Intermediate Mesoderm È Genital Ridge È Testes/Ovaries

GENITAL SYSTEM

Intermediate Mesoderm  Genital Ridge  Testes/Ovaries

Development of Testes Mesothelial Cells  Primary Sex Cords  Seminiferous Tubules  Network of Cords  Rete Testis

Intermediate Mesoderm  Leydig Cells  Secretes Testosterone Yolk Sac Mesoderm  Primordial Germ Cells  Spermatogonia Coelomic Mesothelium  Sertoli Cells (Supportive)  Secretes MIF

Male Genital Tract Mesonephric/Wolfian Ducts  Epididymis  Ductus Deferens (Vas Deferens)  Ejaculatory Duct

Development of Ovaries Primary Sex Cords  Rete Ovary (disappears) Secondary Sex Cords  From Primordial Follicles Yolk Sac Endoderm  Primordial Germ Cells  Oogonia Surface Mesothelium  Follicular Cells No oogonia Formed AFTER Birth

Female Genital Tract Mullerian Ducts Caudal Part  Uterovaginal Canal  Epithelium for Uterus, Cervix, Vagina Lower Part  Mesenchyme  Broad Ligament

Splanchnic Mesoderm  Endometrial Stroma and Myometrium

Sinus Tubercle  Sinovaginal Bulbs  Vaginal Plate Central Part  Vaginal Lumen Lower Part  Hymen (sep. lumen from UG Sinus)

Development of External Genitalia General Info Undifferentiated until 7th week Fully differentiated by 12th week Genital Tubercle  Rupture  UG orifice w/ UG folds (lat.) and Labioscrotal swellings (more lat.)

Male External Genitalia Genital Tubercle  Penis Labioscrotal  Scrotal Sac

Female External Genitalia Genital Tubercle  Clitoris UG Folds  Labia Minora  Frenulum UG Sinus  Vestibule of Vagina Labioscrotal  Labia Majora

Descent of Testes Gubernaculum  Epididymalscrotal swelling Associated with inguinal canal Contraction causes descent of testes

Descent of Ovaries Gubernaculum  Round Ligament AND Ovarian Ligament Contraction of gubernaculums pulls ovary down to pelvis Obstructed by uterus and broad ligament MUSCULOSKELETAL SYSTEM

Ossification of Long Bones ALL by endochondral EXCEPT clavicle Primary Centers before birth Secondary Centers after birth EXCEPTION: Lower Femur and Upper Tibia (Knee area) (before birth) Law of Ossification Secondary Centers appear FIRST and fuses LAST EXCEPTION: Fibula (secondary appears first and fuses first) Axial Skeleton Skull Suture joint where two flat bones meet Fontanelle where more than two bones meet ANTERIOR FONTANELLE CLOSES LAST (18-24 months after birth)

Intramembranous Top of Head and FACE Endochondral Oss. Everything Else (Back of Head, Ear Bones)

Vertebrae and Ribs Sclerotomes (somites; paraxial mesoderm) Notochord  Nucleus Pulposus

Development of Limbs Upper Limbs Buds Appear First Limb Buds Somatopleuric Mesoderm  Central Core of Mesoderm Apical Ectodermal Ridge  Induces/Controls Differentiation of Mesoderm into Bones and Muscles Somatopleuric Mesoderm  Muscles of Limbs Myotomes (Paraxial Mes.)  Muscles of Pelvis/Pectoral Girdles Hand/Foot Plate (6th week) Digital Rays  Rays Break to From Digits (8th week) Upper Limbs Rotate 90 (deg) LATERALLY Lower Limbs Rotate 90 (deg) MEDIALLY

Muscular System ALL Muscles from Mesoderm EXCEPTION: Constrictor/Dilator Pupillae (Neuroectoderm) Neural Crest Cells  Mesoderm of Head A) Striated Muscle 1. Somites (Myotomes) Epaxial  Extensors of Neck/Vertebral Column Hypaxial  Flexors of Trunk 2. Somatopleuric  Extensors/Flexors of Limbs 3. Occipital Somites  Tongue Muscles 4. Pre-Otic Somites  Ocular Muscles 5. Branchial Arch Mesoderm  See Charts

B) Splanchnopleuric Mesoderm  Smooth and Cardiac Muscles C) Somatic Mesoderm  Lymphatic & Blood Vessel PHARYNX

Derivatives of Pharyngeal Arches Skeletal Derivatives First Arch (Meckel’s Cartilage) Dorsal End  Malleus, Incus Dorsal Sheath  Anterior Ligament of Malleus Ventral Sheath  Body of Mandible Intermediate Sheath  Sphenomandibular Ligament Maxillary Process  Face and Secondary Palate

Second Arch (Rechert’s Cartilage) Dorsal end  Stapes, Styloid Process Ventral end  Upper Half of Body of Hyoid Lesser Cornu/Horn of Hyoid Intermediate Sheath  Stylohyoid Ligament

Third Arch Ventral end  Lower Half of Body of Hyoid Greater Horns of Hyoid

Arch IV & VI Ventral end  Fuse  Cartilage of Larynx

Endodermal Derivatives First Pouch Distal end  Lining of Tympanic Cavity and Antrum Proximal end  Lining of Pharyngotympanic Tube

Second Pouch Mesoderm  Palatine Tonsils Endoderm  Tonsilar Pits and Crypts REMNANT  Intratonsilar cleft

Third Pouch Dorsal Endoderm  Parathyroid III  INFERIOR Thyroid Ventral Endoderm  Thymus (inc. Epitihelial Reticula, Hassal’s Corpuscles)

Fourth Pouch Dorsal Endoderm  Parathyroid IV  SUPERIOR Thyroid Ventral Endoderm  Ultimobranchial Body  Parafollicular Cells (C Cells)

Pharyngeal Clefts 1st Cleft  External Auditory Meatus Tympanic Membrane  Endoderm, Ectoderm, AND Mesoderm

Cleft II-VI  Side of Neck Cervical Sinus  Should close

Development of Tongue Buccopharangeal Membrane ruptures on 26th day Lateral Lingual Swellings  Anterior 2/3 of mucus membrane of Tongue Tuberculum Impar  Doesn’t become anything Copula  Doesn’t become anything Hypobranchial Eminence Cranial  Posterior 1/3 of mucus membrane of Tongue Caudal  Epiglottis

Circumvallate Papillae Innervated by ARCH III

Development of Thyroid Endodermal Diverticulum  Thyroglossal Duct  Foramen Cecum Develops 7th week, Starts Secreting 12th Week

Salivary Glands Ectoderm  Parotid Gland Endoderm  Submandibular Gland Sublingual Gland FACE, PALATE, NOSE, TEETH

Development of Face

Mandibular Prominence  Lower Jaw Lower Lip Chin Lower Cheek

Maxillary Prominence  Upper Lip Zygomatics Maxillae (EXCEPT for Pre-Maxillary Part Secondary Palate SUPERFICIAL Filtrum of Lip

Medial Nasal Prominences  (Fuse  Intermaxillary Segment) DEEP Part of Filtrum Premaxillary Part of Filtrum Primary Palate

Lateral Nasal Prominences  Sides of Nose  + Maxillary  Nasolacrimal Duct

Frontonasal Prominence  Forehead  Dorsum/Apex of Nose

Development of Palate

Primary Palate  Median Palatal Process  Premaxillary Part of Hard Palate  Holds Incisors

Secondary Palate  Lateral Palatal Process  ALL Soft Palate (6th Arch Muscles)  Most Hard Palate

Junction of Primary/Secondary  Incisive Fossa

Development of Teeth Bud Stage 10 Tooth Buds Grow from Dental Lamina Cap Stage Stellate Reticulum Cap  Enamel Organ Bell Stage Dental Cap Becomes Bell Shaped

Dental Papillae  Dental Pulp Dental Sac  Cementum (inner) & Periodontal Ligament (Outer) Odontoblasts  Dentine Ameloblasts  Enamel

Tooth Eruption Occurs 6-24 months AFTER birth Permanent Teeth start around 6th year after birth

Nasal Cavities Before Birth Maxillary Sinus Ethmoid Sinus After Birth Frontal Sinus Sphenoid Sinus