Development of the Pig Embryo

Development of the Pig Embryo (Anterior) Later Stages of Development of Pig Embryo follow pattern of development for the chick except for the following: 1. The formation of extraembryonic membranes 2. Additional role of allantois and or blood vessels in: a. Excretion b. Nutrition c. Gaseous exchange thru placenta 3. Relationship of chorion and uterine endometrium in placenta WHOLE MOUNT Info before the sections: -

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Flexures and bending observed in the pig: o Cranial o Cervical o Caudal o Bending in lumbar and sacral regions  Due to limited space in uterine cavity  Results in formation of curved embryo (resembling letter C) Internal structures can be seen because of the THIN SKIN (sarap chicharon hahaha) Prosencephalon o Olfactory Vesicles  Outgrowths at prosencephalon  At rostral end of the head o Optic Vesicle  Ventrolateral to olfactory vesicle  swellings o Otic Vesicle  Posterior  Lateral to myelencephalon 1st and 2nd Visceral Arches are prominent o Mandibular (1st) arch

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 Provides basics of lower jaw  Posterior to maxillary processes  Below naso-medial processes o Hyoid (2nd) arch  Source of hyoid skeleton Hyomandibular cleft o Between the 1st and 2nd visceral arches 3rd and 4th Visceral arches o Not distinct o Sunk deeper into the embryo in the Cervical Sinus Somites o From trunk region to tail o Superficial bulges Position of Heart, Liver and Mesonephros o Observed on lateral and ventral part of body Paddle-shaped limb pads o Close to a region (not specified) and close to a tail region o So there are 2 paddle – shaped limb pads Mammary Ridges o Dorso- lateral swellings o Between levels of forelimb and hindlimb buds

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Transverse Section

**Note: Because of the flexions (cranial, cervical and caudal), the most cranial region region of specimen will not be observed in the first few sections - Level of the Myelencephalon Name and Description

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Location

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Function / Cavity

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Has wide ventricle IV o Becomes narrower as it reaches level of spinal cord -

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Fate

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Derived From/ Arises From -

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Mesocoel/Cerebral Aqueduct of Sylvius o Leads to ventricle of metencephalon via the Isthmus - Isthmus o Narrow constriction Both sides of wider - Auditory (Otic) Vesicle o Cavity beside duct area of seen posteriorly myelencephalon Lateral and parallel to - Nerve separates into 2 myelencephalon posteriorly: o DORSAL  Dorso-lateral to myelencephalon  Jugular ganglion lies lateral as it is moved posteriorly o VENTRAL  Ventral to above - Level of the Mesencephalon and Metencephalon

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Myelencephalon Thin anterior wall Thick posterior wall Neuromere marking seen posteriorly

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Neuromeres Undulations Metencephalon - Thick – walled brain region - V - shaped Mesencephalon - Thick - walled

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Endolymphatic Ducts Cavities

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Spinal Accessory Nerve (XI) Long, fibrous strand

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Wall of myelencephalon Lower part of 4th ventricle Occupies lowermost portions of brain

**Find out what the ventricle is called** -

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Name and Description

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Spinal Accessory Nerve (XI) - Dorsal portion almost faded o Frorlep’s ganglion observed instead of dorsal portion - Ventral Portion o Still lies ventral to above Jugular Ganglion - First ganglion of Vagus Nerve (X) observed - Large ganglionic mass -

Location

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Superior Ganglion First ganglion of glossopharyngeal nerve (IX) Smaller than jugular ganglion Auditory (Otic) Vesicle continuous with

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Lateral to 11th neuromere of myelencephalon Observed before frorlep’s ganglion -

Between jugular ganglion and auditory vesicle

Fate

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Nodose Ganglion - Second ganglion of vagus nerve Frorlep’s Ganglion - Both sides of brain - Small but prominent caudal to roots of ganglion spinal accessory nerve (XII) Hypoglossal Nerve (XII) -

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Function / Cavity/Takes Place

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Streaks of vagus nerve takes place of ganglion posteriorly

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Takes place of streaks of vagus nerve as it fades out -

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It is the hypoglossal nerve if the frorlep’s ganglion is in view

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replaced by a second ganglion of the IXth nerve (petrosal ganglion)

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Future utriculus of inner ear now in view Rudiment of

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In Posterior Section; represented by

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ORIGINATES: Minute branches of nerves from ventrolateral wall of Myelencephalon -

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endolymphatic duct

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Facial Nerve (VII) bundles of fibers from myelencephalon to its ganglion, the geniculate Auditory Nerve (VIII) - best observed posteriorly Auditory Ganglion -

Posterior Semicircular Canal o Projection on top of future utriculus - Rudiment of Anterior Semicircular Canal o Projection on bottom of future utriculus

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future sacculus - Future Sacculus o no projection and connection with endolymphatic duct o closely related to auditory nerve -

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Below auditory vesicle -

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Occulomotor Nerve (III) Small bodies of nerve fibers

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In Mesenchyme At level when metencephalon has separated from mesencephalon

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Semilunar (Gasserian) Ganglion - Ganglion of Trigeminal Nerve (V) - Biggest ganglion so far of all cranial ganglia Trigeminal Nerves (V) Basilar Artery - Small blood vessels

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- Associated with metencephalon -

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Lying in midline Beneath metencephalon

Auditory Ganglion + Geniculate ganglion = Acoustico – Facialis ganglion

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ARISES FROM: Myelencephalon

ARISES FROM: Metencephalon

Abducens Nerve (VI) - Small nerves

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Growing out on sides of myelencephalon and future sacculus

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Name and Description -

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ARISES FROM: Myelencephalo

Level of Pharyngeal Cavity and Diencephalon

Location

Pharyngeal Cavity Appears divided because of cranial flexure o Anterior Portion  Ventral Cavity leads to stomodeu m o Posterior Portion  Dorsal Cavity leads to Trachea & Stomodeu m

TONGUE RUDIMENTS A. Tuberculum Impar - Median swelling B. Lateral Tongue Swellings - Paired elevations C. Copula - swellings -

- Disappears posteriorly

At lower portion of bridge leads to stomodeum Both sides of tuberculum impar On Top of tuberculum impar Occupies medial pat of visceral arch 2

Function / Cavity/Takes Place - Bridge of mesenchyme o Separates anterior and posterior portion o First Few of Bridge shows paired 1st pharyngeal (branchial) arches connected o Broadens, also shows 2nd pharyngeal arches connected -

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Protrude to cavity leads to trachea and esophagus POSTERIORLY: o Union of 3rd

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Fate

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Pati manual tinanong ano fate ng tongue rudiment amputa

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ARISES FROM Pharyngeal floor at bases of 2nd & 3rd Branchial arches

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- Epiglottis Median swelling

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- On top of connected paired 3rdpharyngeal arches -

First Pharyngeal Pouch - Bounded by Mandibular arch lower portion - Hyoid arch on upper portion - Maxillary Process - Prominence or outgrowth below mandibular arch

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- Rathke’s Pouch Appears like a cavity on top of the diencephalons which opens to stomodeum

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Edi tongue. Tongue rudiment eh? kaloka

Hyomandibular Cleft o Where pouch opens to outside posteriorly

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Maxillary & Mandibular Process DERIVED FROM - 1st Branchial Arch ARISES FROM - Dorsal evagination of stomodeum extends under diencephalon to infundibulum -

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- Diencephalon Laterally compressed brain - SPINAL CORD - Spinal nerves basis of differentiation for myelen and spinal cord

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pharyngeal arch observed o This widens mesenchyme bridge Took place of copula

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bears ventricle III

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A. FLOOR PLATE - On top of notochord Thin wall of spinal cord

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B. BASAL PLATE

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Indicates fusion of

C. ROOF PLATE

What is the fate of the Infundibulum? Hypophysis (??) pls confirm

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Most dorsal cavity No marked boundary separating it from myelencephalon Corresponds to neural groove during neural plate stage -

- Lies antero-ventrally on sides of floor plate -

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DERIVED FROM 3rd and 4th pharyngeal arches

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Thin mid-dorsal wall -

D. ALAR PLATE

- Lies postero-ventrally on both sides of roof plate E. SULCUS LIMITANS - Depression on inner wall - Nodose - Big pair of ganglia on top Ganglion of both sides of cavity - 2nd ganglion of Vagus - Leads to trachea and Nerve esophagus Anterior (Cranial) - Close to top of nodose Cardinal (Precardinal ganglia Vein) - Pair of ganglia

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Dorsal Aorta Pair of artery

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Anterior Sections Shows: - Paired big vessels between posterior section of sacculus Posterior Sections Shows: - Paired vessels dorsally located and close to epidermis -

- Close to anterior cardinal vein and nodose ganglion - Towards inner side of body of embryo


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Spinal Ganglia

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4th Pharyngeal Pouches

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Level of Pharynx

Location

On dorsal roots of spinal nerves On both sides of inverted u – shaped

Marks boundary between alar and basal plates

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neural folds Lamina Terminalis o Most anterior is the forward extension

Function / Cavity/Takes Place -

Parathyroid Small diverticulum

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Fate

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Parathyroid arises from:

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Lateral recesses

cavity of pharynx

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Ultimobranchial body (rudimentary 5th pharyngeal pouch/lateral pouch) Arytenoid Swellings - Cause for U-shaped appearance of pharynx

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On ventral wall of 4th pharyngeal pouch

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Swellings from pharyngeal floor

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Between pair of arytenoid swellings Below glottis

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On top of ultimobranchial body Beside dorsal aorta’s outer periphery

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Glottis

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Larynx

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Dorsal Aorta Pair of big blood vessels Anterior Cardinal Vein - Big blood vessels Ventral Aorta - Bears arytenoid swellings

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Artery below larynx in mesenchymal mass

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- On sides of diencephalon

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Fate of Arytenoid swellings? Yoq na bes -

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Space or cavity Leads to larynx Cavity in mesenchymal mass -

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Eye -Studied at level of diencephalon A. OPTIC CUP -Rounded or elongated structure B. SENSORY RETINA - Inner thicker layer of optic

Small depression or cavity of epithelial lining

POSTERIORLY Connection of paired 3rd branchial arch, ventral aorta and dorsal aorta Thyroid Gland o Mass cells below ventral aorta o Found at start of union/connectio n

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(anteriorly) FORMED: - Paired branchial (aortic) arch meet to form ventral aorta - Thyroid Gland (DERIVED) - At level between 2nd pharyngeal epithelium and push into mesenchyme -

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Optic nerves

Dorsal wall of epithelium of 4th Pharyngeal Pouch

cup

C. PIGMENTED EPITHELIUM -Outer thinner layer of optic cup D. LENS VESICLE - Small sac – like structure within optic cup

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- Choroid fissure groove

- on ventral rim of optic cup

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- Optic Stalk Narrow space -

Corneal Epithelium

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Pharynx Smaller before Larynx

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emerge from inner retina converges at choroid fissure on its way to the brain What do you call the brownish pigment in it? Hay jusq di ko alam -

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How did it arise??? Invagination of Skin Ectoderm (pls confirm) -

area where portion of optic cup is missing (dorsal side) - Connecting optic cup and diencephalon - Skin ectoderm covering lens vesicle Level of the Pulmonary Aorta and Telencephalon

Location

Function / Cavity/Takes Place -

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- Small cavity below pharynx Paired 6th Aortic Arch - on mesenchymal mass below pharynx Pulmonary Trunk of Conus Arteriosus Bulbus Cordis - Chamber of heart

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Fate

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Unites to form arm of Y – shaped figure Lower portion of Y – shaped figure Where pulmonary trunk is extended ventrally Blood Flow

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Aortic Trunk Blood vessel Pericardial Cavity

Telencephalon Continuation of diencephalon

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- Beside pulmonary trunk -

Nasal Pit - On lateral surfaces of Pair of cavities head close to upper Olfactory Pit extends to portion of oral cavity telencephalon

Olfactory Nerves Streak of nerves Synonym: Olfactory

- Between nasal pit and anteroventral wall of telencephalon

Ventricle  Bulbus Cordis  Ventral Aorta  Aortic Arches - Embedded in bulbus cordis - Where bulbus cordis lies Telencephalic Vesicles - Lateral outgrowths - Ventricle I and III Interventricular Foramen - Means of ventricles to communicate Foramen of Monro - Communicate ventricle III of diencephalon with Telencephalic vesicles - Elevated regions of mesenchyme - Lateral and medial regions of mesenchyme if moved posteriorly Posterior Nares/ Nasal Choanae - opening of pit to oral cavity Nostrils/ External Nares external openings -

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What is the fate of the Lateral and Medial Nasal processes??? Who knows? We might never know

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PIT DEEPENING (ARISES) - Olfactory pit invagination and growth of nasal processes -

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Pit -

Name and Description

Esophagus Tiny, thick – walled circular hole Trachea - Thick – walled cavity Apical Bronchus Synonym: Eparterial Bronchus -

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Level of Heart and Apical Bronchus

Location

- Beneath paired dorsal aorta

Function / Cavity/Takes Place

- Beneath esophagus

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Marks union of anterior and posterior cardinal veins

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Where common cardinals open Valvulae Venosae guard the entrance into atria prevents backflow of blood from atria to sinus venosus

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Atrium thin walled portion of heart no signs of musculature

Took place of larynx -

Common Cardinal - Beside dorsal aorta Veins - Bigger pair of cardinal veins - Syonyms: Ducts of Cuvier Sinus Venosus - Thin walled chamber

Fate

Interatrial Septum - Marks right and left chambers Interatrial Foramen - Small opening between right and left chambers

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Fate? Feel ko lungs haha pls confirm -

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Fate of Openings of common cardinals: ATRIA

ARISES FROM Unapired evagination of trachea on right side -

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Fate of Sinus Venosus? IDK -

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Ventricle Thick walled chamber of heart

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Atrioventricular Canal (Left & Right) -Keeps atria and ventricles continuous

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Endocardial Cushion- In between left and right Mass of mesenchyme atrioventricular canals Pericardial Cavity Parietal Pericardium

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Trabeculae Carnae - Muscular ridges on ventricle Interventricular Septum - Dorsally incomplete - Presence of interventricular foramen -

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Wall of the Heart A. Endocardium - Close contact with blood - Inner layer of heart B. Myocardium - Middle and thickest layer of heart C. Epicardium Outer layer of outer lining of heart - Synonym: Visceral Pericardium

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Cavity enclosing heart Lining of Pericardial Cavity

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What valves will develop within the right atrioventricul ar canal? Left atrioventricul ar canal?

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Development of the Pig Embryo

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