17.6: Vidonda vya Adrenal
- Page ID
- 178307
Malengo ya kujifunza
- Eleza eneo na muundo wa tezi za adrenal
- Kutambua homoni zinazozalishwa na gamba adrenal na medulla adrenal, na muhtasari lengo seli zao na madhara
Vidonda vya adrenal ni wedges ya tishu za glandular na neuroendocrine zinazoambatana na juu ya figo na capsule ya nyuzi (Kielelezo\(\PageIndex{1}\)). Vidonda vya adrenal vina damu tajiri na hupata mojawapo ya viwango vya juu zaidi vya mtiririko wa damu katika mwili. Wao hutumiwa na mishipa kadhaa ya matawi ya aorta, ikiwa ni pamoja na mishipa ya suprarenal na ya figo. Damu inapita kwa kila tezi ya adrenal kwenye kamba ya adrenal na kisha huingia kwenye medulla ya adrenal. Homoni za adrenal hutolewa katika mzunguko kupitia mishipa ya kushoto na ya kulia ya suprarenal.
Gland ya adrenal ina kamba ya nje ya tishu za glandular na medulla ya ndani ya tishu za neva. Kamba yenyewe imegawanywa katika maeneo matatu: zona glomerulosa, zona fasciculata, na zona reticularis. Kila mkoa huficha seti yake ya homoni.
Adrenal gamba, kama sehemu ya hipothalami-pituitari adrenal (HPA) mhimili secretes homoni steroid muhimu kwa ajili ya udhibiti wa muda mrefu stress majibu, shinikizo la damu na kiasi cha damu, matumizi ya madini na kuhifadhi, maji na electrolyte usawa, kuvimba. Mhimili wa HPA unahusisha kusisimua kwa kutolewa kwa homoni ya homoni ya adrenokotikotropiki (ACTH) kutoka pituitari na hypothalamasi. ACTH kisha huchochea gamba la adrenali kuzalisha kotisoli ya homoni. Njia hii itajadiliwa kwa undani zaidi hapa chini.
Medulla ya adrenal ni tishu za neuroendocrine linajumuisha mfumo wa neva wa postganglionic wenye huruma (SNS) neurons. Ni kweli ugani wa mfumo wa neva wa uhuru, ambao unasimamia homeostasis katika mwili. Njia ya sympathomedullary (SAM) inahusisha kusisimua kwa medula kwa msukumo kutoka hypothalamus kupitia neurons kutoka kamba ya mgongo wa thoracic. Medulla huchochewa kutenganisha homoni za amine epinephrine na norepinephrine.
Moja ya kazi kubwa ya tezi ya adrenal ni kujibu matatizo. Stress inaweza kuwa ama kimwili au kisaikolojia au wote wawili. Mkazo wa kimwili ni pamoja na kufichua mwili kuumia, kutembea nje katika hali ya baridi na mvua bila kanzu juu, au utapiamlo. Mkazo wa kisaikolojia ni pamoja na mtazamo wa tishio la kimwili, kupigana na mpendwa, au siku mbaya tu shuleni.
Mwili hujibu kwa njia tofauti kwa dhiki ya muda mfupi na dhiki ya muda mrefu kufuatia mfano unaojulikana kama syndrome ya kukabiliana na hali ya jumla (GAS). Hatua moja ya GAS inaitwa mmenyuko wa kengele. Hii ni dhiki ya muda mfupi, majibu ya kupambana na ndege, yanayopatanishwa na homoni epinephrine na norepinephrine kutoka medula ya adrenal kupitia njia ya SAM. Kazi yao ni kuandaa mwili kwa nguvu kali ya kimwili. Mara baada ya shida hii imefunguliwa, mwili unarudi kwa kawaida. Sehemu ya medulla ya adrenal inashughulikia majibu haya kwa undani zaidi.
Ikiwa shida haijaondolewa hivi karibuni, mwili unafanana na shida katika hatua ya pili inayoitwa hatua ya upinzani. Ikiwa mtu ana njaa kwa mfano, mwili unaweza kutuma ishara kwa njia ya utumbo ili kuongeza ngozi ya virutubisho kutoka kwa chakula.
Ikiwa mkazo unaendelea kwa muda mrefu hata hivyo, mwili hujibu kwa dalili tofauti kabisa na majibu ya kupigana-au-ndege. Wakati wa hatua ya uchovu, watu wanaweza kuanza kuteseka unyogovu, ukandamizaji wa majibu yao ya kinga, uchovu mkali, au hata mashambulizi ya moyo. Dalili hizi hupatanishwa na homoni za gamba la adrenali, hasa kotisoli, iliyotolewa kutokana na ishara kutoka mhimili wa HPA.
Homoni za adrenali pia zina kazi kadhaa zisizo na dhiki zinazohusiana, ikiwa ni pamoja na ongezeko la viwango vya sodiamu na glucose za damu, ambazo zitaelezewa kwa undani hapa chini.
Adrenal gamba
Kamba ya adrenal ina tabaka nyingi za seli za kuhifadhi lipid zinazotokea katika mikoa mitatu ya kimuundo. Kila moja ya mikoa hii hutoa homoni tofauti.
Homoni za Zona Glomerulosa
Eneo la juu zaidi la gamba la adrenali ni glomerulosa ya zona, ambayo inazalisha kundi la homoni kwa pamoja linajulikana kama mineralocorticoids kwa sababu ya athari zao kwa madini ya mwili, hasa sodiamu na potasiamu. Homoni hizi ni muhimu kwa usawa wa maji na electrolyte.
Aldosterone ni mineralocorticoid kuu. Ni muhimu katika udhibiti wa mkusanyiko wa ioni za sodiamu na potasiamu katika mkojo, jasho, na mate. Kwa mfano, hutolewa kwa kukabiliana na damu iliyoinuliwa K +, damu ya chini Na +, shinikizo la damu, au kiasi cha chini cha damu. Kwa kukabiliana, aldosterone huongeza excretion ya K + na uhifadhi wa Na +, ambayo huongeza kiasi cha damu na shinikizo la damu. Usiri wake unasababishwa wakati CRH kutoka hypothalamus husababisha kutolewa kwa ACTH kutoka pituitary ya anterior.
Aldosteroni pia ni sehemu muhimu ya mfumo wa renini-angiotensin-aldosterone (RAAS) ambapo seli maalumu za figo hutoa renini ya enzyme kwa kukabiliana na kiasi cha chini cha damu au shinikizo la damu. Renin kisha kuchochea uongofu wa damu protini angiotensinogen zinazozalishwa na ini, kwa homoni angiotensin I. angiotensin I ni kubadilishwa katika mapafu angiotensin II angiotensin kuwabadili enzyme (ACE). Angiotensin II ina kazi tatu kuu:
- Kuanzisha vasoconstriction ya arterioles, kupungua kwa mtiririko wa damu
- Kuchochea tubules za figo kwa reabsorbing NaCl na maji, kuongeza kiasi cha damu
- Kuashiria kamba ya adrenal ili kuzuia aldosterone, madhara ambayo huchangia zaidi uhifadhi wa maji, kurejesha shinikizo la damu na kiasi cha damu
Kwa watu wenye shinikizo la damu, au shinikizo la damu, madawa ya kulevya yanapatikana ambayo huzuia uzalishaji wa angiotensin II. Dawa hizi, zinazojulikana kama ACE inhibitors, kuzuia enzyme ACE kubadilisha angiotensin I kwa angiotensin II, hivyo kupunguza uwezo wa mwisho wa kuongeza shinikizo la damu.
Homoni za Zona Fasciculata
Mkoa wa kati wa kamba ya adrenal ni zona fasciculata, inayoitwa kama vile kwa sababu seli huunda fascicles ndogo (vifungu) vinavyotengwa na mishipa ya damu ndogo. Seli za zona fasciculata huzalisha homoni zinazoitwa glucocorticoids kwa sababu ya jukumu lao katika kimetaboliki ya glucose. Jambo muhimu zaidi ni cortisol, ambayo baadhi ya ini hubadilika kuwa cortisone. Glucocorticoid zinazozalishwa kwa kiasi kidogo ni corticosterone. Kwa kukabiliana na matatizo ya muda mrefu, hypothalamus inaficha CRH, ambayo kwa hiyo husababisha kutolewa kwa ACTH na pituitary ya anterior. ACTH husababisha kutolewa kwa glucocorticoids. Athari yao ya jumla ni kuzuia ujenzi wa tishu huku wakisisimua kuvunjika kwa virutubisho vilivyohifadhiwa ili kudumisha vifaa vya kutosha vya mafuta. Katika hali ya dhiki ya muda mrefu, kwa mfano, cortisol inakuza catabolism ya glycogen kwa glucose, catabolism ya triglycerides kuhifadhiwa katika fatty kali na glycerol, na catabolism ya protini misuli katika amino asidi. Malighafi haya yanaweza kutumiwa kuunganisha glucose na ketoni za ziada kwa matumizi kama mafuta ya mwili. Hippocampus, ambayo ni sehemu ya lobe ya muda ya cortices ya ubongo na muhimu katika malezi ya kumbukumbu, ni nyeti sana kwa viwango vya dhiki kwa sababu ya receptors zake nyingi za glucocorticoid.
Pengine wewe ni ukoo na dawa ya dawa na yanayouzwa zenye glucocorticoids, kama vile sindano cortisone katika viungo inflamed, vidonge prednisone na inhalers steroid makao kutumika kusimamia pumu kali, na creams hydrocortisone kutumika ili kupunguza story vipele ngozi. Dawa hizi zinaonyesha jukumu lingine la kotisoli-downregulation ya mfumo wa kinga, ambayo huzuia majibu ya uchochezi.
Homoni za Reticularis ya Zona
Eneo la kina kabisa la kamba ya adrenal ni zona reticularis, ambayo hutoa kiasi kidogo cha darasa la homoni za ngono za steroid inayoitwa androgens. Wakati wa ujana na wengi wa watu wazima, androgens huzalishwa katika gonads. Androgens zinazozalishwa katika zona reticularis kuongeza androgens gonadal. Wao huzalishwa kwa kukabiliana na ACTH kutoka pituitary ya anterior na hubadilishwa katika tishu kwa testosterone au estrogens. Katika wanawake wazima, wanaweza kuchangia kwenye gari la ngono, lakini kazi yao kwa wanaume wazima haijulikani vizuri. Katika wanawake baada ya menopausal, kama kazi za ovari hupungua, chanzo kikuu cha estrogens inakuwa androgens zinazozalishwa na zona reticularis.
Adrenal Medulla
Kama ilivyoelezwa hapo awali, kamba ya adrenal hutoa glucocorticoids kwa kukabiliana na matatizo ya muda mrefu kama vile ugonjwa mkali. Kwa upande mwingine, medulla ya adrenal hutoa homoni zake kwa kukabiliana na shida kali, ya muda mfupi iliyopatanishwa na mfumo wa neva wenye huruma (SNS).
Tishu za medullari zinajumuisha neuroni za kipekee za SNS za postganglionic zinazoitwa chromaffin, ambazo ni kubwa na zisizo za kawaida, na kuzalisha nyurotransmita za epinephrine (pia huitwa adrenaline) na noradrenalini (au noradrenaline). Epinephrine huzalishwa kwa kiasi kikubwa-takriban uwiano wa 4 hadi 1 na norepinephrine-na ni homoni yenye nguvu zaidi. Kwa sababu seli za chromaffin hutoa epinephrine na norepinephrine katika mzunguko wa utaratibu, ambapo husafiri sana na huathiri seli za mbali, zinachukuliwa kuwa homoni. Inatokana na tyrosine ya amino asidi, huwekwa kikemia kama catecholamines.
Secretion ya medullary epinephrine na norepinephrine kudhibitiwa na njia ya neural inayotokana na hypothalamus katika kukabiliana na hatari au dhiki (SAM njia). Wote epinephrine na norepinephrine ishara ini na seli skeletal misuli kubadili glycogen katika glucose, kusababisha kuongezeka kwa viwango vya damu glucose. Homoni hizi huongeza kiwango cha moyo, pigo, na shinikizo la damu ili kuandaa mwili kupambana na tishio linalojulikana au kukimbia. Aidha, njia hupunguza hewa, kuongeza viwango vya oksijeni ya damu. Pia husababisha vasodilation, kuongeza zaidi oksijeni ya viungo muhimu kama vile mapafu, ubongo, moyo, na misuli ya mifupa. Wakati huo huo, husababisha vasoconstriction kwa mishipa ya damu inayohudumia viungo vya chini muhimu kama njia ya utumbo, figo, na ngozi, na hudhibiti baadhi ya vipengele vya mfumo wa kinga. Madhara mengine ni pamoja na mdomo kavu, kupoteza hamu ya kula, upanuzi wa mwanafunzi, na kupoteza maono ya pembeni. Homoni kuu za tezi za adrenal zinafupishwa katika Jedwali\(\PageIndex{1}\).
| Adrenal gland | Associated hormones | Chemical class | Effect |
|---|---|---|---|
| Adrenal cortex | Aldosterone | Steroid | Increases blood Na+ levels |
| Adrenal cortex | Cortisol, corticosterone, cortisone | Steroid | Increase blood glucose levels |
| Adrenal medulla | Epinephrine, norepinephrine | Amine | Stimulate fight-or-flight response |
Disorders Involving the Adrenal Glands
Several disorders are caused by the dysregulation of the hormones produced by the adrenal glands. For example, Cushing’s disease is a disorder characterized by high blood glucose levels and the accumulation of lipid deposits on the face and neck. It is caused by hypersecretion of cortisol. The most common source of Cushing’s disease is a pituitary tumor that secretes cortisol or ACTH in abnormally high amounts. Other common signs of Cushing’s disease include the development of a moon-shaped face, a buffalo hump on the back of the neck, rapid weight gain, and hair loss. Chronically elevated glucose levels are also associated with an elevated risk of developing type 2 diabetes. In addition to hyperglycemia, chronically elevated glucocorticoids compromise immunity, resistance to infection, and memory, and can result in rapid weight gain and hair loss.
In contrast, the hyposecretion of corticosteroids can result in Addison’s disease, a rare disorder that causes low blood glucose levels and low blood sodium levels. The signs and symptoms of Addison’s disease are vague and are typical of other disorders as well, making diagnosis difficult. They may include general weakness, abdominal pain, weight loss, nausea, vomiting, sweating, and cravings for salty food.
Chapter Review
The adrenal glands, located superior to each kidney, consist of two regions: the adrenal cortex and adrenal medulla. The adrenal cortex—the outer layer of the gland—produces mineralocorticoids, glucocorticoids, and androgens. The adrenal medulla at the core of the gland produces epinephrine and norepinephrine.
The adrenal glands mediate a short-term stress response and a long-term stress response. A perceived threat results in the secretion of epinephrine and norepinephrine from the adrenal medulla, which mediate the fight-or-flight response. The long-term stress response is mediated by the secretion of CRH from the hypothalamus, which triggers ACTH, which in turn stimulates the secretion of corticosteroids from the adrenal cortex. The mineralocorticoids, chiefly aldosterone, cause sodium and fluid retention, which increases blood volume and blood pressure.
Interactive Link Questions
Visit this link to view an animation describing the location and function of the adrenal glands. Which hormone produced by the adrenal glands is responsible for mobilization of energy stores?
Answer: Cortisol.
Review Questions
Q. The adrenal glands are attached superiorly to which organ?
A. thyroid
B. liver
C. kidneys
D. hypothalamus
Answer: C
Q. What secretory cell type is found in the adrenal medulla?
A. chromaffin cells
B. neuroglial cells
C. follicle cells
D. oxyphil cells
Answer: A
Q. Cushing’s disease is a disorder caused by ________.
A. abnormally low levels of cortisol
B. abnormally high levels of cortisol
C. abnormally low levels of aldosterone
D. abnormally high levels of aldosterone
Answer: B
Q. Which of the following responses s not part of the fight-or-flight response?
A. pupil dilation
B. increased oxygen supply to the lungs
C. suppressed digestion
D. reduced mental activity
Answer: D
Critical Thinking Questions
Q. What are the three regions of the adrenal cortex and what hormones do they produce?
A. The outer region is the zona glomerulosa, which produces mineralocorticoids such as aldosterone; the next region is the zona fasciculata, which produces glucocorticoids such as cortisol; the inner region is the zona reticularis, which produces androgens.
Q. If innervation to the adrenal medulla were disrupted, what would be the physiological outcome?
A. Damage to the innervation of the adrenal medulla would prevent the adrenal glands from responding to the hypothalamus during the fight-or-flight response. Therefore, the response would be reduced.
Q. Compare and contrast the short-term and long-term stress response.
A. The short-term stress response involves the hormones epinephrine and norepinephrine, which work to increase the oxygen supply to organs important for extreme muscular action such as the brain, lungs, and muscles. In the long-term stress response, the hormone cortisol is involved in catabolism of glycogen stores, proteins, and triglycerides, glucose and ketone synthesis, and downregulation of the immune system.
Glossary
- adrenal cortex
- outer region of the adrenal glands consisting of multiple layers of epithelial cells and capillary networks that produces mineralocorticoids and glucocorticoids
- adrenal glands
- endocrine glands located at the top of each kidney that are important for the regulation of the stress response, blood pressure and blood volume, water homeostasis, and electrolyte levels
- adrenal medulla
- inner layer of the adrenal glands that plays an important role in the stress response by producing epinephrine and norepinephrine
- angiotensin-converting enzyme
- the enzyme that converts angiotensin I to angiotensin II
- alarm reaction
- the short-term stress, or the fight-or-flight response, of stage one of the general adaptation syndrome mediated by the hormones epinephrine and norepinephrine
- aldosterone
- hormone produced and secreted by the adrenal cortex that stimulates sodium and fluid retention and increases blood volume and blood pressure
- chromaffin
- neuroendocrine cells of the adrenal medulla
- cortisol
- glucocorticoid important in gluconeogenesis, the catabolism of glycogen, and downregulation of the immune system
- epinephrine
- primary and most potent catecholamine hormone secreted by the adrenal medulla in response to short-term stress; also called adrenaline
- general adaptation syndrome (GAS)
- the human body’s three-stage response pattern to short- and long-term stress
- glucocorticoids
- hormones produced by the zona fasciculata of the adrenal cortex that influence glucose metabolism
- mineralocorticoids
- hormones produced by the zona glomerulosa cells of the adrenal cortex that influence fluid and electrolyte balance
- norepinephrine
- secondary catecholamine hormone secreted by the adrenal medulla in response to short-term stress; also called noradrenaline
- stage of exhaustion
- stage three of the general adaptation syndrome; the body’s long-term response to stress mediated by the hormones of the adrenal cortex
- stage of resistance
- stage two of the general adaptation syndrome; the body’s continued response to stress after stage one diminishes
- zona fasciculata
- intermediate region of the adrenal cortex that produce hormones called glucocorticoids
- zona glomerulosa
- most superficial region of the adrenal cortex, which produces the hormones collectively referred to as mineralocorticoids
- zona reticularis
- deepest region of the adrenal cortex, which produces the steroid sex hormones called androgens