Integumentary System
The integumentary system consists of skin and its appendages: sweat glands, nails, hairs, sebaceous glands, arrector muscles of hairs (arrector pili muscles), mammary glands, and teeth. Development of Skin and…
GENERAL
Common Signaling Pathways Used During Development
During the process of embryonic development, undifferentiated precursor cells differentiate and organize into the complex structures found in functional adult tissues. This intricate process requires cells to integrate many intrinsic…
Pharyngeal Apparatus, Face, and Neck
T he pharyngeal apparatus consists of pharyngeal arches, pouches, grooves, and membranes ( Fig. 9.1 ). These early embryonic structures contribute to the formation of the face and neck. Fig….
Development of Limbs
Early Stages of Limb Development 15 The upper limb buds are visible by day 24, and the lower limb buds appear 1 or 2 days later, with the activation of…
Alimentary System
T he alimentary system (digestive system) is the digestive tract from the mouth to the anus, with all its associated glands and organs. The primordial gut forms during the fourth…
Discussion of Clinically Oriented Problems
Chapter 1 1. The secondary sexual characteristics develop, reproductive functions begin, and sexual dimorphism becomes more obvious during puberty. The pubertal changes are not the same in males and females….
Skeletal System
As the notochord and neural tube form in the third week, the intraembryonic mesoderm lateral to these structures thickens to form two longitudinal columns of paraxial mesoderm ( Fig. 14.1…
Muscular System
The muscular system develops from mesoderm , except for the muscles of the iris of the eye, which develop from neuroectoderm (neural crest cells) , and the muscles of the…
Placenta and Fetal Membranes
The placenta and fetal membranes separate the fetus from the endometrium , the inner layer of the uterine wall. An interchange of substances, such as nutrients and oxygen, occurs between…
Body Cavities, Mesenteries, and Diaphragm
Early in the fourth week of development of the embryo, the intraembryonic coelom appears as a horseshoe-shaped cavity ( Fig. 8.1 A ). The bend in the cavity at the…
