Adrenal Gland Histology Lecture (Dr. Cole) Flashcards
1
Q
Anatomy
A
- Suprarenal Glands, also known as Adrenal Glands
- A pair of Triangular-Shaped Glands, each about 2 Inches long and 1 inch wide
- SUPERIOR to the Kidneys
- HIGHLY VASCULARIZES
A) Superior Suprarenal: Inferior Phrenic
B) Middle Suprerena;: Abdominal Aorta
C) Inferior Suprarenal: Renal Artery
2
Q
Development of the Adrenal Glands Introduction
A
- Two parts of the Adrenal Glands, the CORTEX and the MEDULLA develop from Two Different Origins:
1) CORTEX:
- is MESODEMAL in Origin
- Develops from the CELOMIC EPITHELIUM of the POSTERIOR ABDOMINAL WALL
2) MEDULLA:
- Is ECTODERMAL in Origin
- Develops from the NEURAL CREST Cells
3
Q
Development of the Adrenal Glands Description
A
- By the EIGTH Week of Fetal Development, these Cortical Elements have differentiated into a THIN OUTER DEFINITIVE Cortex and a THICK INNER FETAL Cortex
- The FETAL Cortex actively produces FETAL STEROIDS during GESTATION, but INVOLUTES Rapidly after birth
- ADRENOCORTICAL rests occur in up to 50% of Newborn Infants, but tend to ATROPHY and DISAPPEAR in the Early POSTPARTUM Period. They can be detected anywhere along the Path of EMBRYONIC Migration of Adrenal Cortex
- ACCESSORY ADRENOCORTICAL NODULES (Ex: Ectopic Adrenal Gland, Accessory Cortical Tissue, Hamartoma, Asseccsory Adrenal Gland, Supernumerary Adrenal, and Adrenocortical Rest), accessory Adrenocortical Nodules are MINOR Developmental anomalies arising from Partly or Completely detached rests of the COELOMIC Epithelial Primordial form which the ADRENAL CORTEX IS DERIVED
- Thye are most frequently located in Contact with he Capsule at ONE POLE of the Adrenal but can occur COMPLETELY SEPARATED form the Adrenal Gland in the RETROPERITONEAL FAT
4
Q
Development of Adrenal Glands Description Cont 1
A
- The Development of ADRENAL ZONES occurs SLOWLY after Birth in Parallel with REGRESSION of the Fetal Cortex, and is not Completed until late in the FIRST YEAR of LIFE
- The DEFINITIVE CORTEX persists and develops into the FUNCTIONAL ADRENAL CORTEX, with Distinct ZONAE GLOMERULOSA and FASCICULATA present at BIRTH. The ZONA RETICULARIS develops during the FIRST YEAR of LIFE
- Both CORTICAL and MEDULLARY elements appear between the FIFTH and SIXTH Weeks of FETAL GROWTH
5
Q
Development of Adrenal Glands Description Cont 2
A
- The Adrenal MEDULLA and Sympathetic Nervous System develop in Concert
- The Medullary Elements, derived form NERUAL CREST, Migrate Forward to the PARA-AORTIC and PARAVERTEBRAL Regions and along the ADRENAL VEIN toward the MEDIAL aspect of the Developing ADRENAL FETAL CORTEX
6
Q
Explain the Function of the Fetal Adrenal Cortex. What are the Three Main Developmental Events that require Glucocorticoids?
A
- During the EARLY STAGE of Gestation, the Adrenal Cortex synthesizes DEHYDROEPIANDROSTERONE (DHEA), a precursor of the Synthesis of Estrogen by the PLACENTA
- A lack of 3 Beta-Hydroxysteroid Dehydrogenase (3Beta- HSD) activity prevents the SYNTHESIS of PROGESTERONE, GLUCOCORTICOIDS, and ANDROSTENEDIONE
- The interaction between the FETAL ADRENAL CORTEX and the Placenta is known as the FETOPLACENTAL UNIT
- 3Beta-Hydroxysteroid Dehydrogeanse II DEFICIENT CONGENITAL ADRENAL HYPERPLASIA ( 3Beta- HSD- CAH) is an Uncommon form of CONGENITAL ADRENAL HYPERPLASIA (CAH)
- Results from a Mutation in the Gene for (3Beta- HSD) TYPE II
- There is Wide Spectrum of Clinical Presentations of 3Beta- HSD CAH, from MILD to SEVERE forms
- MILDER forms resulting from INCOMPLETE LOSS of 3Beta- HSD Type II Function can produce VIRILIZATION of Genetically FEMALE Infants and UNDERVIRILIZATION of Genetically MALE Infants
- This form of PRIMARY HYPOADRENALISM is the ONLY form of CAH that can cause AMBIGIOUS GENITALIA in BOTH GENETIC SEXES!!!!!!!!!!!!
7
Q
The Main Developmental Events that Require Glucocorticoids
A
- Glucocorticoids, either of MATERNAL Origin or Synthesized from PLACENTAL PROGESTERONE by the Fetus, are essential for THREE Main Developmental Events:
1) The Production of SURFACTANT by TYPE II ALVEOLAR Cells after the EIGTH MONTH of Fetal Life
2) The Development of a FUNCTIONAL HYPOTHALAMOPITUITARY AXIS
3) The INDUCTION of THYMIC INVOLUTION
8
Q
Organization of the Adrenal Cortex
A
- Each Gland consists of Yellowish OUTER CORTEX (80 to 90% of the Gland) and a Reddish INNER MEDULLA (10 to 20%)
- The Adrenal Cortex is of MESODERMAL Origin and produces STEROID HORMONES
- The Adrenal Medulla is of NEUROECTODERMIC Origin and produces CATECHOLAMINES
- The Adrenal Cortex consists of three Concentric Zones:
1) OUTERMOST layer of the Cortex is the ZONA GLOMERULOSA
2) The MIDDLE Layer of the Cortex is the ZONA FASCICULATE
3) The INNERMOST layer of the Cortex is the ZONA RETICULARIS
9
Q
Zone Glomerulosa Products
A
- Mineralocorticoids, mainly ALDOSTERONE
- Produced in response to ANGIOTENSIN II (Also ACTH)
10
Q
Zona Glomerulosa Description
A
- Liws under the Capsule and represents 10 to 15% of the Cotex
- Cells aggregate into a GLOMERULUS-like arrangement and have a Moderate amount of LIPID DROPLETS in the Cytoplasm
- Lacks the Enzyme 17 ALPHA- HYDROXYLASE (CYP17), CANNOT produce CORTISOL or SEX STEROIDS
- ALDOSTERONE stimulates the RETENTION of Na+ in the Kidneys, the RETENTION of Water (AS a consequence of Na+ Reabsorption), and RENAL SECRETION of K+ and H+
11
Q
Zona Fasciculata
A
- 75% of the CORTEX!!!!!
- Secretes GLUCOCORTICOIDS and ANDROGENS
- Cells contain MANY Lipid Droplets of CHOLESTEROL (Precursor in Cytoplasm)
- Cells appear VACUOLATED (Foamy appearance)
- **** SPONGIOCYTES!!!!!!!!!!!!!
12
Q
Zona Fasciculata Contents
A
- Contains CUBOID CELLS, with the structural features of Steroid-producing Cells arranged in LONGITUDINAL CORDS separated by Cortical Fenestrated Capillaries/ Sinusoids!!
13
Q
ZF and ZR
A
- Contain 17ALPHA- HYDROXYLASE necessary for the Production of GLUCOCORTICOIDS—- CORTISOL—- and the Enzyme 17, 20- HYDROXYLASE, required for the production of SEX HORMONES!!!!!!
- CORTISOL is not stored in Cells and New Synthesis, stimulated by ACTH, is required for achieving a Hormonal Increase in BLOOD CIRCULATION
- CORTISOL is converted in HEPATOCYTES to CORTISONE
- Synthetically made CORTISONE is used as an ANTI-INFLAMMATORY and ANTI-ALLERGY Agent
14
Q
Zona Fasciculata Effects
A
Has two major Effects:
1) A METABOLIC Effect: Stimulates GLUCONEOGENESIS to INCREASE the concentration of GLUCOSE in Blood
2) An ANTI-INFLAMMATORY Effect: SUPPRESSES tissues RESPONSES to Injury and DECREASES Cellular and Humoral Immunity
15
Q
Zona Fasciculate and Reticularis difference
A
- Although ZONA FASCICULATE is often associated with GLUCOCORTICOID Production- mainly CORTISOL - and the ZONA RETICULARIS with ANDROGEN Production, the Functional distinctions are NOT precise and they appear as a Functional Unit
- BOTH LAYERS are stimulated by CORTICOTROPIN (ACTH)
