assignment 14

assignment 14 - Sametra Williams Enrollment #: 646028...

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Sametra Williams Enrollment #: 646028 Assignment 14 January 1, 2009 1. Identify the hormones responsible: a. Initiation of lactation and maintenance of milk secretions: Prolactin. b. Growth and development of the ducts system: Estrogen. c. Full growth of the alveolar tissues: Progesterone. 2. The udder of the cow is divided into two halves; the right and left halves are separated by intramammary groove, the main support of the udder. The sides of the udder are covered by the lateral suspensory ligaments, which attach to the pelvic bone. The median and lateral ligaments come together at the bottom of the udder and form a sling in which the secretory tissue is held. The udder consists of four functional glands, each found in separate quarters. The rear quarters generally are larger than the forequarters and produce approx 60% of the milk. Inside each quarter are milk secreting cells called alveoli, which are microscopic in size and spherical in shape. Several alveoli make up a lobule, and several lobules make up a lobe. Milk produced in these alveoli empty into systems of ducts and into the gland and teat cisterns. The gland cistern is a small reservoir of milk (there is no movement of milk from one quarter to the other). Milk is produced in the epithelial cells surrounding each alveolus. Most of the milk is stored in the lumen of the alveolus. The sphincter muscle at the bottom of the teats keeps the milk from leaking out. The mammary gland may be compared to a bunch of grapes. 3. Epithelial cells are milk secreting cells surrounding each alveolus. Myoepithelial cells are smooth muscles which surrounds the alveoli. 4. The two important processes involved in the secretion of milk by the mammary gland are as follows: the first process is filtration of certain milk constituents directly from the blood stream into the milk; such as: immunoglobulins found in colostrum, water (which makes up 87% of milk), vitamins, and minerals. The second process is synthesis by cellular metabolism within the epithelial cells of each alveolus; the 6 nutrients in the blood passes through the cell walls to be used for synthesis of milk constituents not present in the blood. 5. Milk secretion: a. Milk secretion is fastest soon after milking and slowest as the next milking period approaches because of the pressure gradient that is present; reaches its max rate just after milking. b. If someone forgets to milk a cow, the pressure gradient will increase and if the pressure is not reduced through milking, milk secretion will cease and milk constituents undergo reabsorption into the bloodstream. c.
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This note was uploaded on 02/03/2009 for the course DARY 1048 taught by Professor Jenny during the Spring '08 term at LSU.

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assignment 14 - Sametra Williams Enrollment #: 646028...

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