EMBRYONIC DEVELOPMENT & STEM CELL COMPENDIUM
EMBRYONIC DEVELOPMENT & STEM CELL COMPENDIUM
13. Implantation and Its Preparation: General Concepts
Review of MEDICAL EMBRYOLOGY Book by BEN PANSKY, Ph.D, M.D.
- Changes in the uterine mucosa
- IMPLANTATION generally takes place on the 21st day of the menstrual cycle during the progestational phase
- At this time, the mucosa is thick, highly vascularized, and contains a large amount of glyogen
- There are proliferation and predominance of secretion, congestion, and edema of the uterine wall
- The blastocyst finds conditions in-the uterus very favorable for its implantation, especially for its nutrition
- Hormonal aspects of implantation
- ACTION OF OVARIAN HORMONES ON THE ENDOMETRIUM
- During each menstrual cycle, the uterine mucosa undergoes preparation for implantation which is directly conditioned by the ovarian hormones estrogen and progesterone
- The theca interna of the graafian follicle is the major source of estrogen, and the corpus luteum of pregnancy is the principal source of progesterone
- Morphologic changes in the uterine mucosa during the menstrual cycle result in proliferation of the endometrium involving not only the epithelium, the glands, and the stroma, but also, in a very essential way, the blood vessels
- Hypophyseal-ovarian relationship
- HYPOPHYSIS: endocrine activity of the ovary is under the control of the anterior lobe of the pituitary gland. The latter, in the human, secretes 2 gonad-stimulating hormones called gonadotropins or gonadotropes
- Follicle-stimulating hormone (FSH) is secreted from the very beginning of the menstrual cycle and determines the growth of the ovarian follicle
- Luteinizing hormone (LH) is secreted in the middle of the cycle and acts synergistically with FSH to provoke ovulation. LH stimulates the development of the corpus luteum
- THE OVARY: the endocrine activity of the ovary, under the influence of the hypophyseal gonadotropins, is diphasic
- During phase 1, it secretes estrogen
- During phase 2, both estrogen and progesterone are secreted
- The secretion of progesterone is detectable even before the formation of the corpus luteum
