Lab 13: Endocrine system & Digestive system
When you are prepared for the Test on Week 13 Learning Objectives in Week 14, you will be able to:
- Identify endocrine glands and describe their basic functions.
- Identify major structures and organs of the digestive system and their functions.
- Identify structures of teeth and classify teeth as incisors, canines, premolars, and molars.
- Identify absorptive structures of the small intestine.
- Identify mesentery structures and peritoneal attachments of abdominal organs.
- Describe the pathway that food takes through the primary organs of the digestive system.
- Describe the pathways of bile and pancreatic enzymes to the small intestine.
The Endocrine System
Communication is a process in which a sender transmits signals to one or more receivers to control and coordinate actions. In the human body, two major organ systems participate in relatively “long distance” communication: the nervous system and the endocrine system. Together, these two systems are primarily responsible for maintaining homeostasis in the body.
The nervous system uses two types of intercellular communication, electrical signaling (action potentials) and chemical signaling (neurotransmitters) that results in rapid signaling through the body. The target cell of the nervous system responds within milliseconds of receiving the chemical “message”; this response then ceases very quickly once the neural signaling ends. In this way, neural communication enables body functions that involve quick, brief actions, such as movement, sensation, and cognition. In contrast, the endocrine system uses just one method of communication: chemical signaling. These signals are sent by the endocrine organs, which secrete chemicals—the hormone—into the extracellular fluid. Hormones are transported primarily via the bloodstream throughout the body, where they bind to receptors on target cells, inducing a characteristic response. As a result, endocrine signaling requires more time than neural signaling to prompt a response in target cells, though the precise amount of time varies with different hormones. For example, the hormones released when you are confronted with a dangerous or frightening situation, called the fight-or-flight response, occur by the release of adrenal hormones—epinephrine and norepinephrine—within seconds. In contrast, it may take up to 48 hours for target cells to respond to certain reproductive hormones.
Although a given hormone may travel throughout the body in the bloodstream, it will affect the activity only of its target cells; that is, cells with receptors for that particular hormone. Once the hormone binds to the receptor, a chain of events is initiated that leads to the target cell’s response. Hormones play a critical role in the regulation of physiological processes because of the target cell responses they regulate. These responses contribute to human reproduction, growth and development of body tissues, metabolism, fluid, an