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Systems-based Embryology (cardiovascular system (vascular development…

- - - - consisting bars of mesenchymal tissue
        
        each having their own
        
        artery
        
        cranial nerve
        
        muscle element
        
        cartilage bar/skeletal element
      - separated by pharyngeal pouches and clefts
        
        endoderm of pharyngeal pouches
        
        gives rise to
        
        part of middle ear
        
        pouch 1
        
        middle ear cavity
        
        auditory tube
        
        number of endocrine glands
        
        pouch 3
        
        inferior parathyroid gland
        
        thymus
        
        pouch 4 and 5
        
        superior parathyroid glands
        
        ultimobranchial body
        
        pouch 2
        
        stroma of the palatine tonsil
        
        patterning of skeletal elements
        
        regulation
        
        epithelial-mesenchymal signalling
        
        endoderm of pouches signals the adjacent mesoderm
        
        mesenchymal gene expression
        
        2 more items...
        
        pharyngeal cleft
        
        gives rise to
        
        ear canal
      - give the head and neck region their characteristics
        
        4th week
      - thyroid gland originates from an epithelial proliferation
        
        at the floor of the tongue
  - - - determine the size and growth of
        
        mandible
    - - around the other nasal placodes
        
        .
        
        upper lip
        
        occurs by fusion of two maxillary prominences with two medial nasal prominences
        
        intermaxillary segment is formed by merging of the two medial nasal prominences in the midline
        
        components
        
        philtrum
        
        upper jaw component
        
        palatal component
        
        palate
        
        fusion of palatal shelves
        
        forms from maxillary prominence
        
        creates hard and soft palate
        
        partial fusion results in clefts
        
        nose
        
        derived from
        
        frontonasal prominence
        
        forms the bridge
        
        medial nasal prominences
        
        crest and tip
        
        lateral nasal prominence
        
        alae
  - - - epithelial to mesenchymal interactions
        
        oral epithelium
        
        neural crest derived mesenchyme
- - - - visceral mesoderm
    - - visceral mesoderm
  - - - paraxial mesoderm
        
        somites
        
        cervical towards caudal parts
        
        somitomeres
        
        head region
  - - - some cross the lateral somatic frontier
        
        to parietal layer
        
        lateral somatic frontier separates two mesodermal domains
        
        primaxial
        
        surrounds neural tube
        
        does not cross the LSF
        
        contains only somite derived cells
        
        paraxial mesoderm derived
        
        give rise to
        
        intercostal muscles
        
        shoulder girdle muscles
        
        muscles of the back
        
        abaxial
        
        parietal layer of lateral plate mesoderm
        
        paraxial cells that migrate from DML area
        
        give rise to
        
        neck muscles
        
        abdominal wall
        
        internal abdominal muscles
      - signalling
        
        lateral plate mesoderm signals via BMPs
        
        .
        
        overlying ectoderm signals via WNT
        
        Induce VLL cells
    - - notochord expresses SHH and WNT
        
        induces DML cells
- - - - head region
- - - - buds become visibly distiguishable
        
        spinal nerves penetrate into the mesenchyme
        
        flexor nerves
        
        ventral branches
        
        extensor nerves
        
        dorsal branches
        
        in contact with the mesenchyme
        
        prerequisite for the complete functional development
        
        provides sensory innervation for dermatomes
        
        Limb outgrowth is initiated by FGF10
        
        BMPs expressed in ventral ectoderm
        
        induce the formation of AER #
        
        RADICAL FRINGE
        
        induces SER2
        
        1 more item...
        
        restricts AER to the distal tip
      - Specific spinal segments determined by HOX genes initiate the limb bud formation
    - - terminal portion of buds
        
        flattens and separates from proximal segment
        
        second constriction
        
        divides proximal portion into two segments
        
        main parts of extremities become distiguishable
        
        fingers and toes form via AER area apoptosis divides in 5 protursions
        #
        
        1 more item...
    - - limbs rotate
  - - - will form
        
        bones
        
        CT
        
        covered by cuboidal ectoderm
        
        distal border of the limb
        
        thickens and forms
        
        Apical Ectodermal Ridge=AER
        
        inductive influence
        
        1 more item...
- - - - migrate to visceral layer of lateral plate mesoderm DAY 16
        
        horseshoe-shaped cluster of cells (Primary Heart Field PHF)
        
        form
        
        ventricles
        
        part of right ventricle
        
        left ventricle
        
        4th week
        
        primitive ventricles begin to expand
        
        1 more item...
        
        atria
        
        formation of left atrium
        
        expands via caudal end of dorsal mesocardium proliferating
        
        1 more item...
        
        develops by expansion and incorporating pulmonary vein
        
        right atrium
        
        enlarges by incorporation of the right sinus horn
        
        1 more item...
        
        atrioventricular canals
        
        atrioventricular cushions
        
        1 more item...
        
        induced by
        
        underlying pharyngeal endoderm
        
        to form
        
        cardiac myoblasts and blood islands that will form blood cells and vessels
        
        1 more item...
        
        CARDIOGENIC REGION
        
        intraembryonic cavity will result in formation of pericardial cavity
        
        anterior to oropharyngeal membrane and neural plate
        
        CNS extends over cardiogenic region as it grows so fast
        
        oropharyngeal membrane is pulled forward
        
        1 more item...
        
        initiated by anterior endoderm underlying heart progenitor cells
        
        causes cells to become myoblasts and vessels
        
        BMP secreted by this endoderm
        
        1 more item...
        
        blood islands
        
        appear bilaterally and parallel, close to midline
        
        give rise to dorsal aorta
        
        expands and forms a future outflow tract and ventricular regions
        
        heart becomes a continuous expanded tube consisting of an inner endothelial lining an outer myocardial layer
        
        pumping blood out from the first aortic arch into the dorsal aorta its cranial pole
        
        developing heart bulges more into pericardial cavity
        
        tube remains to attached to the dorsal side of pericardial cavity by a fold of mesodermal tissue
        
        dorsal mesocardium
        
        1 more item...
        
        inducing NKX2.5
        
        NKX2.5 requires BMP 2 and 4 from lateral plate mesoderm
        
        WNT from neural tube must be BLOCKED by CRESCENT and CERBERUS inhibits heart formation
        
        BMP upregulates FGF8, which is important for cardiac-specific proteins
        
        venous portion is specified by RA
        
        directs to become caudal cardiac structures
        
        cardiac looping
        
        PITX2 left side of lateral plate
        
        NKX2 upregulates HAND1 and HAND2
        
        ventricle inducing factor
        
        lengthening of the tract
        
        SHH
    - - caudal end of the heart
        
        Secondary Heart Field (SHF)
        
        form
        
        outflow tract
        
        remainder of right ventricle
        
        truncus arteriosus
        
        patterned by laterality signaling
        
        regulate neural crest cell contributions to septation of the outflow tract
        
        caudal regions merge except the caudalmost ends
        
        venous drainage in caudal part #
        
        .
        
        development of sinus venosus
        
        receives blood from three sources
        
        umbilical vein
        
        vitelline vein
        
        common cardinal vein
        
        left sinus horn loses its meaning
        
        1 more item...
        
        formation of cardiac septa
        
        two major septa are formed between 27 and 37 days
        
        endocardial cushions
        
        3 more items...
  - - - week 5
        
        truncus swellings
        
        gradually tubercles hollow out their upper surface to form a flat valve
      - derive from neural crest cells
    - - sinus is incorporated into the right atrium=sinuatrial node
      - AV node and bundle of his
        
        derived from
        
        myocardial cells
        
        in the left wall of sinus venosus
        
        incorporated into right atrium
        
        cells lie in their final destination
        
        atrioventricular canal
  - - - vasculogenesis
        
        major vessels
      - angiogenesis
        
        remainder of vasculature
      - regulating factors
        
        VEGF
    - - week 5
        
        pharyngeal arches receive a nerve and an artery
        
        aortic arches
        
        arise from aortic sac
        
        embedded in mesenchyme of pharyngeal arches
        
        neural crest cells contribute the covering of vessels
        
        smooth muscle and CT
        
        getting signals from end and ecto
        
        FGF8
        
        1 more item...
        
        left-right decisions
        
        1 more item...
        
        terminate to dorsal aortae
        
        5 forms but not existing simultaneously
        
        arches
        
        3rd arch
        
        forms COMMON CAROTIC ARTERY
        
        external CA is a sprout of 3rd aortic arch
        
        remainder of internal CA is formed by cranial portion of dorsal aorta
        
        first part of internal CA
        
        carotic duct
        
        disappears
        
        4th aortic arch
        
        persist on both sides
        
        yet different to each other
        
        2 more items...
        
        5th aortic arch
        
        never forms or degenerates quickly after formation
        
        6th aortic arch
        
        pulmonary arch
        
        grows towards lung bud
        
        sides
        
        2 more items...
        
        are pushed further to caudal direction as cephalic folding, growth of the forebrain and elongation of the neck happens
      - vitelline arteries
        
        gradually fuse
        
        form the arteries in dorsal mesentery of the gut
        
        ultimately
        
        celiac and sup mesenteric arteries
      - umbilical arteries
        
        initially paired branches of dorsal aorta
        
        ultimately loses its origin while connects to common iliac artery
        
        supply foregut, midgut, hindgut
      - coronary arteries
        
        derived from epicardium
        
        some cells go through EMT
        
        induced by myocardium
        
        newly profiled mesenchymal cells
        
        contribute to
        
        endothelial cells of coronary arteries
        
        1 more item...
        
        smooth muscle cells of coronary arteries
        
        1 more item...
    - - vitelline veins
        
        5th week
        
        carrying blood from yolk sac to sinus venosus
        
        liver cords growing into the septum
        
        hepatic sinusoids
        
        extensive vasculature network
        
        PORTAL SYSTEM
      - umbilical vein
        
        originating from chorionic villi
        
        carrying oxygenated blood to embryo
        
        disappears after birth
      - cardinal veins
        
        draining the embryo body
        
        forms CAVAL system
  - - - from placenta (80%sat) returning via umbilical vein
      - small amount enters liver sinusoids
      - when entering the right atrium
        
        blood goes through foramen ovale
        
        to left atrium
        
        resistance of pulmonary vessels is high
        
        blood bypasses via ductus arteriosus
        
        aorta
        
        1 more item...
      - blood mixes with desaturated blood
        
        three potential places
        
        inf vena cava
        
        carries deoxy blood from lower extremities
        
        right atrium
        
        deoxy blood from upper limbs and head region
        
        liver
        
        mixture of blood returning from the portal system
    - - placental blood flow stops
      - ductus arteriosus closes
        
        blood flows to lungs
        
        raises pressure in right atrium
        
        obliteration takes 3 months
        
        forms a ligament
      - foramen ovale closes
        
        due to increased pressure in left atrium
        
        first breath presses the septum primum against septum secundum
        
        during first days it is reversible
        
        fusion of two septa within one year
        
        crying creates a shunt
        
        cyanotic periods
      - closure of umbilical arteries
        
        smooth muscle cell tissue in their walls contracts
        
        lumen grows to CT in 2-3 months
        
        distal parts form medial umbilical ligaments
        
        proximal parts remain open as sup vesicle arteries
      - closure of umbilical veins
      - ductus venosus closes
- - - - regulation
        
        PROX1
        
        upregulates lymph vessel genes
        
        down regulates blood vesselgenes
    - - two iliac
      - retroperitoneal
      - cisterna chyli
      - two jugular
      - CONNECTED BY NUMEROUS CHANNELS
        
        2 main channels
  - - - both thoracic ducts
      - the cranial part of the left thoracic duct
      - distal part of the right thoracic duct
- - - - dependent of an increase of RA :explode:
        
        produced by adjacent mesoderm
        
        causes up-regulation of transcription factor TBX4
        
        expressed in endoderm of the gut tube
        
        induces bud formation
        
        continued growth and differentation
        
        epithelium of internal lining of the larynx, lungs, trachea and bronchi
        
        endodermal origin
        
        cartilage, muscle tissue and CT
        
        visceral mesoderm surrounding foregut
      - initially
        
        foregut and lung bud are in open communication
        
        as lung diverticulum expands caudally
        
        two longitudinal ridges separate the the lung bud from foregut
        
        forming a septum between trachea and foregut
        
        tracheoesophageal septum
        
        3 more items...
  - - - structures
        
        cartilage and muscles
        
        mesenchyme from 4th and 6th pharyngeal arch
        
        rapid proliferation
        
        formation of laryngeal cartilages
        
        muscles are innervated by vagus nerve
        
        lining
        
        endoderm
        
        proliferates rapidly
        
        temporary occlusion of lumen
        
        vacuolization and recanalization
        
        1 more item...
    - - when separating from foregut
        
        formation of bronchial buds
        
        5th week
        
        enlargement of bronchi
        
        left
        
        2 secondary lobes
        
        1 more item...
        
        right
        
        3 secondary lobes
        
        1 more item...
        
        space for lungs in pericardioperitoneal canals is narrow
        
        gradually expand
        
        6 more items...
- - - - foregut
        
        esophagus
        
        4 weeks
        
        lung buds appear
        
        tracheoesophageal septum gradually separates foregut and trachea
        
        esophagus is short at first
        
        as heart and lungs descent, it lengthens rapidly
        
        muscular coat derived from visceral mesoderm
        
        striated + vagus
        
        smooth + splanchnic plexus
        
        stomach
        
        4th week
        
        dilation of foregut
        
        positional changes
        
        rotates 90 degrees clockwise
        
        growth simultaneously
        
        curves of the stomach
        
        attached to the dorsal mesogastrium and ventral mesogastrium
        
        rotation forms mental bursa
        
        2 more items...
        
        duodenum
        
        terminal foregut+cephalic midgut
        
        as stomach rotates, duodenum takes on the form of a C-shaped loop
        
        location is fixed by dorsal mesoduodenum fuses into adjacent peritoneum
        
        2nd month
        
        lumen of the duodenum is obliterated
        
        recanalized shortly after
        
        liver and gallbladder
        
        development
        
        3th week
        
        liver primordium
        
        endodermal epithelium
        
        liver bud
        
        3 more items...
        
        pancreas
        
        formed by two buds
        
        dorsal
        
        duct obliterates or remains as a small channel
        
        ventral
        
        close to bile duct
        
        major papilla
        
        finally ventral comes in immediate closeness to dorsal
        
        fusion
        
        as duodenum rotates to C-shape figure
        
        ventral pancreatic bud moves shifting the entrance of the duct closer to bile duct
        #
        
        3rd month
        
        islets of Langerhans develop from parenchymatous pancreatic tissue
        
        insulin secretion begins in 5th month
        
        molecular development regulation
        
        notochord and endothelium of the dorsal aorta
        
        express
        
        FGF2 and ACTIVIN
        
        1 more item...
        
        repress
        
        SHH
        
        1 more item...
      - hindgut
        
        gives rise to
        
        distal third of transverse colon
        
        descending colon
        
        sigmoid
        
        upper part of anal canal
        
        anorectal canal
        
        cloaca region
        
        endoderm-lined cavity
        
        1 more item...
        
        covered at its ventral boundary by surface ectoderm
        
        1 more item...
        
        endoderm of the hindgut
        
        internali lining of
        
        bladder
        
        urethra
      - midgut
        
        remains connected to yolk sac until fusion
        
        5 week embryo
        
        suspended from dorsal abdominal wall by short mesentery
        
        communicates with yolk sac
        
        via vitelline duct
        
        adult
        
        midgut begins immediately distal to entrance of the bile duct into duodenum
        
        terminates at junction of the proximal 2/3 of transverse colon
        
        rapid elongation of the gut
        
        primary intestinal loop
        
        remains open connection with yolk sac
        
        via vitelline duct
        
        cephalic limb of the loop
        
        distal duodenum, jejunum, part of ileum
        
        rapidly elongates during 5th week
        
        physiological herniation
        
        caudal limb
        
        lower portion of ileum, the cecum, the appendix, ascending colon, proximal 2/3 of transverse colon
        
        rotation of midgut
        
        primary intestinal loop rotates around the axis formed by the superior mesenteric artery
        
        as rotation goes on, elongation occurs simultaneously
        
        coiled loops
        
        retraction of the Midgut
        
        10th week
        
        herniated intestinal loops retract to abdominal cavity
        
        first
        
        proximal portion of jejunum
        
        2 more items...
        
        last
        
        cecal bud
        
        1 more item...
  - - - important in development of head and neck region
    - - after pharyngeal tube
      - extends as far as liver outgrowth
    - - caudal to liver bud
      - extends to the junction of colon
    - - from left third of the transverse colon to cloacal membrane
    - - the specific cells of glands
        
        hepatocytes
      - endocrine and exocrine cells
    - - CT of the glands
      - CT
      - muscles
      - peritoneal components of the wall of the gut
    - - concentration gradient of RA
        
        pharynx exposed to little or no RA
        
        Colon sees highest RA
      - specific transcription factors for specific tissues
        
        SOX2
        
        specifies esophagus and stomach
        
        PDX1
        
        duodenum
        
        CDXC
        
        small intestine
        
        CDXA
        
        large intestine and rectum
        
        carried out via dialogue between endoderm and visceral mesoderm adjacent to gut tube
        
        initiated by SHH
        
        establishes a nested expression of HOX genes
        
        in mesoderm
        
        instructing the endoderm to form various components of different regions #
  - - - enclose organs
        
        intraperitoneal organs
      - connect organs to peritoneum
    - - CT narrows
        
        parts of gut are suspended from the abdominal wall by DORSAL MESENTERY
        
        forms
        
        greater omentum
        
        mesoduodenum
        
        dorsal mesocolon
        
        VENTRAL MESENTERY
        
        only in terminal part of esophagus
        
        derived from septum transversum
        
        divided into
        
        lesser omentum
        
        falciform ligament
- - - - kidney systems
        
        three overlapping systems are formed in cranial-caudal sequence in embryonic development
        
        pronephros
        
        nonfunctional
        
        4th week
        
        cell groups with 7-10 cells
        
        vestigial excretory units
        
        1 more item...
        
        disappeared at the end of 4th week
        
        mesonephros
        
        may function a short period
        
        derived from intermediate mesoderm
        
        excretory tubules appear
        
        lenghten
        
        looping
        
        1 more item...
        
        disappeared by second month
        
        wholly disappear in female embryos
        
        some structures remain in male as these participate in formation of the genital system
        
        metanephros
        
        permanent kidney
        
        collecting system
        
        collecting ducts develop from ureteric bud
        
        3 more items...
        
        excretory system
        
        each collecting tubule is covered at its distal end by metanephric tissue cap
        
        1 more item...
        
        molecular regulation
        
        epithelial-mesenchymal interactions
        
        3 more items...
        
        conversion from mesenchyme to epithelium for nephron formation
        
        1 more item...
        
        ascent of the kidney
        
        diminution of body curvature
        
        growth of the body
        
        2 more items...
        
        appears in 5th week
    - - chromosomal
        
        Y-chromosome
        
        contains Sex-determining Region on Y
        
        testis-determining gene
        
        initiates a cascade of male sex organs
      - sex characteristics at 7th week
        
        gonads appear as longitudinal ridges
        
        germ cells appear in 6th week of development
        
        primordial germ cells
        
        originate from epiblast
        
        migrate through primitive streak
        
        1 more item...
        
        formed as
        
        (1) epithelia proliferates
        
        (2) mesenchyme condenses beneath
- - - - week 3
  - - - fuse into neural tube
        
        caudal end closes 28
        
        cranial end closes day 25
  - - - brain
        
        parts
        
        stem
        
        cerebellum
        
        cerebral hemispheres
        
        three vesicles
        
        rhombencephalon
        
        metencephalon
        
        myelencephalon
        
        cerebellum
        
        pons
        
        mesencephalon
        
        resembles the spinal cord
        
        basal efferent
        
        alar afferent
        
        prosencephalon
        
        diencephalon
        
        thin roof plate
        
        thick alar plate
        
        2 more items...
        
        telencephalon
        
        cerebral hemispheres
        
        1 more item...
        
        ventricular system
        
        from SC to 4th ventricle in rhombencephalon
        
        patterning
        
        HOX
        
        organizing centers
        
        anterior neural ridge
        
        rhombencephalic istmus
    - - spinal cord
        
        basal plate
        
        motor neurons (soma inside the plate)
        
        alar plate
        
        sensory neurons (soma inside the ganglia)
        
        floor plate
        
        induced by SHH
        
        ventralizes
        
        roof plate
        
        BMP4 and BMP7
        
        spinal nerves from each segment