3. Anatomy II p76-81
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- Fetal Circulation
- p. 76
- Do you want to see a high yiled diagram?
- Then go to page 76!
- Saturation level of blood in umbilical vein?
- 80%
- Foramen ovale: its function in fetal circulation?
- Most oxygenated blood reaching the heart via the IVC is diverted through the foramen ovale and pumped out the aorta to the head.
- Ductus Arteriosus: its function in fetal circulation?
- Deoxygenated blood from the SVC is expelled into the pulmonary artery and ductus arteriosus to the lower body of the fetus.
- What happens at birth, when infant takes a breath?
- Decreased resistance in pulmonary vasculature causes increased left atrial pressure vs right atrial pressure; foramen ovale closes; increase in O2 leads to decrease in prostaglandins, causing closure of ductus arteriosus.
- What drug can be given to close a patent ductus arteriosus?
- Indomethacin
- What drug can be given to keep a patent ductus arteriosus open?
- Prostaglandins
- Fetal-postnatal derivatives
- p.76
- Umbilical vein becomes the:
- ligamentum teres hepatis
- umbilical arteries become the:
- medial umbilical ligaments
- ductus Arteriosus becomes the:
- C2
- ductus venosus becomes the:
- ligamentum venosum
- foramen ovale becomes the:
- fossa ovalis
- allantois - urachus becomes the:
- median umbilical ligament
- notochord becomes the:
- nucleus pulposus
- urachal cyst or sinus is a remnant of the:
- allantois (urine drainage from the bladder)
- Aortic Arch Derivatives
- 1st arch:
- part of maxillary artery (1st is MAXimal)
- 2nd arch:
- stapedial artery and hyoid artery (Second = Stapedial)
- 3rd arch:
- common Carotid artery and proximal part of internal carotid artery (C is the 3rd letter of the alphabet)
- 4th arch:
- on left, aortic arch; on right, proximal part of right subclavian artery 4th arch (4 limbs) = systemic
- 6th arch:
- proximal part of pulmonary arteries and (on left only) ductus arteriosus. 6th arch = pulmonary and the pulmonary-to-systemic shunt (ductus arteriosus)
- diagram of aortic arch derivatives:
- see page 76!
- Branchial apparatus
- p. 77
- branchial clefts are dervied from:
- ectoderm
- branchial arched are derived from:
- mesoderm and neural crests
- branchial pouches are derived from:
- endoderm
- mnemonic to remember branchial apparatus derivation:
- CAP covers outside from inside (Clefts = ectoderm, Arches = mesoderm, Pouches = endoderm)
- Branchial arch 1 derivatives
- p. 77
- Meckel's cartilage:
- Mandible, Malleus,incus,sphenoMandibular ligament
- Muscles:
- muscles of facial expression, Stapedius,Stylohyoid, posterior belly of digastric.
- Nerve:
- CN IX
- Branchial Arch 2 derivatives
- p. 77
- Reichert's cartilage:
- Stapes, Styloid process, lesser horm of hyoid, Stylohyoid ligament
- Branchial arch 3 derivatives
- p.77
- Cartilage:
- greater horn of hyoid
- Muscle:
- stylopharyngeus (Think of pharnx: stylopharyngeus is innervated by glossopharyngeal nerve.
- Branchial arch 4 to 6 derivatives
- p.77
- Cartilages:
- thyroid, cricoid, arytenoids, cornicuate, cuneiform
- Muscles (4th arch):
- mostly pharyngeal constrictors, cricothyroid, levator veli palatini.
- 5th arch:
- makes no major developmental contributions
- Muscles (6th arch):
- all intrinsic muscles of larynx except cricothyroid
- Nerve (4th arch):
- CN X
- Nerve (6th arch):
- CNX (recurrent laryngeal branch)
- Branchial arch innervation
- p.77
- Arch 1 derviatives are supplied by:
- CN V2 and V3
- Arch 2 derivatives are supplied by:
- CN VII
- Arch 3 derivatives are supplied by:
- CN IX
- Arch 4 and 6 derivatives supplied by:
- CNX
- For diagram:
- see p. 81
- Branchial cleft derivatives
- p. 77
- 1st cleft develops into
- external auditory meatus
- 2nd through 4th clefts form:
- temporary cervical sinuses, which are obliterated by proliferation of 2nd arch mesenchyme.
- Persistent cervial sinus can lead to a:
- branchial cyst in the neck
- Ear development:
- p.77
- Bone: Incus/Malleus come from:
- 1st arch
- Bone: Stapes comes from:
- 2nd arch
- Muscle: Tensor tympani (V3) comes from:
- 1st arch
- Muscle: Stapedius (VII) comes from:
- 2nd arch
- External auditory meatus comes from:
- 1st cleft
- Eardrum, eustacian tube comes from:
- 1st pharyngeal membrane
- Branchial pouch derviatives:
- p. 78
- 1st pouch develops into:
- middle ear cavity, eustacian tube, mastiod air cells (1st pouch contributes to endoderm-lined structures of ear)
- 2nd pouch develops into:
- epithelial lining of palatine tonsil
- 3rd pouch (dorsal wings) develops into:
- inferior parathyroids (3rd pouch contributes to 3 structures: thymus, left and right inferior parathyroids)
- 3rd pouch (ventral wings) develops into:
- thymus
- 4th pouch develops into:
- superior parathyroids
- Aberrant development of 3rd and 4th pouches -->
- DiGeorge's syndrome --> leads to T-cell deficiency (thymic hypoplasia) and hypocalcemia (parathyroid glands)
- Thymus
- p. 78
- Site of:
- T-cell maturation
- Encapsulated or unencapsulated?
- encapsulated
- which branchial pouch?
- from epithelium of 3rd branchial pouches
- Lymphocyte origin?
- lymphocytes are of mesenchymal origin
- cortex is dense with:
- immature T cells
- medulla is pale with:
- mature T cells and epithelial reticular cells and contains Hassall's corpuscles. (think of the Thymus as "finishing school" for T cells. They arrive immature and "dense" in the cortex; they are mature in the medulla.
- What occurs at the corticomedullary junction?
- Positive and negative selection
- Thyroid Development
- p. 78
- Thyroid diverticulum arises from:
- floor of primitive pharnyx, descends into neck.
- Connected to tongue by
- thyroglossal duct, which normally disappears but may persist as a pyramidal lobe of thyroid.
- Formen cecum is:
- a normal remnant of the thyroglossal duct
- The most common ectopic thyroid tissue site is the:
- Tongue!
- Tongue development
- p. 78
- 1st branchial arch forms the
- anterior 2/3 of the tongue (thus sensation via CN V3, taste via CNVII)
- 3rd and 4th branchial arches form:
- posterior 1/3 of the tongue (thus sensation and taste mainly via CN IX, extreme posterior via CN X).
- Cranial nerves for taste?
- CN VII, IX, X (solitary nucleus)
- Motor innervation is via CN?
- CN XII
- Cleft lip and cleft palate:
- p. 78
- define cleft lip
- failure of fusion of the maxillary and medial nasal processes
- define cleft palate
- failure of fusion of the lateral palatine processes, the nasal septum, and/or the median palatine process.
- Diaphragm embryology
- p. 79
- diaphragm is derived from:
- Septum transversarium, Pleuroperitoneal folds, Body wall, Dorsal mesentery of esophagus (Several Parts Build Diaphragm. Diaphragm descends during develpoement but maintains innervation from above C3-C5. "C3, 4, 5 keeps the diaphragm alive."
- hiatial hernia
- abdominal contents may herniate into the throax due to incomplete development of the diaphragm.
- Bone Formation
- p. 79
- Intramembranous
- spontaneous bone formation without preexisting cartilage.
- Endochondral
- ossification of carilaginous molds. Long bones form by this type of ossification at 1o and 2o centers
- Meckel's Diverticulum
- p. 79
- definition
- persistence of the vitelline duct or yolk stalk. May contain ectopic acid-secreting gastric muscosa and/or pancreatic tissue.
- What is the most common congenital anomaly of the GI tract?
- Meckel's diverticulum
- Complications of Meckel's Diverticulum?
- can cause bleeding or obstruction near the terminal ileum.
- Comparison of Meckel's Diverticulum to Omphalomesenteric cyst?
- Cystic dilatation of the vitelline duct.
- Associated with
- urinary tract abnormalities and infertility
- Mnemonic to remember Meckel's diverticulum
- The five 2's: 2 inches long, 2 feet from the ileocecal valve, 2% of population, commonly presents in first 2 years of life, may have 2 epithelia.
- Pancreas and Spleen embryology
- p. 79
- Parcreas is derived from the
- foregut
- ventral pancreatic bud becomes the
- pancretic head, uncinate process (lower half of head), and main pancreatic duct.
- dorsal pancreatic bud becomes:
- everything else (body, tail, isthmus, and accessory pancreatic duct).
- Spleen arises from
- dorsal mesentery but is supplied by artery of foregut.
- Genital ducts
- p. 80
- Mesonephric (wolffian) duct
- Develops into Seminal vesicles, Epididymis, Ejaculatory duct, and Ductus deferens (SEED)
- Paramesonephric (mullerian) duct
- Develops into fallopian tube, uterus, and part of vagina.
- Mullerian inhibiting substance is secreted by:
- the testes to suppress development of paramesonephric ducts in males.
- Bicornuate uterus:
- p. 80
- results from
- incomplete fusion of the paramesonephric ducts.
- Male/female genital homologues:
- p. 80
- Genital tubercle (male) -->
- glans penis via dihydrotestosterone
- genital tubercle (female) -->
- glans clitoris via estrogen
- urogenital sinus (male) -->
- corpus spongiosum, bulbourethral glands (of Cowper), prostate gland: via dihydrotestosterone
- urogenital sinus (female) -->
- vestiubular bulbs, greater vestibular glands (of Bartholin), Urethral and paraurethral glands (of Skene): via estrogen
- urogenital folds (male) -->
- ventral shaft of penis (penile urethra) via dihydrotestosterone
- urogenital folds (female) -->
- labia minora via estrogen
- labioscrotal swelling (male) -->
- scrotum via dihydrotestosterone
- labioscrotal swelling (female) -->
- labia majora via estrogen
- Congenital penile abnormalities
- p. 81
- Hypospadia
- abnormal opening of the penile urethra on inferior (ventral) side of penis due to failure of urethral folds to close.
- Epispadia
- abnormal opening of the penile urethra on superior (dorsal) side of penis due to faulty positioning of the genital tubercle.
- epispadia is associated with
- exstrophy of the bladder
- Which is more common, hypospadia or epispadia?
- Hypospadial; fix hypospadias to prevent UTI's
- Sperm Development
- p. 81
- Spermatogenesis begins with
- spermatogonia (type A and type B; type A forms both type A and type B spermatogonia)
- full development takes how long?
- 2 months
- where does spermatogenesis occur?
- Spermatogenesis occurs in Seminiferous tubules.
- Derivation of sperm parts:
- p. 81
- acrosome is derived from
- the golgi apparatus and flagellum (tail) from one of the centrioles.
- what does the neck of the sperm have?
- Middle piece (neck) has Mitochondria.
- Sperm food supply is:
- fructose
- Meiosis and Ovulation:
- p. 81
- 1o oocytes begin and complete meiosis I when?
- begin: during fetal life; complete: just prior to ovulation. Meiosis I is arrested in prOphase for years until Ovulation.
- What phase is Meiosis II arrested in?
- Meiosis II is arrested in METaphase until fertilization. -- "An egg MET a sperm."