Embryo Final Flashcards
What is the dividing somite made up of
Mesodermal cells
What do mesodermal cells give rise to
Mesenchyme
What are the types of cartilage bone development
Inter-Cartilagenous or Endochondral ossification
What precedes Inter-Cartilagenous or Endochondral ossification
A temporary cartilage template of the same shape
What is special about the cartilage stage of bone growth
Bones can grow rapidly to match the growth of the fetus
How does intramembranous ossification happen
Condensation of mesenchyme becomes vascularized
At vascularization points what happens
Cells differentiate into Osteoblasts
When they begin to deposit osteoid tissue what do the vascularization points become
Ossification centers
How is bone matrix deposited
In the form of needles or spicules which become lamellae
These lamellae develop around blood vessels to form
Osteons
The spicules grow and thicken to become
Trabecullae
What are the two types of development for the skull
Neurocranium and Splanchnocranium
What does the neurocranium develop from
Mesenchyme surrounding the brain
What are the two types of neurocranium development
Neurochondrocranium and Neuromembranocranium
How does development of the Neurochondrocranium work
Cartilaginous base of the neurocranium and the skull and later endochondral ossification begins around 8 weeks
How does neuromembranocranium development work
Intramembranous ossification and forms the sides and the roof of the neurocranium
During fetal life, bones are separated by connective tissue membranes known as
Sutures
At the angle of bones large fibrous areas are formed.
What is the membrane covering these spaces called
Fontanelles
The anterior fontanelle is the largest and closes when
By the end of the second year
When do the posterior and anterolateral fontanelles form
2-3 months
When do the posterolateral fontanelles close
End of the first year
How many arches do humans have
- we start with 6, but the 5th disappears in 1.5 days
What is the first arch aka
Mandibular arch
What is the second arch aka
Reichert’s cartilage
What is the beginning of the vertebral column
The notochord
What does the notochord/vertebral column do
Gives axial support of vertebrates (chordates)
What is the nucleus pulposus
Modified tissue in the intervertebral disc
What does the vertebral column develop from, and what is the difference between the cranial and caudal portions
Forms from somite mesenchyme sclerotomes and the caudal portion is densely packed while the cranial is loosely packed
When do vertebral arches unite to form spinous processes
The third month after birth
If a disease or disorder is autosomal, what does that mean
Of the 22 chromosomes same in male and female
If a disease or disorder is sex-linked, what does that mean
Specific to male or female
What are chondrodystrophies
Abnormal development of cartilage or disproportionate growth patterns
Gene wise, how are most chondrodystrophies
Most autosomal dominant, some autosomal recessive and others are sex linked
What is Achondroplasia syndrome*not starred
Autosomal dominant. Slow cartilage growth and bone ossification. small stature and craniofacial megalocphaly. Lumbar lordosis and thoracolumbar kyphosis. mild hypotonia
What is Hypochondroplasia*not starred
Mild form of Achondroplasia. Small stature and short bowed lower limbs with lumbar lordosis
What is mucopolysaccaridosis
Storage of lipids and mucopolysaccharides in the the nervous system and mucopolysaccharides in the mesenchyme
What is Hulers
Mucopolysaccaridosis type 1. build up of glycosaminoglycans and deficiency of Alpha-L iduronidase which breaks down mucopolysaccharides
What is Cleidocranial Dysostosis
Clavivle agenesis. can lead to skull and jaw disorders
What is Occulta Spina Bifida
Limited to skeletal components and cannot see w/o and image taken
What is Cystica Spina Bifida
Meninges only (Meningocoele) or Meninges and Spinal cord (Meningomyelocoele)
What is Scoliosis
Abnormal Curvature of the spine
Where is the notochord supposed to be retained
In the disc nucleus pulposus
What is a Chordoma
When the notochord is retained in vertebral bodies, leading to slow growing tumors
What is Cranial Dysostosis
Lack of ossification of the skull at the time of birth
What is Craniostenosis
Premature closure of the sutures of the skull. Leads to brain and eye deformities
What is Oxycephaly
All sutures close prematurely, but it is symmetrical closure
What is Trigonocephaly
Premature fusion of the two frontal bones metatopic suture located in the forehead. (look like the cone heads)
What is Plagiocephaly
When the sutures close asymmetrically
What is Scaphocephaly
When the sagittal sutures close prematurely
What is Acrocephaly (brachycephaly)
When the Coronal sutures are involved
What is Aperts
Aperts is the combination of Acrocephaly and Syndactyly
What is Syndactyly
Fusion of the digits
What is Crouson’s
Scaphocephly with NO syndactyly
What is considered normal for skull size and brain weight
Skull-56 cm and brain weight 1300 grams
What is significant about Thalidomide babies
The were born with Amelia or Meromelia
What is Amelia
Complete absence of limb(s) can be caused by environmental factors
What is Phocomelia
Absence or reduction of the proximal part of the limb(s) can be caused by environmental factors
What is Meromelia
Absence or reduction of the distal part of the limb(s) can be caused by environmental factors
What is Sympodia
Hypoplasia and fusion of the lower limbs. Etiology-Spontaneous
What is Dichiria
Duplication of the distal parts of limbs. Etiology-Autosomal dominant
What is Polydactyly
Presence of extra digits. Etiology-Autosomal dominant
What is Syndactyly
Fusion of the digits. Etiology-Autosomal Dominant
What is Brachydactyly
Shortness of the digits. Etiology-Autosomal Dominant
What is Hyperphalangism or polyphalangism
Long digits with extra phalanges. Etiology-Autosomal Dominant
What do somites divide into
Dermamyotomes and Sclerotomes
What do Dermamyotomes divide into
Dermatomes for the skin and myotomes for the muscles
What do sclerotomes divide into
Skeleton
What is myogenesis
Muscle formation
What are portion of the somite are muscles developed from
The Myotome
What layer does the muscular system develop from
The mesoderm layer
What does the iris of the eye develop from
The neuroextoderm
What are the divisions of skeletal muscles
Epimere and hypomere
What is the small dorsal division called
Epimere or epiaxial
What is the large vental division called
Hypomere or hypaxial
What do epimeres form
The extensor muscles of the vertebral column and Dorsal primary rami
What do hypomeres form
Give rise to the muscles of the limbs and body wall and Ventral primary rami
What is the innervation of the first Branchial arch
Trigeminal Nerve (CN V)
What is the innervation of the second Branchial arch
Facial Nerve (CN VII)
What is the innervation of the third Branchial arch
Glossopharyngeal (CN IX)
What is the innervation of the fourth and sixth Branchial arches
Vagus (X) and Hypoglossal (XII)
What are limb buds made from
Muscular Mesenchyme
The mesenchyme develops into what groups
Extensors (dorsal group) and Flexors (ventral group)
Where does smooth m. derive from
Splanchnic mesoderm
Where does smooth m. of the iris derive from
Neuroectoderm
Where does cardiac m. derive from
Splanchnic mesoderm
T/F: Most muscle defects are bilateral
False, most are unilateral
What is the order of muscle defects frequency
Pectoralis, Trap and SCM, Deltoid and infraspinatus (rare), and Palmaris longus (~13%)
T/F: Abdominal defects are NEVER bilateral
False, They are ALWAYS bilateral
What is Prune belly
Distended abdomen from aplasia of the abdominal musculature
Order of frequency of bilateral absence of abdominal muscles
Transverse abdominus, Rectus abdominus (below umbilicus), Internal and external oblique and rectus abdominis (above umbilicus)
What is Torticollis
SCM is injured during development based on its position in the uterus and m. development. Different than injury during birth process
Where does the urinary and genital systems extend
They extend along the paraxial mesoderm from the 7th to 28th somite level
What gives rise to the urinary system
Neurogenic cord
What gives rise to the genital system
Genital ridge
What are the 3 types of of kidneys
Pronephroi, Mesonephroi and Metanephroi
Where are all three kidneys seen in humans
Human development starting out in the 3rd week
What is the pronephroi kidney
Rudimentary and has very little function 7th-10th somite level (degenerates around 4th week)
What is the Mesonephroi kidney
Well developed and function briefly located at the 10-26th somite levels
What are the differences in mesonephric tubules in Males vs. Females
In males some are retained and form the genital duct system. In females, none are retained
What are the Metanephroi kidneys
Permanent kidneys located lateral to the mesonephric duct 26-28th somite. (5th week)
What develops from the flat end of bud of metanephroi
Renal Pelvis
What develops from the renal pelvis
Major or minor calyces
Branching of the minor calyces produce what
Collecting duct system of the kidneys
What is the mesodermal mass that divides the cloacal
Cloacal Septum
What is the Allantois continuous with
The Allantois and bladder are continuous. Eventually the allantois becomes vestigial
What is the Allantois in the fetus
Urachus
What is the Allantois called in the adult
Median umbilical ligament
What is renal agenesis
Can be bi or unilateral. When the kidneys do not form
What is renal hypoplasia
Incomplete development of the kidneys. Can be bi or unilateral
When it comes to living, both bilateral renal hypoplasia and agenesis are…
Compatible with uterine life, but not with postnatal life
What kind of kidneys are compatible with life
Unilateral Renal agenesis and Unilateral renal hypoplasia
Congenital cystic kidney Type 1
Type 1 found in infants, early death unless dialysis or kidney transplants. Giant/Sponge kidneys. symmetrical
Congenital Cystic Kidney Type 2
Variable in size and shape, Unilateral, and cysts grow larger with age
Congenital Cystic Kidney Type 3
Normal and abnormal tissue. bilateral. small cysts at birth that grow. Found in trisomy 13-15, 18,21,22
Congenital Cystic Kidney Type 4
Urethral obstruction. Cysts found in collecting tubules. If severe fetal/neonate death. If mild then surgical repair
Congenital Cystic Kidney Type 5
Could see in clinic. Present before birth, but doesn’t manifest till adult. Onset 40s if not tx death in 50s. Low back pain from kidney infections
When the kidneys are fused at both ends, what is it called
Donut kidney
What is the tissue connecting two kidneys that form a horseshoe kidney called
Isthmus
What is the problem with a horseshoe kidney, and what conditions is it seen in
Horseshoe kidney usually cannot ascend to the lower lumbar area. Trisomies 13-15, 18, 21, and Turner’s
What are Wilm’s Tumors
Renal tumors in children, rapid growth and metastases. Mesodermal origins. Symptoms are Facial features, vision, urinary, and ambulation probs
When does the reproductive system start developing
5-6th week
When is sex identification possible
8th week, but is still hard to do
What stage can the sex of embryo NOT be determined
Indifferent stage
What are the areas of development of Gonads
Coelomic epithelium, Inner mesenchyme tissue, primordial germ cells, and reproductive system
Where does the genital ridge form
A bulge into the coleum
What makes up the genital ridge
A mesenchyme inner mass covered by coelum epithelium
The genital ridge arrange themselves into what
Primary sex cords
The indifferent Gonad has what 2 parts
Cortex and Medulla
Cortex in Males vs. Females
Males cortex regresses and females cortex develops
Medulla in Males vs. Females
Males medulla develops and females medulla regresses
In testes cords epithelial cells develop into what
Sertoli cells
Primordial germ cells develop into
Spermatoblasts
T/F: Testes cords remain solid until puberty
True
Mesonophric ducts (kidneys) play an important role in what
The male reproductive system
Mesonephric ducts form what 4 structures
Epididymis, ductus deferens, ejaculatory duct, and cranial part-efferent ducts
Paramesonephric ducts develop on each side of the body in females to form what
The caudal ends fuse to form Y shape creating the uterus and vagina
T/F: The genitalia pass through an indifferent stage
True
Are accessory sex glands found in females
No.
What are the accessory sex glands in males
Seminal vesicles, prostate, and bulbourethral glands
What is Ovarian Hypoplasia and is aka
Turner’s Syndrome. Ovaries are small in size, poor breast development, small uterus, and only some ovarian function. can be uni or bi lateral
Can somebody with Unilateral ovarian hypoplasia (Turner’s Syndrome) still give birth to a normal infant
Yes
What is pure gonadal dysgenesis
Germ cells do not migrate from the yolk sack, but still have a normal karyotype 46, XX or XY
Chromatin Positive vs Negative
Positive normal female (Barr bodies) and Negative normal male
What is androgen insensitivity aka Testicular Feminization Syndrome
Appears as normal female despite presence of testes. Chromatin negative genetic male: 46,XY. Not noticed in childhood
What is Adrenogenital syndrome
Excessive androgen production from the adrenals.
Genetic females 46XX. Masculinization result of high levels of androgens-adrenal cortex. chromatin positive
True Hermaphroditism is aka
Complete androgen insensitive syndrome. When both ovaries and testes tissues are present. Very rare
What is Mosaicism
Mix of cells with different karyotypes. Normal karyotype and trisomy 21 46, XX and 47, (21) XXY
What is Hypospadias
Urethral opening on the ventral (under) side of the penis instead of the tip
What is Epispadias
Urethral opening on the dorsal (top) side of the penis
When is the cardiovascular system developed
End of the 3rd week
Why is growth of the fetus so rapid
For nutrition requirements
What are angioblasts
Stem cells that give rise to blood vessels
What is angiogenesis
Development of new blood vessels
Where do cells that form blood vessels come from
Blood Islands
What arises from the 1st pair of longitudinal vessels
Dorsal Aorta
What forms anteriorly from the longitudinal vessels
Aortic Arches
What forms posteriorly from the longitudinal vessels
Heart Primordia
What arises from the second set of longitudinal vessels
Vitelline and umbilical veins
Function of vitelline veins
Returns blood from the yolk sac
Function of umbilical veins
Brings blood from chorion (placenta)
Function of cardinal veins
Returns blood from body
Process of the development of the heart
Two thin walled enothelial tubes, continuation of the first aortic arches that eventually fuse to form a single tube from heart tubes
What 2 structures of the heart grow faster than the rest
The bulbus and ventricle, giving the heart an S shape
How does formation of the atrium take place
Atrium starts at the lower end, and the growth end is in the upper portion
What two types of tissue formation take place to achieve the chambers
Tissue growth and overgrowth
How does tissue formation of the heart work
Fuse together to make two chambers aka the septum
How does overgrowth tissue formation of the heart work
In the developing ventricle, Tissue grows on either side of the narrow strip and the walls expand and form the septum
What is the septum Primum
Sick shaped crest, roof of atrium
What is the ostium primum
Opening between septum primum and endocardial cushion
What is the ostium secundum
Opening in the septum primum
What is the septum secundum
Right atrium incorporates part of the sinus a new septum appears
What is the oval foramen
Opening in the septum secundum
When do the septum primum and septum secundum fuse and the oval foramen close
After birth
What happens if the septum primum and secundum fail to fuse
In 25% they do not fuse and Probe Patency of the Oval Foramen occurs
The simple ebb and flow type of circulation the heart experiences begins on the 22 day and originates from what kind of muscle
Myogenic Muscle
What happens to heart circulation by the end of 28-30 days
The heart has a unidirectional blood flow with contractions of the heart tube
How does oxygenated blood enter the fetus from placenta
Via veins
How does deoxygenated blood leave the fetal body
Via arteries
What are ductus arteriosus
Shunts in the fetal pulmonary trunk that diverts blood back to the aorta. *Bypasses the lungs
What are ductus venosus
Shunt in fetal heart that causes the oxygenated blood to bypass the fetus’ developing liver to reach the vena cava
What do the septum of the truncus and bulbus fuse to form
The spiral septum-Aorticopulmonary Septum
What do the Cavum Aorticum and the Cavum Pulmonare separate
The Ascending aorta and pulmonary trunk
What is Acardia
Absence of the heart
What is ectopic cordis
Heart is located through the sternal fissure. Limited life expectancy w/o surgery
What is Dextra Cardia
The heart is located in the right hemithorax. Usually associated with other anomalies such as situs inversus (organs flipped)
What is an Atrial Septal Defect
Small patent foramen ovale to complete absence of the interatrial septum. loud systolic murmur. may require surgery
What is a Ventricular Septal Defect
Uncomplicated VSD is considered harmless. Harsh systolic murmur at Erb’s point. Can spontaneous closure
Where is Erb’s point
In the 3 and 4 intercostal space near the sternal border
What is the Tetralogy of Fallot
Pulmonary stenosis, VSD, Overriding aorta, and right ventricular hypertrophy
What is the life expectancy of Tetralogy Fallot and symptoms
12 years w/o surgery. Cyanosis and paroxysmal dsypnea with exertion
What is the Triology of Fallot
Pulmonary stenosis, ASD, and right ventricular hypertrophy
Where does the nervous system originate from
The Ectoderm
What happens to the position of the spinal cord during the third month of development
Cord extends entire length of embryo
What happens to the position of the spinal cord during the sixth month of development
End of spinal cord level of 1st sacral vertebra
What happens to the position of the spinal cord at birth of development
Level of the 2nd and 3rd lumbar vertebra
What happens to the position of the spinal cord during adulthood of development
Lower end of the first lumbar vertebra
What are the primary brain vesicles
Forebrain (Prosencephalon), Midbrain (Mesencephalon), and Hindbrain (Rhombencephalon)
What does the Forebrain divide into
Telencephalon and Diencephalon
What does the Hindbrain divide into
Metencephalon (leads to Pons, Cerebellum, and Myelencephalon/Medulla
What are the flexures of the brain
Cephalic, Cervical and Pontine flexures
Where is the Cephalic Flexure
Midbrain and bends ventrally
Where is the pontine flexure
Metencephalon and Myelencephalon
What are Category A drugs
Drugs for which studies have not shown a risk to the fetus
What are Category B drugs
Drugs with no human studies, but animal studies have shown an effect on the fetus
What are Category C drugs
Drug studies are inadequate in both humans and animals to shown an effect on fetus
What are Category D drugs
Drugs can definitely cause harm to fetus, but benefits mother
What are Category X drugs
Drugs cause harm to fetus with no benefit to mother
What is a Teratogen
Any agent that can produce a congenital malformation
What is Teratology
The study of abnormal development
What is a Sign
Objective evidence of a disease. SEE SIGNS
What is a Symptom
Subjective evidence of a disease. They tell you
What is a Syndrome
Collection of Signs and Symptoms that occur together
What is etiology
Study of the cause of disease
When do the nervous systems develop
3-7 weeks
When does the cardiac system develop
4-6 weeks
When do the ears and eyes develop
4-8 weeks
When do the limbs develop
4-7 weeks
What is nondisjunction
When the chromosomes fail to divide properly leading to an abnormal karyotype
Karyotype of Trisomy 21
47 (21)XX or XY
T/F: Klinefelter’s can be either XXY or XYY
True
S/S of Klinefelter’s
Taller than average, Reduced facial hair, Normal IQ, gynaecomastia, feminine fat distribution, testicular atrophy or cryptorchism (undescended testes)
T/F: Klinefelter’s and Turner’s syndrome are both chromatin negative
True
What is Monosomy of sex chromosomes known as
Turner’s Syndrome
What are some possible characteristics of Turner’s syndrome
Horseshoe kidney, Unilateral renal agenesis, lack of breast development and infantile external genitalia
What are the mechanisms of damage in the body
Produced free radicals which break chemical bonds. This causes new chemical bonds and cross-linkage between macromolecules. Also cause damage to DNA, RNA, and Proteins that regulate vital cell processes
When is is the fetus most sensitive
First trimester. can result in death
What are the risks in the second trimester
Major organs most sensitive, malformations
What can happen in the 3rd trimester of pregnancy posing a risk to the fetus
Cell population can become depleted leading to leukemia
