Basic Body Plan/Embryology Flashcards
What does the ectoderm form?
Central and peripheral nervous systems
Epidermis, hair, nails
Sensory epithelium of the nose, ear, and eye
What does the mesoderm form?
Skeletal, smooth and cardiac muscle
Cartilage, bone, connective tissue, blood
Kidneys and gonad
What does the endoderm form?
The epithelium of gut and its derivatives (liver, gallbladder, pancreas)
Epithelium of the respiratory
What is agenisis?
Missing organ caused by missing embryonic tissue (renal agenesis)
What is aplasia?
Missing organ due to growth failure of embryonic tissue (thymic aplasia)
What is hypoplasia?
Incomplete organ development (microcephaly)
What is a malformation?
Abnormal development of a structure (neural tube defects, cleft lip or palate, congenital heart defect)
What are the extrinsic errors of embryonic development?
Disruption and deformation
What is disruption?
External force leads to normal tissue growth arrest (amniotic band syndrome occurs when fibrous bands in amniotic cavity constrict growth of limbs or digits)
What is deformation?
External force leads to abnormal growth but not arrest, resulting in deformed or misshaped structures (potter sequence of syndrome is when the fetus is exposed to decreased amniotic fluid so the face and limbs are deformed because of lack of cushioning
What does exposure to teratogens during the first two weeks do?
Spontaneous abortion or no effect
What does exposure to teratogens during weeks 3-8 do to the baby?
This is when organogenesis occurs. It is a period of susceptibility, a period of maximum sensitivity to teratogens and when errors in morphogenesis are most likely to occur.
What effect do teratogens have 9 weeks until birth.
The organs are mature and the fetus rapidly grows. Exposure during this time disrupts growth and function.
What is a sequence?
A sequence is a primary anomaly itself resulting in additional defects
When is the embryo most susceptible to teratogen induced Limb malformations.
Weeks 4-5 because this is when limb patterning begins
What are reduction defects?
When part of (meromelia) or the entire limb (Amelia) is missing.
What are duplication defects?
This is when extra limb elements are present.
What is dysplasia?
This is malformation of part of the limb.
And example of this is abnormal fusion of the digits resulting from reduced apoptosis. Fingers do not separate into 5 regions
What occurs during the first week of embryogenesis?
Fertilization, cleavage, blastocyst formation and implantation
What are the Pluripotent stem cells and trophoblast cells of the embryo?
The pluripotent stem cells can give rise to any type of cell in the body, but not the placenta. The outer cells or trophoblast cells around the inner mass And blastocyst cavity;they form the fetal part of the placenta.
What happens by week two of embryogenesis?
The embryo blast and trophoblast each differentiate into two layers.
What happens at the end of week two in embryogenesis?
3 things
-The embryo has two layers: the epiblast and hypo blast.
-The trophoblast has two layers: the synctiotrophoblasts and cytotrophoblast
-two cavities form: the amniotic cavity and chorionic cavity
^the yolk sac is blastocyst cavity lined with hypoblast cells
What happens during week three of embryogenesis?
Establishment of the three germ layers that will give rise to all adult issues: the ectoderm, mesoderm and endoderm arise.
Describe the Epiblast Migration that gives rise to the endoderm mesoderm and ectoderm.
The epiblast cells First replace the hypoblast To form the endoderm (inside layer).
Epiblast Cell’s next migrate between the endoderm and the Epiblast to form the mesoderm.
The remaining cells that do not migrate become the ectoderm
What is folding? And when does it occur?
Holding resulting formation of the gut tube, the lateral and anterior body walls, information of the body cavity.
It occurs 17 to 22 days
When does the neural tube developer? How does the develop
It develops 17 to 22 days
It develops from a notochord. The notochord secretes factors important for tissue pattering Forming the neuroectoderm. This folds to form the neural tube.
The neural tube forms the central nervous system.
Cells on top of the neural tube are called the neural crest and they form the peripheral nervous system.
What is the notochord become?
The nucleus pulposis of intervertebral disks
What is caudle regression syndrome?
A disorder that impairs development of the lower half of the body
What is sirenomelia?
Fusion of two lower limbs at the midline.
What is sacrococcygeal teratoma?
A tumor that develops at the base of the coccyx.
What are the three body planes?
Proximal to distal: humorous develops 1st, then radius, and then wrist
Dorsal to ventral
Anterior posterior: interiors towards the head, posters away from the head (also called causal)
What is proximal to distal limb development dependent on?
The fibroblast growth factor gene.
Proliferating Ectoderm during forms of ridge called the apical ectodermal Ridge. This causes proliferation of the mesoderm.
How did digits form?
Digits form when apoptosis occurs in the Aer to separate into five separate ridges.
What is the most important signaling Protein Contributing to dorsal to venture a limb development?
Wnt-7a activates LMX-1 in mesoderm, causing it to form dorsal structures
What side of the limb (ventral or dorsal) does Wnt-7a make?
Wnt-7a contributes to the dorsal side of the limb.
Engrailed-1 makes the ventral side of the limb.
What gene contributes to anterior posterior limb development?
Sonic hedgehog gene.
What does the sonic hedgehog gene activate expression of?
transcription factors called homeobox jeans
What are the two types of bone development? And what do they give rise to?
The intramembranous or endochondral ossification
Intramembranous gives rise to bones of the skull and bones of the face.
The long bones form by endochondral ossification.
What is a dermatome?
An area of skin innervated by single spinal nerve and it’s dorsal root ganglion.
What is meromelia?
Part of the limb is missing
What is Amelia?
Entire limb is missing
What gene is produced at the limbs in the zone of polarizing activity?
Sonic hedgehog gene
What does the syncytiotrophoblast produce?
Human chorionic gonadotropin
During gastrulation, the N-word movement of cells from the app a blast occurs at this structure.
The primitive streak.
Where are the chondrocytes found in long bones?
The epiphysis
What is the region between the epiphysis and diaphysis where the bone grows in length called?
Epiphyseal (growth) plate or physis
From superior to inferior name the five zones in the epiphyseal plate?
the zone of resting cartilage, the zone of proliferating cartilage, the zone of hypertrophic cartilage, the zone of calcified cartilage, and the zone of ossification.
What is intramembranous ossification.
In the intramembranous ossification the mesenchyme is loosely organized, mainly Mesodermal tissue that develops into connective and skeletal tissues, including blood and lymph
The mesenchyme differentiates directly into osteoblast.
What is endochondral ossification?
The Mesenchyme differentiates into cartilage.
The cartilage becomes vascularized, bringing in osteoblasts and restricting proliferation chondrocytes to the ends of the bone.
What does mero mean?
Partial
What does Melia mean?
Limb
What does photo mean?
Sealed
What does brachy mean?
Short
What cavity does the Epiblast make? What type of cells make up the Epiblast?
The amniotic cavity, columnar cells
What type of cells make up the hypoblast cells? What cavity do they form?
They are made up of cuboidal cells and they make the yolk sac
What happens at the zone of calcified cartilage?
Chondrocytes mineralize the surrounding matrix.
What is the zone where chondrocytes toward the shaft side undergo hypertrophy and apoptosis
Zone of hypertrophic cartilage
What is this zone called where osteoblast bind the mineralize matrix and deposit bone matrix.
Zone of ossification
What did this somites differentiate into?
The axial skeleton, all skeletal muscle and some of the dermis of the skin.
