Genetics Block I Flashcards
What are the two types of bone developmental processes?
- Intramembranous ossification - via mesenchyme w/ pre-existing membrane
- Intracartilagenous ossification via mesenchyme forming a cartilaginous model
Which type of bone developmental processes do long bones undergo?
Intracartilagenous ossification
Which type of bone developmental processes does flat bones of skull, mandible, and clavicle undergo?
Intramembranous ossification
Skeleton of the face is derived from the neurocranium or viscerocranium?
Viscerocranium
The protective case around the brain is derived from the neurocranium or viscerocranium?
Neurocranium
The roof of the neurocranium is formed by which type of bone ossification? (intramembranous or intracartilagenous)
Made up of flat bones = Intramembranous
The base of the neurocranium (sphenoid, ethmoid, petrous, mastoid, and basilar part of occipital bone) is formed by which type of bone ossification?
Intracartilagenous/endochondral ossification
The membranous neurocranium (roof/vault) is derived from which embryological structure? (2)
- Neural crest cells
2. Paraxial mesoderm
Prechordal chondrocranium consists of the ethmoid and sphenoid bone, where do these structures arise from?
Neural crest cells
Chordal chondrocranium consists of structures that are posterior to the pituitary fossa (petrous bone, base of occipital bone, etc.), where do these structures arise from?
Paraxial mesoderm
The viscerocranium is derived from which embryological structure?
Neural crest cells
Viscerocranium formed mainly via 1st & 2nd pharyngeal arches
Craniosynostosis
Premature closure of sutures
Scaphocephaly - premature of sagittal
Brachycephaly - coronal
Plagiocephaly - coronal closure on one side only
Achondroplasia primarily affects long bones, what type of bone ossification do they undergo?
This is the same for ALL types of skeletal dysplasia (Thanatoporic dysplasia, Hypochondroplasia, Cleidocranial dystosis)
Intracartilagenous ossification
Cause of hemivertebra
Mesenchymal cells from one sclerotome fail to migrate
Absence of 1/2 of vertebra = scoliosis
Origin of vertebral arches? Vertebral column and ribs?
Sclerotome via paraxial mesoderm
Spondylolysis and spondylolisthesis are development processes associated with vertebral arches and the vertebral bodies, where are these derived from?
Sclerotome via paraxial mesoderm
Bony portion of ribs are derived from where?
Sclerotome of the paraxial mesoderm
Costal cartilages of the ribs are derived from where?
Sclerotome cells that migrate across the lateral somatic frontier into the lateral plate mesoderm
Derivation of the sternum?
Parietal layer of the lateral plate mesoderm of the paraxial mesoderm
Pectus excavatum is when the sternum is sunken posteriorly, where is the sternum derived from?
Parietal layer of the lateral plate mesoderm of the paraxial mesoderm
Which mesoderm layer is skeletal muscle derived from
Paraxial mesoderm
Which mesoderm layer is smooth muscle derived from
Splanchnic mesoderm surrounding the gut tube
Which mesodermal layer is cardiac muscle derived from
Splanchnic mesoderm surrounding the heart tube
Somitomeres 1,2,3,5 of the mesoderm give rise to what structures?
Muscles of the eyeball
Somitomere 4 Somitomere 6 Somitomere 7 Somites 1,2 Somites 2-5
4 - muscles of mastication 6 - muscles of facial expression 7 - stylopharyngeus 1,2 - intrinsic laryngeals 2-5 - tongue
Extensor muscles of the vertebral column are derived from which layer of the myotome?
Epimere of the myotome
Anterolateral muscles of the body wall and limbs are derived from which layer of the myotome?
Hypomere of the myotome
Poland syndrome is an absence of the pectoral is minor and partial loss of pectoral is major, what are these muscles origins?
Skeletal muscle = Paraxial mesoderm of the myotome
Each limb bud contains 3 components, what are they? (ZAS)
Z - Zeugopod –> radius/ulna, tibia/fibula
A - Autopod –> carpals, metacarpals, digits/tarsals, digits/metatarsals
S - Stylopod –> humerus and femur
Of the limb mesenchyme, where is the musculature derived from?
Hypomere part of the somite
Of the limb mesenchyme, where is the skeleton, blood vessels, and CT derived from?
Parietal layer of lateral plate mesoderm
What type of bone ossification occurs for the clavicle?
Intramembranous ossification
The skeleton of the upper and lower limbs develop via what bone ossification?
Intracartilagenous ossification via lateral plate mesoderm
The earliest arterial supply of the upper limb bud is the ____ and ____
Axis artery and terminal plexus
The axis artery gives rise to which upper limb arteries?
First to branch = posterior interosseous, median artery
Last to branch = radial and ulnar arteries
Axis artery persist as the axillary, brachial, anterior interosseous, and deep palmar arch arteries
Which UL arteries persist from the axis artery? (4) DAAB on em
Radial artery anastomoses with terminal plexus forming:
- Deep palmar arch
- Axillary
- Anterior interosseus
- Brachial
For LL vasculature, what arteries persist from axis artery? (4) DIPS
- Distal part of peroneal a.
- Inferior gluteal artery
- Proximal part of popliteal
- Sciatic artery
Where does the femoral a. arise from in LL vasculature?
External iliac; femoral a. gives rise to profound femoris a.
What initially branches from the axis artery in the LL vasculature?
Anterior and posterior tibial a.
What are the 3 derivatives of the dermis?
- Neural crest cells - dermis in face and neck
- Paraxial mesoderm - dermis in the back
- Lateral plate mesoderm - dermis for limbs and body wall
Hair is derived from where?
Ectoderm
Origin of mammary glands?
Epidermis of the ectoderm
Derivation of the epithelial lining and glands of mucosa of the GI tract?
Endoderm; while the remaining is via visceral/splanchnic part of lateral plate mesoderm
What are the three divisions of the primitive gut tube?
- Foregut
- Midgut
- Hindgut
The ventral mesentery is divided into two parts by the ____ which are ___ and ____
Liver
- Lesser omentum –> extends from lower esophagus, stomach and upper duodenum to liver
- Falciform ligament –> to ventral body wall
Foregut derivatives? (6)
- Esophagus
- Gall bladder
- Liver
- Pancreas
- Stomach
- Upper duodenum
In what rotation does the stomach move?
90 degrees clockwise along the longitudinal axis
Liver buds appear as an outgrowth of _______ epithelium at distal end of ______. This also gives rise to what?
endodermal; foregut
Parenchyma of liver and bile capillaries
Where does the pancreas develop from?
Endoderm of the foregut tube (duodenum) (both endocrine and exocrine)
What are the two pancreatic buds, what do they consist of and where are they located?
- Dorsal - upper part of head, neck, body, tail - dorsal mesentery
- Ventral - uncinate process, lower part of head - ventral mesentery close to bile duct
The main pancreatic duct of Wirsung is derived from which pancreatic structure?
Distal part of dorsal pancreatic duct and the entire ventral pancreatic duct
The accessory pancreatic duct of Santorini is derived from which pancreatic structures?
Proximal part of dorsal pancreatic duct
Midgut derivatives
- Lower duodenum
- Jejunum, ileum
- Cecum
- Vermiform appendix
- Ascending color
- Proximal 2/3 transverse colon
The primary intestinal loop is divided into what two parts containing what organs?
- Cephalic/Cranial limb - distal duodenum, jejunum, & upper part of ileum
- Caudal limb - lower ileum, cecum, appendix, ascending and proximal 2/3 transverse colon
Which organ of the midgut is the first to retract into the abdominal cavity?
Jejunum
During intestinal looping, which organs lose their mesenteries (pressed against peritoneum of posterior ab wall)? (retroperitoneal)
- Ascending and descending colon
- duodenum
- pancreas
During intestinal looping, which organs retain their free mesenteries?
- Appendix
2. Sigmoid colon
Hindgut derivatives (6)
- Distal 3rd t. colon
- Descending colon
- Sigmoid colon
- Rectum
- Upper anal canal
- Internal lining of urinary bladder and urethra
Derivative of superior 2/3 and inferior 1/3 of anal canal?
- Superior - endodermal cloaca
2. Inferior - ectodermal pit
Abnormal process in megacolon (Hirschsprung’s disease)?
Abnormal migration of neural crest cells
From which mesodermal origin does the urogenital system arise from?
Intermediate mesoderm
Which part of the kidney forms the permanent kidney?
Pronephros
Mesonephros
Metanephros
Metanephros
Mesonephros functions for a brief period
What structure persists in males to form efferent ductules of testis?
Mesonephric/Wolffian tubules/duct which open into urogenital sinus (cloaca)
-degenerates in females
The ureteric bud comes from what kidney structure?
Lower end of mesonephric duct which eventually forms the primitive renal pelvis
Describe the formation of the renal pyramids
Renal pelvis via uteric bud (mesonephric duct) splits into 2-3 major calyces
Which divide and form minor calyces and collecting tubules which converge on minor calyx forming renal pyramid
List the 4 derivatives of the ureteric bud
Via mesonephros
- Ureter
- Renal pelvis
- Major and minor calyces
- Collecting tubules
List the 4 derivatives of the metanephros
- DCT
- PCT
- LOH
- Bowman’s capsule
Renal agenesis occurs in oligohydramnios, what structure fails to develop?
Ureteric bud via mesonephros
Renal hypoplasia includes small amounts of renal parenchyma which are derived from which kidney part?
Metanephros
Polycystic kidney disease contains cysts that are thought to be caused by:
Failure of union b/w developing convoluted tubules and collecting tubules which arise from the metanephros
Horseshoe kidney occurs by fusion of lower poles preventing what process?
Ascent into the abdominal cavity is prevented due to the root of the inferior mesenteric artery where the inferior poles are attached across
What are the 3 parts of the urogenital sinus and what do they give rise to?
- Vesical - urinary bladder (continuous with allantois)
- Pelvic - prostate, bulbourethral glands & membranous urethra, entire female urethra (paraurethral, urethral glands, vestibular glands)
- Phallic (definitive urogenital sinus) - penile urethra and vestibule in females
Mucosa of the trigone is derived from mesoderm and initially lined with mesoderm, but eventually gets replaced with ______
Endodermal epithelium
Where is the muscle and CT of the urinary bladder derived from?
Splanchnic part of lateral plate mesoderm
Once the allantois detaches from the bladder, what does it turn into?
Urachus = median umbilical ligament
Where is the epithelium of the urethra derived from?
Urogenital sinus - endoderm
Female urethra is derived from which germ layer?
Endoderm
Exstrophy of the cloaca is caused by a defect of the ____ body wall and occurs from what abnormal function?
Ventral; mesodermal fail to migrate in lower part of abdomen and in perineum (around cloaca)
Origin of the cortex of the suprarenal glands
Mesoderm
Origin of the medulla of the suprarenal glands
Neural crest cells; eventually get surrounded by the fetal and permanent cortex
Once neural crest cells migrate to form suprarenal glands, what do they differentiate into?
Chromaffin cells
Sertoli cells originate from?
Mesoderm of seminiferous cords
Spermatogonia originate from?
Primordial germ cells - epiblast
Leydig cells originate from?
Mesoderm b/w seminiferous cords
Follicular cells originate from?
Secondary sex cords; cortical sex cords
Oogonia original from?
Primordial germ cells
During the dev of paramesonephric/mullerian ducts, the paramesonephric duct crosses mesonephric duct caudally from ventral side, unites at midline forming ______
Uterovaginal primordium which opens into posterior wall of urogenital sinus
When the testis secretes Mullerian inhibiting substance (Sertoli cells) what is suppressed?
Paramesonephric ducts
What does testosterone (Leydig cells) induce in male genital development?
Mesonephric ducts stimulated
Epididymis, vas deferens, seminal vesicles, external genitalia, penis, scrotum, prostate
What are the 2 remnants of the mesonephric ducts in the male?
- Epididymis
2. Vas deferens
What are the 2 remnants of the paramesonephric ducts in the male?
- Appendix testis
2. Prostatic utricle
Remnant of mesonephric tubules in females
Epoophoron and paroophoron (cranial and caudal tubules) in mesovarium
Remnant of mesonephric DUCT in females
Gartner’s cyst; a small caudal portion that persist in the wall of uterus or vagina
What germ layer covers the tip of the phallus?
Ectoderm; which forms into a solid epithelial cord and forms the external urethral meatus (glandular part of urethra)