactyly, Syndactyly, Polydactyly, and Ectrodactyly.
Brachydactyly: Short digits (br) Syndactyly: Fused digits (br) Polydactyly: Extra digits (br) Ectrodactyly: Absent digits
141
What is Poland Sequence?
Pectoralis minor/major absence + nipple displacement + digital defects
142
What is Prune belly syndrome?
Partial/complete absence of abdominal muscles → very thin wall, visible/palpable internal organs
Embryogenesis
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