Devo 11

Front 1

what does paraxial mesoderm form

Back 1

the head and somites

Front 2

what is a somite

Back 2

a segmental block or ball of mesoderm formed from paraxial mesoderm adjacent to the notochord (or axial mesoderm). they differentiate initially into sclerotome and dermamyotome and later form dermotome and myotome. they will worm the axial skeleton, all skeletal muscle, dorsal dermis, tendons, joints, and dorsal aortic cells

Front 3

compartment of a mature somite which forms the vertebrae and rib cartilage

Back 3

sclerotome

Front 4

compartment of a mature somite which forms the musculature of the back, rib cage, and vental body wall

Back 4

myotome

Front 5

compartment of a mature somite which contains skeletal muscle progenitor cells and the cells that generate the dermis of the back

Back 5

dermamyotome

Front 6

what cellular process occur during somite formation

Back 6

1. periodicity - time
2. fissure formation (separation of the somites)
3. epithelialization
4. specification
5. differentiation

Front 7

what cellular signaling specifies paraxial mesoderm

Back 7

noggin inhibits bmp signaling

Front 8

what molecular signaling is required for somite formation

Back 8

notch signaling determines the boundary

ventral-to-dorsal signal aligns the posterior border cells

Mesp2/c-Meso1 induces Ephs in the posterior border cells

Ephs induce ephrin in cells across the border - creates a fissure

as the fissure forms a separate signal aligns the cells that will form the new posterior boundary of the somite

ectodermal signal MET act on GTPases to coordinate the transition from mesenchymal to epithelial cell, completing the somite

Front 9

what is the role of notch pathway in somite formation

Back 9

notch signaling will cause the formation of somite boundary. the somite boundaries were formed at the interface between notch expressing and notch nonexpressing areas

also follows a wave like pattern where the notch gene is highly expressed in the posterior region of the forming somite.

notch activates genes in posterior of somite like mesp2/c-meso1

Front 10

what is the notch and mesp2/c-meso1 pathway

Back 10

notch activates mesp2/c-meso1 gene. the protein product is a txn factor that initiates reactions that suppress notch. mesp2/c-meso1 also induces eph a 4 that causes repulsion and separation of somites

notch activates mesp2/c-meso1 which activates a notch supressor and induces eph a4 in the rostral half of the somite which separates the somites and mesp2/c-meso1 in the caudal half of the somite induces the expression of Uncx4.1

Front 11

how are somites specified along the anterior posterior axis

Back 11

the somites are specified according to the hox genes they express. the hox genes are active in the segmental plate mesoderm before it becomes organized into somites. hox genes are activated as somites form and the embryo counts somites in setting the expression boundaries of the hox genes

Front 12

epithelialization

Back 12

occurs after somitic fission
ectodermal signals cause peripheral somitic cells to undergo mesenchymal to epithelial transition by lowering levels of cdc42

stabilized by synthesis of fibronectin and n-cadherin

Front 13

what tissues does the sclerotome become?

Back 13

originate from the ventral-medial cell of the somite (the cells closest to the neural tube and notochord)

becomes mesenchymal cells

ultimately become cartilage cells of the vertebrae and a major part of each rib

Front 14

What signals specify the sclerotome and what is their source?

Back 14

the ventromedial portion of the somite is induced to become the sclerotome by paracrine factors (esp Noggin and SH) secreted from the notochord.
paracrine factors induce the presumptive sclerotome cells to express the txn factor Pax1, which is required for their epithelial-to-mesenchymal transition and subsequent differentiation into cartilage

Front 15

what tissues does the dermamyotome become

Back 15

the epithelial portion of the somite

myotomes (cells in the two lateral portions closest to and farthest from the neural tube that form muscle cells)

dermatome (central region of the somite will form back dermis and several other derivatives)

Front 16

What signals specify the dermamyotome and what is their source?

Back 16

Wnt6 coming forom the epiderms

the epithelial-to-mesenchymal transition is regulated by NT3 and Wnt1.

Front 17

What signals specify the myotome and what is their source?

Back 17

factors from the neural tube - probably wnt1 and wnt3a from the dorsal region and low levels of SH from the ventral region

noggin inhibits BMP signaling, and promotes myoblast differentiation

Front 18

what happens if noggin is ablated in a chick embryo

Back 18

eye defect
thin abdominal wall and organs are herniated
reduced somatic musculature - reduced myosin in muscles

Front 19

how do muscles form

Back 19

myotome cells are determined by paracrine factors. committed myoblasts divide in the presence of growth factors (fgfs) but show no obvious muscle-specific proteins. when growth factors are all used up, the myoblasts cease dividing, align with eachother, fuse into myotubes. myotubes become organized into muscle fibers that spontaneously contract.

Front 20

explain the steps to endochondral ossification

Back 20

Mesenchymal cells commit to becoming cartilage cells ( chondrocytes). ( B) Committed mesenchyme condenses into compact nod-ules. ( C) Nodules differentiate into chondrocytes and proliferate to form the cartilage model of bone. ( D) Chondrocytes undergo hypertrophy and apoptosis while they change and mineralize their extracellular matrix. ( E) Apoptosis of chondrocytes allows blood vessels to enter. ( F) Blood vessels bring in osteoblasts, which bind to the degenerating cartilaginous matrix and deposit bone matrix. ( G) Bone formation and growth consist of ordered arrays of proliferating, hypertrophic, and mineral-izing chondrocytes. Secondary ossification centers also form as blood vessels enter near the tips of the bone.

Front 21

Thick bands of embryonic mesoderm imme-diately adjacent to the neural tube and notochord. In the trunk, paraxial mesoderm gives rise to somites, in the head it gives rise to the connective tis-sues and musculature of the face.

Back 21

paraxial mesoderm

Front 22

Mesoderm immediately lateral to the paraxial mesoderm. It forms the outer ( cortical) portion of the adrenal gland and the urogenital system, consisting of the kidneys, gonads, and their associated ducts.

Back 22

intermediate mesoderm

Front 23

Blocks of mesodermal cells in the ventromedial half of each somite that will differentiate into the vertebral bodies and intervertebral discs of the spine and ribs. They are also critical in patterning the neural crest and motor neurons.

Back 23

sclerotomes

Front 24

Putative muscle stem cell found within the basal lamina of mature myofibers that can respond to injury or exercise by proliferating into myogenic cells that fuse and form new muscle fibers.

Back 24

satellite cell

Front 25

Greek syn, “ connected.” Derived from the most dorsal sclero-tome cells, which express the scleraxis gene and generate the tendons.

Back 25

syndetome

Front 26

Portion of the somite that gives rise to skeletal muscles. The _____ has two components: the primaxial component, closest to the neural tube, which forms the muscula-ture of the back and rib cage, and the abaxial component, away from the neural tube, which forms the muscles of the ventral body wall.

Back 26

myotome

Front 27

muscle precursor cell

Back 27

myoblast

Front 28

a member of the tgf-b family of paracrine factors that negatively regulates muscle development. Genetic defects in the gene or its negative regulatory miRNA cause huge muscles in some mammals, including humans.

Back 28

myostatin

Front 29

The second kidney of the amniote embryo, induced in the adjacent mesenchyme by the middle portion of the nephric duct. It func-tions briefly in urine filtration in some mammalian species and mesonephric tubules form the tubes that transport the sperm from the testes to the urethra ( the epididymis and vas deferens).

Back 29

mesonephros

Front 30

An area of mesenchyme, derived from posterior regions of the intermediate mesoderm, involved in mesenchymal-epithelial interactions that generate the metanephric kidney and will form the secretory nephrons

Back 30

metenephrogenic mesenchyme

Front 31

Dorsolateral portion of the somite that contains skeletal muscle progenitor cells, ( including those that migrate into the limbs) and the cells that generate the dermis of the back.

Back 31

dermamyotome

Front 32

The intercostal musculature between the ribs and the deep muscles of the back, formed from those myoblasts in the myotome clos-est to the neural tube.

Back 32

primaxial muscles

Front 33

Afibrous sheath contain-ing connective tissue, capillaries, and bone progenitor cells and that covers the developing and adult bone.

Back 33

periosteum

Front 34

Formed during the fourth phase of endochon-dral ossification, when the chondro-cytes, under the influence of the tran-scription factor Runx2, stop dividing and increase their volume dramatical-ly.

Back 34

hypertrophic chondrocytes

Front 35

Bone formation directly from mesenchyme. There are three main types of ______ bone: sesamoid bone and periostal bone, which come from mesoderm, and dermal bone which originate from cranial neural crest- derived mesenchymal cells.

Back 35

intramembranous ossification

Front 36

Bone for-mation in which mesodermal mes-enchyme becomes cartilage and the cartilage is replaced by bone. It charac-terizes the bones of the trunk and limbs.

Back 36

endochondral ossification

Front 37

Paired epithelial branches induced by the metanephro-genic mesenchyme to branch from each of the paired nephric ducts. Ureteric buds will form the collecting ducts, renal pelvis, and ureters that take the urine to the bladder.

Back 37

ureteric buds

Front 38

The tendon- forming cells of the syndetome can be visualized by their expression of the ___ gene

Back 38

scleraxis

Front 39

how are tendons formed

Back 39

myotome secretes FGF onto the sclerotome. sclerotome in the presence of fgf secretes scleraxix which activates tendon genes.

sclerotome in the presence of shh (from the notochord and the floorplate) secretes sox 9, which activates sox5 and sox6, which activate cartilage genes and inactivate scleraxis. shh also inhibits scleraxis

the tendons associate with muscles directly above them and with the skeleton

Front 40

mesenchyme induced by the anterior region of the pronephric duct to form these tubules of the initial kidney

Back 40

pronephros

Front 41

how do kidneys form

Back 41

The original tubules, constituting the pronephros, are induced from the nephrogenic mesenchyme by the pronephric duct as it migrates caudally. ( B) As the pronephros degenerates, the mesonephric tubules form. ( C) The final mammalian kidney, the metanephros, is induced by the ureteric bud, which branches from the nephric duct

As the ureteric bud enters the metanephrogenic mesenchyme, the mesenchyme induces the bud to branch. ( B– G) At the tips of the branches, the epitheli-um induces the mesenchyme to aggregate and cavitate to form the renal tubules and glomeruli ( where the blood from the arteriole is fil-tered). When the mesenchyme has condensed into an epithelium, it digests the basal lamina of the ureteric bud cells that induced it and connects to the ureteric bud epithelium. A portion of the aggre-gated mesenchyme ( the pretubular condensate) becomes the nephron ( renal tubules and Bowman’s cap-sule), while the ureteric bud becomes the collecting duct for the urine.

Front 42

what signals are critical for kidney development

Back 42

paraxial mesoderm signals to the intermediate mesoderm

intermediate mesoderm is signaled to become intermediate mesoderm by the BMP gradient

paraxial mesoderm secretes lim1, pax2 and pax8 that signal the intermediate mesoderm to form the kidney

Front 43

what signals induce ureteric bud growth

Back 43

GDNF and its receptors. cells expressing ret form the tips of the ureteric bud.

Front 44

importance of wnts and the formation of nephrons

Back 44

wnt9b is found in the stalk of the ureteric bud, wnt11 is found at the tips. wnt9b induces metanephrogenic mesenchyme to condence and wnt 11 partitions the metanephrogenic mesoder to induce branching of th eureteric bud.