Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
93 Cards in this Set
- Front
- Back
Paraxial Mesoderm
|
thick plate of mesoderm on each side of the midline organized in craiocaudal sequence into segments known as somitomeres
|
|
Somititomeres 1-7 develop into?
|
don't develop into somites, but contribute to mesoderm in head and neck, pharyngeal arches
|
|
Somitomeres 8+ develop into?
|
further condense into craniocaudal sequence to form 42-44 pairs of somites in trunk region, and have final count of ~35 pairs after caudal-most disappear
|
|
Somites differentiate into?
|
differentiate into:
--sclerotome: cartilage and bone component --myotome: muscle component --dermatome: dermis of skin |
|
Head and neck musculature derived from?
|
somitomeres 1-7 of head and neck region, to form pharyngeal arches
|
|
Extraocular muscles
|
derived from somitomeres 1,2,3 &5; 1-3 are preotic myotomes/somites; innervated by CN III, IV and VI
|
|
Tongue muscles
|
derived from myotomes in occipital region & innervated by CN XII
|
|
Trunk Musculature derived from and partition into?
|
derived from myotomes in trunk region; partition into dorsal epimeres and ventral hypomeres
|
|
Dorsal Epimeres
|
develop into intrinsic back muscles & innervated by dorsal rami of spinal nerves
|
|
Ventral Hypomeres
|
develop into prevertebral intercostal and abdominal muscles; innervated by ventral rami of spinal nerves
|
|
Limb musculature dervied from and differentiates into?
|
myotomes/somites in upper limb bud and lower limb bud regions; mesoderm migrates to form posterior and anterior condensations
|
|
Posterior Condensation
|
1) devos into extensor & suppinator muscles of upper limb
2) devos into extensor and abductor muscles of lower limb |
|
Anterior Condensation
|
1) devos into flexor and pronator muscles of upper limb
2) devos into flexor and adductor muscles of lower limb |
|
Smooth Muscles iof GI and Tunica Media of blood vessels
|
derived from mesoderm
|
|
Cardiac Muscle
|
derived from mesoderm surrounding primitive heart tube & becomes myocardium
|
|
Septum transversum devos from?
|
Cerivcal somites (myotomes; innervated by phrenic nerve
|
|
Abdominal muscles devos from?
|
Hypomere (ventral part of myotome)
|
|
Extrinsic eye muscles devos from?
|
Preoctic somites (myotomes) found near prochordal plate; specifically, somitomeres 1-3
|
|
tongue muscles devos from?
|
Intrinsic and Extrinsic arise from occipital somites (myotomes)
|
|
Erector spinae devos from?
|
Epimere, from dorsal part of myotome
|
|
Upper Limb devo begins with?
|
activation of a group of mesodermal cells of the lateral plate of mesoderm
|
|
Lateral plate mesoderm migrates into limb bud and?
|
condenses along central axis, forming vasculature & skeltal components of upper limb
|
|
Mesoderm from somites migrates to upper limb and?
|
condenses to form musculature components of upper limb
|
|
Hox 3.3?
|
is expressed by future limb mesodermal cells prior to limb bud formation
|
|
AER?
|
Place at tip of limb bud where limb mesoderm is signaled to thicken; interacts with underlying mesoderm to promote outgrowth of limb bud by promoting mitosis & preventing terminal differntiation of mesodermal cells at tip of limb bud
|
|
Zone of polarizing activity (ZPA)
|
mesodermal cells at base of limb bud that direct organization of limb bud & patterning of digits, which involves retinoic acid & Hox-4
|
|
Digit formation
|
occurs as result of selected apoptosis within AER such that 5 separate regions of AER remain at tips of future digits
|
|
Neurocranium devos from?
|
neural crest cells except for basilar part of occipital bone region
|
|
Basilar part of occipital bone devos from?
|
Mesoderm cells of occipital sclerotomes
|
|
Viserocranium
|
bones of face involving pharyngeal arches , devos from neural crest cells except for laryngeal cartilages
|
|
Laryngeal cartilages devo from?
|
mesoderm within pharyngeal arches 4 & 6
|
|
Sutures: define
|
Dense connective tissue that separate flat bones of skull during fetal and infant life
|
|
Sutures: List
|
5: frontal, sagittal, lamboid, coronal & squamosal
|
|
Sutures allow for?
|
flat bones of skull to deform during childbirth ("molding") and expansion and growth of brain during infancy
|
|
Define fontanelles
|
Large fibrous areas where several sutures meet, a total of six
|
|
Anterior Fontanelle
|
Largest and readily palpable in infant; pulsates due to cerebral arteries; can be used for blood sample from superior sagittal sinus; closes at age 2
|
|
Fontanelles: Close at age 2 years
|
Anterior and the 2 mastoid fontanelles, because main growth of brain ceased
|
|
Fontanelles: Close at age 6 months
|
Posterior and 2 sphenoid fontanelles
|
|
Craniosynostoses
|
premature closure of sutures
|
|
Microcephaly
|
failure of brain to grow; mental retardation
|
|
Oxycephaly (turricephaly/acrocephaly)
|
tower-like skull caused by premature closure of lamboid & coronal sutures
|
|
Crouzon's Syndrome
|
Dominant genetic condition like oxycephaly, but accompanied w/ malformed face, teeth & ears
|
|
Plagiocephaly
|
asymmetric skull caused by premature closure of lambdoid & coronal sutures on 1 side of skull
|
|
Scaphocephaly
|
Long, narrow skull (in ant/post plane) caused by premature closure of sagittal suture
|
|
Temporal Bone formation: Mastoid Process
|
absent at birth, formed by age 2 yrs, leaving CN VII unprotected emerging from stylomastoid foramen; can be damaged in difficult delivery
|
|
Temporal Bone formation:
Petrosquamous fissure |
Petrous & squamous portions of temporal bone separated by this; opens directly into middle ear, and may remian open until age 20 yrs, leaving route for infection spread from middle ear--> meninges
|
|
Vertebral Column devos from?
|
Mesodermal cells in sclerotome migrating & condensing around the notochord to form a centrum, around the neural tube to form vertebral arches and in the body wall to form costal processes
|
|
Centrum
|
mesodermal cells from sclerotomes that migrate and condense around notocord & form vertebral body of vertebrae
|
|
Vertebral Arches
|
mesodermal cells from sclerotomes that migrate and condense around the neural tube to form vertebral arches, which furhter devo into pedicles, laminae, spinous process, articular processes and transverse processes
|
|
Costal Processes
|
mesodermal cells from sclerotomes that migrate and condense around body wall to form costal processes, which further devo into the ribs
|
|
Intersegmental Position of Vertebrae
|
As mesodermal cells from scelrotome migrate toward notochord & neural tube, they split into cranial & caudal portions; important b/c allows developing spinal nerve a route of access to myotome it innervates
|
|
Caudal Portion of sclerotome fuses with?
|
fuses with cranial portion of succeeding sclerotome, which results in intersegmental position of vertebrae
|
|
Formation of occipital bone
|
Cervical region, caudal portion of 4th occipital sclerotome fuses w/ cranial portion of 1st cervical sclerotome,to form the base of the occipital bone; allows C1 spinal nerve to exit btwn base of bone & C1 vertebrae
|
|
Nucleus Pulposus
|
remnant of embryonic notochord; by 20 yrs, notochordal cells are degenerated & limited to a noncellular matrix only
|
|
Annulus Fibrosus
|
outerrim of fibrocartilage serived from mesoderm btwn vertebral bodies
|
|
Congenital Brevicollis (Klippel-Feil Syndrome)
|
Fusion & shortening of cervical vertebrae, associated w/ shortness of neck, low hairline, limited neck & head motion
|
|
Intervertebrael Disk Herniation
|
Prolapse of nucleus pulposus thru defective annulus fibrosus,nuc. pulp. impinges on spinal roots--> root pain, radiculopathy
|
|
Spina Bifida Occulta
|
Failure of vertebral arches to form or fuse
|
|
Spondylolisthesis
|
Pedicles of vertebral arches fail to fuse w/ vertebral body
|
|
Hemivertebrae
|
Wedges of vertebrae appear that are usually situated laterally btwn 2 other vertebrae
|
|
Vertebral Bar
|
Localized failure of segmentatin on 1 side of column, usu. posterolateral side
|
|
Block Vertebrae
|
Lack of separation btwn 2+ vert., usu in lumbar region
|
|
Cleft Vertebrae
|
Cleft devos in vertebrae, usu. in coronal/ sagittal plane in lumbar region
|
|
Idiopathic Scoliosis
|
Lateral deviation of vert column, involving both deviation and rotation of vert bodies
|
|
Ribs devo
|
costal processes only in thoracic region that grow into ribs; accessory most common & are attached to C7 vertebrae, either ending freely or attached to thoracic cage
|
|
Superior Thoracic Outlet Syndrome
|
Pressure on loer trunk of brachial plexsus & subclavian artery from accessory cervical ribs
|
|
Sternum devo
|
devos from 2 sternal bars that form in ventral wall independently; fuse w/ each other in cranial-caudal direction to form manibrium & xiphoid process at WK8
|
|
Sternal Cleft
|
sternal bars don't fuse completely; not a big problem
|
|
Pectus Excavatum
|
most common chest annom,; depression of chest wall that may extend from manibrium to xiphoid; CP restriction, dropped shoulders, protubernt abdomen, scoliosis; early surg intervention usu needed
|
|
Poland Syndrome
|
Partial/Complete absence of Pectoralis Major; may also have partial agenesis of ribs, ternum, mammary glands, absent lat dorsi & serratus anterior
|
|
Devo of Limbs and Limb Girdles
|
devo from condensations of lateral plate mesoderm in limb bud
|
|
Limb Buds Timeline
|
first visible by WK4, upper appears first, well diff. by WK8, limb tip contains Apical Ecotodermal Ridge, which is inductive to further devo
|
|
Intramembraneous Ossification
|
embryonic mesoderm condenses into sheets of highly vascular CT and directly forms primary ossifciation center; BONES: frontal, parietal, intraparietal of occipital, maxilla, zygomatic, squamous part of temporal, palatine, vomer & mandible
|
|
Endochondral Ossification
|
Embryonic mesoderm forst forms hyaline cartilage model, and THEN develops a primary ossification center at diaphysis; BONES:ethmoid, sphenoid & mastoid of temporal bone, basilar part of occipital bone, incus, malleus, stapes, styloid process, hyoid, bones of limbs, limb girdles, vertebrae, sternum & ribs
|
|
Osteogenesis:
|
occurs by replacement of preexisting CT (from mesoderm); Two types: intramembraneous (direct) and Endochondral (hyaline cartilage 1st)
|
|
Describe how the expression of a gene is regulated
|
-Binding of activators to cell membrane and initiation of various pathways resulting in a transcription cascade
-General transcription factors are recruited during the cascade and upon entering the nucleus, assemble with RNA Polymerase II and bind to the core promoter and enhancer regions of a gene |
|
Describe how a transcription factor increases gene expression.
|
-General transcription factors assemble on all promoter regions transcribed by RNA polymerase II, and are not specified to a specific gene
-Specific transcription factors (enhancer binding proteins) bind to the enhancer sub-region in the promoter region of a specific gene -Co-activators and mediators act to decondense chromatin nucleosomes and allow for transcription factors to gain access to specific promoters |
|
Describe how the secreted protein BMP4 induces gene expression
|
-Bone Morphogenetic Protein-4 binds to ectodermal cells and activates expression of genes which promote epidermal specific genes
-Activation of epidermal genes inhibits the expression of neural specific genes, which are only activated/expressed when BMP4 is absent -BMP4 (Transforming Growth Factor-β superfamily) activates the SMAD family of transcription factors by binding type II TGF-β receptors -Phosphorylated SMAD proteins enter the nucleus and bind to the enhancer sub-region in the promoter region of the epidermal tissue gene -Noggin, chordin and follistatin promote neuronal differentiation by inhibiting the binding of BMP4 to the ectoderm |
|
Describe how retinoic acid gradient specifies rostral-caudal axis formation.
|
-Rostral-caudal axis formation is regulated by transcription factors that are encoded for by the HOX (homeobox) gene
-Retinoic acid diffuses through cell membranes and binds retinoic acid receptors, then enter the nucleus to act as a transcription factor -Retinoic acid bound receptors then bind to specific enhancer elements (retinoic acid response elements) in the promoter region of the HOX gene -HOX genes are present in clusters in the chromosome and have varying degrees are response time and sensitivity to retinoic acid -The retinoic acid gradient (anterior-posterior) provides concentration variation that activates HOX genes at different times/intensity resulting in limb bud formation -Mutation of specific HOX genes can leads to increased/decreased retinoic acid sensitivity, resulting in synpolydactyly |
|
Discuss how sonic hedgehog gradient specifies dorsal-ventral axis formation.
|
-Sonic hedgehog binds cell surface receptors that activate the transcription factor Gli (cubitus interruptus), which enters the nucleus and acts as a transcriptional activator of specific neuronal genes
-The sonic hedgehog gradient provides concentration variation that activates specific genes at different times/intensity resulting in motor neuron differentiation -Cholesterol is present on the sonic hedgehog protein and plays an important role in cell signaling and activation of Gli -Mutation of either the genes that encode for sonic hedgehog or the enzymes that synthesize cholesterol can cause cyclopia |
|
Discuss how teratogens can alter development
|
-Environmental agents that disrupt normal fetal development
-Retinoic acid (Accutane – vitamin A) used to treat severe acne can cause expression of certain HOX genes in cells that do not normally express that gene, resulting in severe hind/mid/fore-brain abnormalities -Thalidomide used as a mild sedative that can inhibit angiogenesis, resulting in various abnormalities to include; limb deformation, heart defects, malformed intestines and missing external ears |
|
Describe how blood vessels are formed
|
-Hemangioblasts (blood vessel and blood cell precusor) are exposed to high concentrations of BPMs early in development and give rise to angioblasts (vascular endothelial cell and hematopoietic stem cell precursor)
-Hematopoietic stem cells are exposed to erythropoietin and differentiate into red blood cells, or lymphocytes with not erythropoietin exposure -Vasculogenesis is the de novo creation of blood vessels from lateral plate mesoderm -Angiogenesis is creation blood vessels via vascular endothelial growth factor (VEGF), which binds receptors on endothelial cells and induces increased expression of genes whose specific protein products are necessary for angiogenesis -Inhibitors of VEGF (Avastin) can be used to treat various types of cancers |
|
Differention
|
-How different genes from the same genetic repertoire are activated at a particular time and place in response to exposure to gradients of molecules or proteins to cause cells to become different from one another
|
|
Morphogens
|
-Diffusible molecules that form time-dependent concentration gradients to specify which cell type will be generated at a specific location
-cell fate can be determined by its location along these gradients, and the set of receptors expressed on their cell surface -ex: retinoic acid (RA), bone morphogenic proteins (BMPs), transforming growth factor beta (TGF-Beta), hedgehogs, & Wnt protein families |
|
Gastrulation
|
-Process of cell movements by which three germ layers and axial orientation are established in embryos
-First sign: appearance of the primitive streak -End: embryo becomes surrounded by ectoderm, endoderm is internalized, and mesoderm betwwn the ectoderm and endoderm. -embryonic ectoderm: epidermis, CNS, PNS, retina, eye, etc. -ex: specific morphogens secreted by the primitive streak alter expression of genes in the overlying ectodermal cells turning them into neural precursor cells. |
|
Coding Region of a Gene
|
-specifies the amino acid sequence of resulting protein
|
|
Promoter Region of Gene
|
-controls how many RNA copies are made
|
|
Core promoter (part of Promoter Region in Gene)
|
-a specific DNA sequence to which RNA polymerase II binds and initiates transcription (or RNA synthesis).
-aka TATA box -RNA pol II can't bind on its own, needs general trascription factors to help it -Once RNA pol is bound it has to be released to start making RNA.So TFIIH (transcription factor)adds phosphate groups to the RNA polymerase to help release it from the DNA promoter and TF cluster, allowing transcription to start -Core promoter by itself makes RNA because RNA pol II and general TFs can't assemble on a promoter associated w/ histone proteins *clinical*: gene for 1st subunit of TFIIH was cloned from humans bc mutations in this gene cause extreme skin sensitivity to sunlight (common cause of DNA damage) & exhibits high incidence of cancer; may cause diseases like xeroderma pigmentosa and Cockayne's syndrome |
|
Define mesenchyme
|
Refers to loosely organized connective tissue present in the embryo regardless of origin. Mesenchyme later differentiates into blood vessels, blood-related organs, and connective tissues.
Embryonic connective tissue (mesenchyme): • Consists of loosely-packed, unspecialized cells set in a gelatinous extracellular matrix • Develops into other types of tissues: connective, bone, cartilage • Develops into other types of structures and systems: blood cells, endothelial cells, smooth muscle cells, circulatory system, lymphatic system. All organs in the body contain mesenchyme. |
|
Define ectomesenchyme
|
Ectomesenchyme has similar properties to mesenchyme. The major difference is that ectomesenchyme is usually considered to arise from neural crest cells,[2] which are a critical group of cells that form in the cranial region during early vertebrate development. Thus, ectomesenchyme plays a critical role in the formation of the hard and soft tissues of the head and neck such as bones, muscles and most importantly the branchial arches.
|
|
How is mesenchyme different than mesoderm?
|
Mesenchyme is not necessarily of mesodermal origin (can also be derived from neural crest cells of ectoderm, as ectomesenchyme); it is loosely orgainized CT in embryo, regardless of origin; Mesoderm is one of the three embryonic germ layers that devos into:
bones most of the circulatory system, including the heart and major blood vessels connective tissues of the gut and integuments mesenchyme mesothelium muscles peritoneum (lining of the coelom) reproductive system urinary system, including the kidneys |
|
Enhancer (part of promoter region in gene)
|
-DNA sequence(s) to which TFs (aka enhancer binding proteins) bind to increase transcription (gene expression)
-used for enhancement of mRNA synthesis |
|
Transcription Factors
|
-Proteins with 2 segments or domains: DNA binding and activation
-amino acids in the DNA binding domain interact w/specific enhancer sequences |