* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download the exterior, nervous, urinary, and endocrine systems of domestic
Survey
Document related concepts
Blood–brain barrier wikipedia , lookup
Proprioception wikipedia , lookup
Human brain wikipedia , lookup
History of neuroimaging wikipedia , lookup
Neural engineering wikipedia , lookup
Causes of transsexuality wikipedia , lookup
Cognitive neuroscience wikipedia , lookup
Selfish brain theory wikipedia , lookup
Embodied cognitive science wikipedia , lookup
Neuropsychopharmacology wikipedia , lookup
Metastability in the brain wikipedia , lookup
Haemodynamic response wikipedia , lookup
Neuropsychology wikipedia , lookup
Microneurography wikipedia , lookup
Neuroregeneration wikipedia , lookup
Stimulus (physiology) wikipedia , lookup
Transcript
ANIMAL SCIENCE 8646-F THE EXTERIOR, NERVOUS, URINARY, AND ENDOCRINE SYSTEMS OF DOMESTIC ANIMALS INTRODUCTION An agricultural producer should be knowledgeable of the anatomy and physiology of livestock. A background of anatomical and physiological features of animals assists the producer in evaluating, selecting, breeding, and managing the herd. This topic includes a discussion of the nervous, urinary, and endocrine systems, as well as the external anatomy of animals. NERVOUS SYSTEM An animal’s nervous system consists of two major parts - the central nervous system and peripheral nervous system. The brain and spinal cord make up the central nervous system. The somatic nerves* and autonomic nerves make up the peripheral nervous system. One function of the nervous system is to organize the physical movement of the body. Another function is to respond to the actions of all the senses. The nervous system allows the animal to react to internal or external stimuli in the environment. Each nerve cell (neuron) consists of an individual, long fiber (axon) and several branched threads (dendrites). Other nerves and receptor organs (such as a sense organ) stimulate the dendrites. An impulse then passes through the dendrites to the axon. The point at which a dendrite connects to an axon is a synapse. The impulse may be sent to another dendrite or to an effector organ (for example, a muscle cell). Before an impulse can reach the brain or go from the brain to an effector organ, it must pass through a number of neurons and synapses. Not all impulses go to the brain. Some are sent directly to the effector organ. Nerves occur as single neurons or in bundles (nerve trunks). Fat-containing sheaths cover some nerve fibers. Ganglions consist of nerve trunks. They are outside of the brain and spinal cord. Sensory neurons are nerve cells that get stimuli and carry them to the central nervous system. Motor neurons are nerve cells that carry messages from the brain to muscles or glands. * Underlined words are defined in the Glossary of Terms. -1- The cerebrum, cerebellum, pons, and medulla oblongata are the major parts of the brain. The largest part is the cerebrum. It is large relative to body size in the more intelligent animals. The cerebrum consists of many folds and appears wrinkled. It is in charge of the thinking process that makes the decisions for voluntary muscle activities. The cerebrum is also responsible for reacting to sense stimuli. If the cerebrum should become damaged, not all body functions cease. The cerebellum coordinates messages from other parts of the brain for transmission to the body. It controls muscles performing normal activities (walking, running, eating, etc.). If the cerebellum should become damaged, incoordination may result, but not paralysis. The pons and medulla oblongata control reflex actions such as eye blinking, vomiting, breathing, and swallowing. The pons and medulla usually act independently of the cerebrum and cerebellum. The spinal cord is the main avenue for message transferals between the brain and other parts of the body. Located in the center of the vertebral column, the spinal cord is divided into parts or segments. A pair of spinal nerves extends to the body from each part of the spinal cord. The spinal cord receives messages from the nerve fibers from various body parts and transmits those messages to the brain. Motor nerve fibers in the spinal cord then transmit the responses from the brain back to the body parts. Somatic nerves control the functions of the body tissues other than the main body organs. All nerve structures located outside of the brain and spinal cord make up the peripheral nervous system. Somatic nerves are a part of that system and transmit messages between the outer parts of the body and the brain. Autonomic nerves, also a part of the peripheral nervous system, control the functions of involuntary muscles in the internal organs (such as the heart and stomach). Autonomic nerves provide almost automatic regulation of involuntary functions. These nerves transmit messages between the brain and the involuntary muscles. -2- EXTERNAL ANATOMY (Note: The selection and evaluation series of topics provide more in-depth explanations of the external body parts of animals.) Skin is the external covering of the animal’s body. It is continuous with the outer layers of the respiratory, reproductive, and digestive tracts. Hair, wool, horns, feathers, toenails, and hooves are modified extensions of the skin. Cattle, goats, sheep, and hogs have cloven or split hooves, while horses do not. The functions of skin are to protect against disease and infection and to regulate body temperature. Skin contains glands for secretion and excretion and sensory nerves to help the animal react to its environment. The skin of animals consists of two layers - epidermis and dermis. The epidermis is the outer layer of the skin and contains no blood cells. The dermis is the inner layer of the skin. It contains blood vessels, lymph vessels, nerves, glands, hair follicles, and muscle fibers. The primary glands of the skin are sweat glands and sebaceous glands. Sebaceous glands secrete oily substances to lubricate the skin and hair. The dermis may also contain special types of glands, such as the sweat glands found in the snout of a hog and mammary glands found in all mammals. Thickness of skin varies with animal species, breed, sex, and body location. The coat covering of cattle, goats, horses, and hogs is hair; for sheep, it is wool. In temperate, or cold climates, the hair coat of animals grows long for protection and is shed when the climate becomes warmer. The wool of sheep is shorn in the spring and provides a product of economic value. The mohair of goats is shorn in the early spring and late summer, also providing a valuable economic product. Feathers, the body covering of poultry, are molted in the late summer. New feathers grow before winter to protect the fowl. Hair, wool, and feathers are all composed of protein and produced by gene action. -3- URINARY SYSTEM The parts of the urinary system include the kidneys, ureters, bladder, and urethra. The kidneys, located in the abdominal cavity just under the lumbar vertebrae, are closely attached to the abdominal wall. In cattle and poultry, the kidneys consist of various lobes or parts. In horses, the right kidney is heart-shaped while the left kidney is bean-shaped. In sheep and hogs, the kidneys are both bean-shaped. Each kidney consists of an outer tissue layer (renal cortex) and an inner portion (renal medulla). The medulla contains many blood vessels and urinary tubules. The renal artery conveys blood to the kidneys. Blood filters from the capillaries into the blind sac of the urinary tubules. The urinary tubules network together and form larger tubules toward the center of the kidney where urine-containing body wastes are collected. One of the main functions of the kidneys is to filter waste products from the blood. Some of the waste products include mineral salts and various wastes from protein metabolism, such as urea, uric acid, and creatinine. The kidneys also regulate blood composition and maintain normal internal life support conditions. An animal cannot survive if both kidneys fail to function. The ureters are tubules that connect the kidneys with the bladder. They transport urine from the kidneys to the bladder. The bladder, an expandable sac, stores the urine until it is expelled from the animal’s body. Urine passes from the bladder through an elastic tubule (urethra) to be voided from the body. The urethra is in the penis in males and is connected to the vagina in females. In poultry, there is no bladder and the urine is transported by the ureters to the cloaca, where it is excreted with feces. No liquid urine is excreted by poultry. The white material in the droppings of poultry is uric acid, the urinary excretion of poultry. In other domestic animals, urinary waste is excreted in the form of urinary nitrogen. ENDOCRINE SYSTEM The proper functioning of the many cells and organs that comprise an animal’s body is largely dependent upon the action and interaction of chemical substances secreted by endocrine glands. Endocrine glands are usually small and located in various body parts. They secrete hormones. Because endocrine glands are ductless, they secrete the hormones directly into the bloodstream. Conversely, exocrine glands release their secretions into ducts that lead to the body surface or into cavities within the body. The pancreas is both an exocrine gland (secretes pancreatic juices into the small intestine) and an endocrine gland (secretes insulin into the bloodstream). Small amounts of hormones are excreted into the bloodstream but have powerful effects on the body. For example, 1/1,000,000 (one millionth) gram of oxytocin will cause immediate letdown of milk in lactating females. -4- After being secreted into the bloodstream, hormones travel to different body parts where they stimulate certain organs to perform specific functions. Some body functions in which hormones play an important role include growth and fattening, reproduction, lactation, and egg laying. The efficiency and performance of animals depend on the proper level and chemical balance of the hormones in performing specific functions. The pituitary gland, also known as the “master gland” of the body, is composed of two parts - anterior pituitary gland and posterior pituitary gland. The pituitary gland is located in a bony depression at the base of the brain. The anterior pituitary gland is cherry-shaped with its stem attached to the brain. It directly and indirectly controls the hormonal secretions of various endocrine glands. If the pituitary is removed or becomes dysfunctional, the adrenal cortex, gonads (ovaries or testicles), and the thyroid gland do not secrete the hormones for which they are responsible. This results in arrested growth, inactivity of the gonads and accessory sex organs, suppression of lactation, and atrophy of the thyroid, adrenal cortex, and parathyroids. Other hormonal malfunctions include increased sensitivity to insulin, a lowered metabolic rate, and less resistance to infection and shock. The hypothalamus is located directly above the pituitary gland. It is a small area of the brain that coordinates hormonal activity by regulating the release of hormones from the anterior pituitary gland and producing hormones that are stored and released from the posterior pituitary gland. Stimulating or inhibiting hormones produced by the hypothalamus are transported to the anterior pituitary by means of portal blood vessels. The hormones oxytocin and vasopressin produced in the hypothalamus travel to the posterior pituitary by means of nerve cells. -5- The thyroid gland consists of two connected lobes located on either side of the trachea or windpipe. The production of the hormone thyroxine by the thyroid gland is stimulated by thyrotropic hormones produced by the anterior pituitary gland. Thyroxine controls body metabolism and growth by increasing energy production and oxygen consumption by most body tissues. Calcitonin, a hormone also produced by the thyroid, controls the calcium level in the blood and promotes incorporation of calcium into bone. The parathyroid glands include four small glands adjacent to or embedded in the thyroid gland. They produce parathyroid hormones that maintain or increase the level of calcium and phosphorus in the blood. The adrenal glands, consisting of a medulla and cortex, are located in front of the center of the kidneys. The medulla produces the hormone adrenaline (epinephrine) that stimulates the heart and controls its rate and strength of contraction. The medulla also produces nonepinephrine, which helps maintain blood pressure and stimulates smooth muscles. The cortex produces steroids, some of which are involved in protein, carbohydrate, and fat metabolism. Androgens and estrogens produced by the gonads (ovaries and testicles) and the anatomy and physiology of the reproductive system are discussed in detail in a separate topic on animal reproduction. Hormones are produced and required in very small amounts to perform their specific functions. Hormones affect the growth of animals, shape of the animals’ bodies, feed efficiency, and adaptation of animals to the environment. Some specific hormones act on different tissues in different species. Hormones may be quickly deactivated and disappear from the bloodstream within a few hours, but their effects may not become apparent until a few hours or days after being administered. After they are in the bloodstream, hormones do not reach target organs merely by accident. They are attracted by receptors within the cells of tissues for which they are intended and bind with specific substances. After the hormone interacts with the receptor, the desired response or action is initiated. The production of hormones by endocrine glands is carefully balanced, and an imbalance can result in illness or improper development of the animal. The interaction of various hormones or the actual level of the specific hormone in the bloodstream may control this delicate balance. Acknowledgements Kristy Corley, Graduate Technician, Department of Agricultural Education, Texas A&M University, revised this topic. Larry Ermis, Curriculum Specialist, Instructional Materials Service, Texas A&M University, reviewed this topic. Vickie Marriott, Office Software Associate, Instructional Materials Service, Texas A&M University, prepared the layout and design of this topic. Christine Stetter, Artist, Instructional Materials Service, Texas A&M University, prepared the illustrations for this topic. -6- REFERENCES Bogart, Ralph and Robert E. Taylor. Scientific Farm Animal Production. Minneapolis, MN: Burgess Publishing Company, 2000. Campbell, John R. and John F. Lasley. The Science of Animals That Serve Humanity. St. Louis, MO: McGraw Hill Book Company, 2001. Endocrine System. [On-line]. Available: http://encarta.msn.com/find/search.asp?search=endocrine. [2002, March]. Frandson, R. D. Anatomy and Physiology of Animals. Philadelphia, PA: Lea & Fibiger, 1992. Nervous System. [On-line]. Available: http://encarta.msn.com/find/search.asp?search=nervous. [2002, March]. Organization of the Nervous System. [On-line]. Available: http://www.ultranet.com/ ~jkimball/BiologyPages/P/PNS.html. [2002, March]. Pathophysiology of Endocrine System. [On-line]. Available: http://arbl.cvmbs.colostate.edu/ hbooks/pathphys/endocrine/index.html. [2002, March]. Urinary System. [On-line]. Available: http://encarta.msn.com/find/search.asp?search=urinary. [2002, March]. GLOSSARY OF TERMS Autonomic nerves – Nerves that regulate involuntary action, as of the intestines, heart, and glands. Creatinine – A creatine anhydride, C4H7 N3 O, formed by the metabolism of creatine and found in muscle tissue and blood and normally excreted in the urine as a metabolic waste. Effector organ – An organ or tissue that effects or causes a reaction in animals in response to a stimuli. Gene – The smallest unit of inheritance; genes occur in pairs on chromosomes in the nucleus of a cell. Hormones – Chemical substances produced in the body by endocrine glands and transported by the blood to other organs to stimulate their functions. Somatic nerves – Nerves that control voluntary movements in the body, such as those performed by the skeletal muscles. SELECTED STUDENT ACTIVITIES SHORT ANSWER/LISTING: Answer the following questions or statements in the space provided or on additional paper. 1. Why is basic knowledge of animal anatomy and physiology important to an agricultural producer? ____________________________________________________________________________ ____________________________________________________________________________ 2. Name the two major parts of the nervous system and briefly list the components of each. a. _________________________________________________________________________ b. _________________________________________________________________________ 3. Name the four major parts of the brain. a. _______________________________ b. _______________________________ -7- c. d. _______________________________ _______________________________ 4. What is the difference between somatic nerves and autonomic nerves? ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ 5. Differentiate between the epidermis and dermis of skin. ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ 6. Name and briefly list a function of each of the four parts of the urinary system. a. _________________________________________________________________________ b. _________________________________________________________________________ c. _________________________________________________________________________ d. _________________________________________________________________________ 7. How is urine expelled from a chicken’s body? ____________________________________________________________________________ 8. What is the purpose of the endocrine glands? ____________________________________________________________________________ 9. Where is the pituitary gland located? ____________________________________________________________________________ 10. How do hormones reach their intended targets? ____________________________________________________________________________ ADVANCED ACTIVITIES 1. Research the endocrine system in other available information resources for an animal species (for example, search the Internet for “endocrine system AND sheep”). Then, in your own words, explain the endocrine system’s function for the animal species. Explain the relationship between the endocrine system and other body organ systems of the animal species. 2. Leather is made from the hides of animals. Research and report on the processes involved in making leather. ALL RIGHTS RESERVED Reproduction prohibited without written permission. Instructional Materials Service Texas A&M University 2588 TAMUS College Station, Texas 77843-2588 http://www-ims.tamu.edu 2002 -8-