endocrine portion of the pancreas consists of cellsarranged in groups, called “islands (islets) ofLangerhans.” The islands (islets) of Langerhanscontain three types of endocrine cells: alpha, beta, anddelta. The alpha cells secrete the hormone glucagon.Glucagon causes a temporary rise in blood sugarlevels. The beta cells secrete insulin, which is essentialfor carbohydrate metabolism. Insulin lowers bloodsugar levels by increasing tissue utilization of glucoseand stimulating the formation and storage of glycogenin the liver. Together, glucagon and insulin act toregulate sugar metabolism in the body. Delta cellsproduce the hormone somatostatin. Somatostatinhelps regulate carbohydrates by inhibiting thesecretion of glucagon.When the islet cells are destroyed or stopfunctioning, the sugar absorbed from the intestineremains in the blood and excess sugar is excreted bythe kidneys into the urine. This condition is calleddiabetes mellitus, or sugar diabetes. Insulin, asynthetic hormone, is given to patients having thisdisease as part of their ongoing treatment.GONADS (TESTES AND OVARIES)The term gonads refers to the primary sex organsof the reproductive system (male and female).TestesThe male gonad is the testis (pl. testes), and theexistence of the testes is the primary male sexcharacteristic (fig. 1-47). The testes produce andsecrete the male hormone testosterone, whichinfluences the development and maintenance of themale accessory sex organs and the secondary sexcharacteristics of the male. The male accessory sexorgans include two groups of organs: the internal sexorgans and the external sex organs. See section titled“Male Reproductive System” for more information onthe male accessory sex organs.Male Secondary Sex CharacteristicsMale secondary sex characteristics influenced bythe hormone testosterone are as follows:Increased growth of hair, particularly in the areasof the face, chest, axilla, and pubic region.Enlargement of the larynx (Adam's apple) andthickening of the vocal cords, which produces alower-pitched voice.Thickening of the skin.Increased muscle growth, broadening of theshoulder and narrowing of the waist.Thickening and strengthening of the bones.OvariesThe female gonads, the ovaries, produce thehormones estrogen and progesterone (fig. 1-47).E s t r o g e n i n f l u e n c e s t h e d e v e l o p m e n t a n dmaintenance of the female accessory sex organsa n d t h e s e c o n d a r y s e x c h a r a c t e r i s t i c s , a n dpromotes changes in the mucous lining of the uterus( e n d o m e t r i u m ) d u r i n g t h e m e n s t r u a l c y c l e .Progesterone prepares the uterus for the receptionand development of the fertilized ovum andmaintains the lining during pregnancy.Today, progesterone and estrogen hormones(naturally derived) are incorporated into oralcontraceptives or birth control pills. The combinationof hormones released through this monthly series ofpills fools the body into not preparing (building-up ofuterine lining) for implantation of an embryo. Becausethe uterus has not prepared for implantation,pregnancy cannot occur.Female accessory sex organs are also divided intointernal and external accessory sex organs. See sectiontitled “Female Reproductive System” for moreinformation on the female accessory sex organs.Female Secondary Sex CharacteristicsFemale secondary sex characteristics influencedby the hormone estrogen are listed below.Development of the breasts and the ductilesystem of the mammary glands within thebreasts.Increased quantities of fatty (or adipose) tissuein the subcutaneous layer, especially in thebreasts, thighs, and buttocks.Increased vascularization of the skin.1-44
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business