Before We Are Born

1 - Introduction to Human Development

Importance of and Advances in Embryology

Descriptive Terms

Clinically Oriented Questions

2 - Human Reproduction

Reproductive Organs

Female Reproductive Organs

Male Reproductive Organs

Gametogenesis

Meiosis

Spermatogenesis

Oogenesis

Comparison of Male and Female Gametes

Female Reproductive Cycles

Ovarian Cycle

Menstrual Cycle

Transportation of Gametes

Oocyte Transport

Sperm Transport

Maturation of Sperms

Viability of Oocytes and Sperms

Clinically Oriented Questions

3 - First Week of Human Development

Fertilization

Phases of Fertilization

Results of Fertilization

Cleavage of Zygote

Formation of Blastocyst

Clinically Oriented Questions

4 - Second Week of Human Development

Formation of Amniotic Cavity, Embryonic Disc, and Umbilical Vesicle

Development of Chorionic Sac

Implantation Sites of Blastocytes

Clinically Oriented Questions

5 - Third Week of Human Development

Gastrulation: Formation of Germ Layers

Primitive Streak

Notochordal Process and Notochord

Neurulation: Formation of the Neural Tube

Neural Plate and Neural Tube

Neural Crest Formation

Development of Somites

Development of Intraembryonic Coelom

Early Development of Cardiovascular System

Vasculogenesis and Angiogenesis

Development of Chorionic Villi

Clinically Oriented Questions

6 - Fourth to Eighth Weeks of Human Development

Folding of Embryo

Head and Tail Folds

Lateral Folds

Germ Layer Derivatives

Control of Embryonic Development

Estimation of Embryonic Age

Highlights of the Fourth to Eighth Weeks

Fourth Week

Fifth Week

Sixth Week

Seventh Week

Eighth Week

Clinically Oriented Questions

7 - Fetal Period: The Ninth Week to Birth

Highlights of Fetal Period

Nine to Twelve Weeks

Thirteen to Sixteen Weeks

Seventeen to Twenty Weeks

Twenty-One to Twenty-Five Weeks

Twenty-Six to Twenty-Nine Weeks

Thirty to Thirty-Eight Weeks

Expected Date of Delivery

Factors Influencing Fetal Growth

Procedures for Assessing Fetal Status

Ultrasonography

Diagnostic Amniocentesis

Chorionic Villus Sampling

Cell Cultures

Percutaneous Umbilical Cord Blood Sampling

Magnetic Resonance Imaging

Fetal Monitoring

Alpha-Fetoprotein Assay

Noninvasive Prenatal Diagnosis

Neonatal Period

Clinically Oriented Questions

8 - Placenta and Fetal Membranes

Placenta

Decidua

Development of Placenta

Fetomaternal Junction

Intervillous Space

Amniochorionic Membrane

Placental Circulation

Parturition

Stages of Labor

Placenta and Fetal membranes after Birth

Umbilical Cord

Amnion and Amniotic Fluid

Significance of Amniotic Fluid

Umbilical Vesicle

Significance of Umbilical Vesicle

Allantois

Multiple Pregnancies

Twins and Fetal Membranes

Other Types of Multiple Births

Clinically Oriented Questions

9 - Body Cavities, Mesenteries, and Diaphragm

Embryonic Body Cavity

Mesenteries

Division of Embryonic Body Cavity

Development of Diaphragm

Septum Transversum

Pleuroperitoneal Membranes

Dorsal Mesentery of Esophagus

Muscular Ingrowth from Lateral Body Walls

Positional Changes and Innervation of the Diaphragm

Clinically Oriented Questions

10 - Pharyngeal Apparatus, Face, and Neck

Pharyngeal Arches

Pharyngeal Arch Components

Pharyngeal Pouches

Derivatives of Pharyngeal Pouches

Pharyngeal Grooves

Pharyngeal Membranes

Development of Thyroid Gland

Development of Tongue

Lingual Papillae and Taste Buds

Nerve Supply of Tongue

Development of Salivary Glands

Development of Face

Development of Nasal Cavities

Paranasal Sinuses

Development of Palate

Primary Palate

Secondary Palate

Clinically Oriented Questions

11 - Respiratory System

Development of Larynx

Development of Trachea

Development of Bronchi and Lungs

Maturation of Lungs

Clinically Oriented Questions

12 - Alimentary System

Foregut

Development of Esophagus

Development of Stomach

Development of Duodenum

Development of Liver and Biliary Apparatus

Development of Pancreas

Development of Spleen

Midgut

Rotation of Midgut Loop

Cecum and Appendix

Hindgut

Cloaca

Anal Canal

Clinically Oriented Questions

13 - Urogenital System

Development of Urinary System

Development of Kidneys and Ureters

Positional Changes of Kidneys

Changes in Blood Supply of Kidneys

Development of Urinary Bladder

Development of Urethra

Development of Suprarenal Glands

Development of Genital System

Development of Gonads

Development of Genital Ducts

Development of External Genitalia

Development of Inguinal Canals

Relocation of Testes and Ovaries

Descent of Testes

Descent of Ovaries

Clinically Oriented Questions

14 - Cardiovascular System

Early Development of Heart and Blood Vessels

Development of Veins Associated with Embryonic Heart

Pharyngeal Arch Arteries and Other Branches of the Dorsal Aorta

Fate of Vitelline and Umbilical Arteries

Later Development of Heart

Circulation through Primordial Heart

Partitioning of Primordial Heart

Changes in Sinus Venosus

Primordial Pulmonary Vein and Formation of Left Atrium

Partitioning of Primordial Ventricle

Partitioning of Bulbus Cordis and Truncus Arteriosus

Development of Cardiac Valves

Conducting System of Heart

Birth Defects of Heart and Great Vessels

Derivatives of Pharyngeal Arch Arteries

Derivatives of First Pair of Pharyngeal Arch Arteries

Derivatives of Second Pair of Pharyngeal Arch Arteries

Derivatives of Third Pair of Pharyngeal Arch Arteries

Derivatives of Fourth Pair of Pharyngeal Arch Arteries

Fate of Fifth Pair of Pharyngeal Arch Arteries

Derivatives of Sixth Pair of Pharyngeal Arch Arteries

Pharyngeal Arch Arterial Birth Defects

Fetal and Neonatal Circulation

Fetal Circulation

Transitional Neonatal Circulation

Derivatives of Fetal Vessels and Structures

Development of the Lymphatic System

Development of Lymph Nodes

Development of Spleen and Tonsils

Clinically Oriented Questions

15 - Musculoskeletal System

Skeletal System

Development of Cartilage and Bone

Histogenesis of Cartilage

Histogenesis of Bone

Development of Joints

Fibrous Joints

Cartilaginous Joints

Synovial Joints

Development of Axial Skeleton

Development of Vertebral Column

Cartilaginous Stage of Vertebral Development

Bony Stage of Vertebral Development

Development of Ribs

Development of Sternum

Development of Cranium

Development of Appendicular Skeleton

Muscular System

Development of Skeletal Muscle

Development of Smooth Muscle

Development of Cardiac Muscle

Development of Limbs

Early Stages of Limb Development

Final Stages of Limb Development

Cutaneous Innervation of Limbs

Blood Supply of Limbs

Clinically Oriented Questions

16 - Nervous System

Development of Nervous System

Development of Spinal Cord

Development of Spinal Ganglia

Development of Spinal Meninges

Positional Changes of Spinal Cord

Myelination of Nerve Fibers

Birth Defects of Spinal Cord

Development of Brain

Brain Flexures

Hindbrain

Myelencephalon

Metencephalon

Choroid Plexuses and Cerebrospinal Fluid

Midbrain

Forebrain

Congenital Anomalies of Brain

Development of Peripheral Nervous System

Spinal Nerves

Cranial Nerves

Development of Autonomic Nervous System

Sympathetic Nervous System

Parasympathetic Nervous System

Clinically Oriented Questions

17 - Development of Eyes and Ears

Development of Eyes and Related Structures

Development of Retina

Development of Choroid and Sclera

Development of Ciliary Body

Development of Iris

Development of Lens

Development of Aqueous Chambers

Development of Cornea

Development of Eyelids

Development of Lacrimal Glands

Development of Ears

Development of Internal Ears

Development of Middle Ears

Development of External Ears

Clinically Oriented Questions

18 - Integumentary System

Development of Skin and Appendages

Epidermis

Dermis

Development of Glands

Development of Hairs

Development of Nails

Development of Mammary Glands

Development of Teeth

Bud Stage of Tooth Development

Cap Stage of Tooth Development

Bell Stage of Tooth Development

Tooth Eruption

Clinically Oriented Questions

19 - Human Birth Defects

Teratology: Study of Abnormal Development

Birth Defects Caused by Genetic Factors

Numerical Chromosomal Abnormalities

Structural Chromosomal Abnormalities

Birth Defects Caused by Mutant Genes

Birth Defects Caused by Environmental Factors

Principles of Teratogenesis

Human Teratogens

Environmental Chemicals as Teratogens

Infectious Agents as Teratogens

Radiation as a Teratogen

Maternal Factors as Teratogens

Mechanical Factors as Teratogens

Birth Defects Caused by Multifactorial Inheritance

Clinically Oriented Questions

20 - The Cellular and Molecular Basis of Development

Intercellular Communication

Gap Junctions

Cell Adhesion Molecules

Morphogens

Retinoic Acid

Transforming Growth Factor-ß/Bone Morphogenetic Protein

Sonic Hedgehog

Wnt/ß-Catenin Pathway

Receptor Tyrosine Kinases

Common Features

Regulation of Angiogenesis by Receptor Tyrosine Kinases

Notch-Delta Pathway

Transcription Factors

Hox/Homeobox Proteins

Pax Genes

Basic Helix-Loop-Helix Transcription Factors

Epigenetics

DNA Methylation

Histone Modifications

Stem Cells: Differentiation versus Pluripotency

Summary of Common Signaling Pathways Used during Development

Bibliography and Suggested Reading

Answers to Clinically Oriented Questions

Index