By O. Malir. Medical College of Georgia. 2017.
In a typical reproductive cycle safe 2.5 mg prinivil, a woman ovulates 14 days prior to the onset of the next menstruation and is fertile for approxi- mately 20 to 24 hours following ovulation. Adding 9 months, or 38 weeks, to the time of ovulation gives one the estimated delivery date. Developmental © The McGraw−Hill Anatomy, Sixth Edition Development Anatomy, Postnatal Companies, 2001 Growth, and Inheritance Chapter 22 Developmental Anatomy, Postnatal Growth, and Inheritance 761 Digestive tract Amnion Amniotic fluid Skin Heart Spinal cord Chorion Body stalk with umbilical vessels Syncytiotrophoblasts Brain Yolk sac Endoderm Mesoderm Ectoderm Muscle: smooth, cardiac, and skeletal Connective tissue: embryonic, Epidermis of skin and epidermal connective tissue proper, derivatives: hair, nails, glands cartilage, bone, blood of the skin; linings of oral, nasal, Dermis of skin; dentin of teeth anal, and vaginal cavities Epithelium of blood vessels, Nervous tissue; sense organs lymphatic vessels, body Lens of eye; enamel of teeth cavities, joint cavities Pituitary gland Internal reproductive organs Adrenal medulla Kidneys and ureters Adrenal cortex Epithelium of pharynx, external acoustic canal, tonsils, thyroid, parathyroid, thymus, larynx, trachea, lungs, GI tract, urinary bladder and urethra, and vagina Liver and pancreas FIGURE 22. Developmental © The McGraw−Hill Anatomy, Sixth Edition Development Anatomy, Postnatal Companies, 2001 Growth, and Inheritance 762 Unit 7 Reproduction and Development bon dioxide can be removed; (2) establishment of a constant, Knowledge Check protective environment around the embryo that is conducive to 4. List the structural characteristics of a zygote, morula, and development; (3) establishment of a structural foundation for blastocyst. Approximately when do each of these stages of embryonic morphogenesis along a longitudinal axis; (4) provi- the preembryonic period of development occur? Discuss the process of implantation and describe the phys- through genetic expression. If these needs are not met, a sponta- iological events that ensure pregnancy. Serious developmental defects usually cause the embryo to be naturally aborted. About 25% of early aborted embryos EMBRYONIC PERIOD have chromosomal abnormalities. Other abortions may be caused by environmental factors, such as infectious agents or teratogenic The events of the 6-week embryonic period include the differentia- drugs (drugs that cause birth defects). In addition, an implanted em- tion of the germ layers into specific body organs and the formation bryo is regarded as foreign tissue by the immune system of the of the placenta, the umbilical cord, and the extraembryonic mem- mother, and is rejected and aborted unless maternal immune re- sponses are suppressed. Objective 7 Define embryo and describe the major events Extraembryonic Membranes of the embryonic period of development. At the same time that the internal organs of the embryo are Objective 8 List the embryonic needs that must be met to being formed, a complex system of extraembryonic membranes avoid a spontaneous abortion. The extraembryonic membranes are the amnion, yolk sac, allantois, and chorion.
Starting thyroid hormone therapy after behavioral deficits have occurred cannot reverse the mental retardation (i generic prinivil 10mg with visa. Thyroid hormone deficiency during infancy RNA polymerase II DNA causes both mental retardation and growth impairment, as discussed below. Fortunately, this occurs rarely today be- cause thyroid hormone deficiency is usually detected in newborn infants and hormone therapy is given at the TRE proper time. Corepressor The exact mechanism by which thyroid hormones influ- ence differentiation of the CNS is unknown. T4 is taken up by the cell and deiod- cell replication in the brain and stimulate the growth of inated to T3, which then binds to the thyroid hormone receptor nerve cell bodies, the branching of dendrites, and the rate (TR). The activated TR heterodimerizes with a second transcrip- tion factor, 9-cis retinoic acid receptor (RXR), and binds to the of myelinization of axons. The binding of mones are presumably due to their ability to regulate the TR/RXR to the TRE displaces repressors of transcription and re- expression of genes involved in nerve cell replication and cruits additional coactivators. However, the details, particularly in the hu- RNA polymerase II and the transcription of the target gene. CHAPTER 33 The Thyroid Gland 603 Thyroid Hormones Are Essential for involved; the amounts of oxygen consumed and body heat Normal Body Growth produced depend on total body activity. The thyroid hormones are important factors regulating the Thermogenic Action of the Thyroid Hormones. For example, an individual who hormones regulate the basal rate at which oxidative phos- is deficient in thyroid hormones, who does not receive thy- phorylation takes place in cells. As a result, they set the roid hormone therapy during childhood, will not grow to a basal rate of body heat production and of oxygen con- normal adult height. A major way Thyroid hormone levels in the blood must be within thyroid hormones promote normal body growth is by normal limits for basal metabolism to proceed at the rate stimulating the expression of the gene for growth hor- needed for a balanced energy economy of the body. For ex- mone (GH) in the somatotrophs of the anterior pituitary ample, if thyroid hormones are present in excess, oxidative gland. In a thyroid hormone-deficient individual, GH phosphorylation is accelerated, and body heat production synthesis by the somatotrophs is greatly reduced and con- and oxygen consumption are abnormally high.
The mechanism by which this takes Nucleolytic place is not well understood trusted 2.5 mg prinivil. Ribonuclease Cleaves ribonucleic acids into mononucleotides Deoxyribonuclease Cleaves deoxyribonucleic acids into mononucleotides BILIARY SECRETION The suffix -ogen or prefix pro- indicates the enzyme is secreted in an in- The human liver secretes 600 to 1,200 mL/day of bile into active form. For example, bile Potentiation, as previously described for gastric secre- salts play an important role in the intestinal absorption of tion, also exists in the pancreas. Bile salts are derived from cholesterol and, therefore, cretion is a result of the different receptors used for ACh, constitute a path for its excretion. Secretin binding triggers an increase in portant route for the excretion of bilirubin from the body. Bile flows through the canaliculi to the and the neuropeptides GRP and substance P bind to their bile ducts, which drain into the gallbladder. During the in- 2 respective receptors and trigger the release of Ca from terdigestive state, the sphincter of Oddi, which controls TABLE 27. Cholic acid is converted to deoxycholic patic Bile acid and chenodeoxycholic acid to lithocholic acid. Bile Plasma At a neutral pH, the bile acids are mostly ionized and are Concentration Concentration referred to as bile salts. Conjugated bile acids ionize more Constituent (mEq/L) (mEq/L) readily than the unconjugated bile acids and, thus, usually Na 140–170 145 exist as salts of various cations (e. This property of bile salts is HCO 15–60 24 3 important because they play an integral role in the intes- tinal absorption of lipid. Therefore, it is important that bile salts are absorbed by the small intestine only after all of the the opening of the duct that carries biliary and pancreatic lipid has been absorbed. The major lipids in bile are phospholipids and choles- Thus, most of the hepatic bile is stored in the gallbladder terol. After the ingestion of a meal, CCK is re- phosphatidylcholine (lecithin). The phospholipid and cho- leased into the blood, causing contraction of the gallblad- lesterol concentrations of hepatic bile are 0.
The food is utilized at the cellular level order prinivil 2.5 mg otc, where nutrients are required for chemical reac- tions involving synthesis of enzymes, cellular division and growth, repair, and the production of heat energy. Most of the food we eat, however, is not suitable for cellular utilization until it is mechanically and chemically reduced to forms that can be absorbed through the intestinal wall and transported to the cells by the blood. Ingested food is not technically inside the body until it is absorbed; and, in fact, a large portion of this food re- mains undigested and passes through the body as waste material. The principal function of the digestive system is to prepare food for cellular utilization. This involves the following func- tional activities: • Ingestion—the taking of food into the mouth • Mastication—chewing movements to pulverize food and mix it with saliva • Deglutition—the swallowing of food to move it from the mouth to the pharynx and into the esophagus • Digestion—the mechanical and chemical breakdown of food material to prepare it for absorption • Absorption—the passage of molecules of food through the mucous membrane of the small intestine and into the FIGURE 18. It traverses the thoracic cavity and Anatomically and functionally, the digestive system can be enters the abdominal cavity at the level of the diaphragm. The GI tract, which ynx, esophagus, stomach, small intestine, and large intestine (fig. The accessory digestive organs include the teeth, tongue, salivary glands, liver, gallbladder, and pancreas. The term viscera is frequently used to refer to the abdominal organs ingestion: L. Digestive System © The McGraw−Hill Anatomy, Sixth Edition Body Companies, 2001 636 Unit 6 Maintenance of the Body TABLE 18. Specialized serous mem- with saliva (mastication); initiates digestion of branes support the GI tract and provide a structure through which carbohydrates; forms and swallows soft mass of nerves and vessels pass. The wall of the GI tract is composed of chewed food called bolus (deglutition) four tunics. Pharynx Receives bolus from oral cavity; autonomically continues deglutition of bolus to esophagus Objective 4 Describe the arrangement of the serous Esophagus Transports bolus to stomach by peristalsis; lower membranes within the abdominal cavity. These organs are supported and covered by down chyme; absorbs nutrients; transports wastes serous membranes that line the cavities of the trunk and cover through peristalsis to large intestine; prohibits the organs within these cavities.