Anatomy and Physiology of Children and Adolescents - M. R. Sapin 2007

Endocrine System
Classification, Structure, and Functions of Endocrine Glands
Adrenal Glands

The Adrenal gland, or suprarenal gland, consists of two distinct glands that differ in origin, Structure, and function. The peripheral layers form the adrenal cortex, while the inner portion comprises the medulla. The adrenal gland is situated above the upper pole of the Kidney. The mass of a single adrenal gland in an adult human is 12–15 g. The gland is enclosed in a Connective Tissue capsule, from which thin septa extend into the interior of the organ. These septa divide the cortex into numerous epithelial cords enmeshed in a dense network of Blood capillaries.

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Fig. 1. Cleavage of the zygote and formation of germ layers: A — Fertilization: 1 - spermatozoon; 2 - ovum; B; C - zygote cleavage; D - moruloblastula: 1 - embryoblast; 2 - trophoblast; E - blastocyst: 1 - embryoblast; 2 - trophoblast; 3 — amniotic cavity; F - blastocyst: 1 - embryoblast; 2 - amniotic cavity; 3 — blastocoele; 4 — embryonic endoderm; 5 — amniotic epithelium; G — I: 1 — ectoderm; 2 — endoderm; 3 — mesoderm

Fig. 3. Cross-section through the embryo body (diagram): 1 — neural tube; 2 — notochord; 3 — aorta; 4 — sclerotome; 5 — myotome; 6 — dermatome; 7 — primitive gut; 8 — body cavity (coelom); 9 — somatopleure; 10 — splanchnopleure

Fig. 6. STRUCTURE OF THE cytolemma: 1 — Lipids; 2 — hydrophobic zone of lipid molecules; 3 — protein molecules; 4 — Polysaccharides of the glycocalyx

Fig. 13. Nerve Cells: 1 — nerve endings; 2 - dendrites; 3 - neurite (axon); 4 — nerve Cell body

Fig. 16. Structure of an osteon: 1 — osteonic canal; 2 — concentric bone lamellae; 3 — bone cells (osteocytes)

Fig. 71. Structure of the Placenta: 1 — umbilical artery; 2 — umbilical vein; 3 — umbilical cord; 4 — amniotic epithelium; 5 — chorionic plate; 6 — subchorionic space; 7 — cell island; 8 — basal trophoblast; 9 — spiral Arteries; 10 — decidual Veins; 11 — intervillous space; 12 — fibrin strips; 13 — anchoring villi; 14 — placental septa; 15 — myometrium; 16 — decidua; 17 — tubular fibrin; 18 — marginal sinus

Fig. 73. Structure of a lymphoid nodule in the wall of the Small Intestine: 1 — lymphoid nodule; 2 — germinal center of the lymphoid nodule; 3 — muscularis mucosae; 4 — intestinal mucosa; 5 — intestinal villi

Fig. 74. Arrangement of lymphoid structures in the Spleen: 1 — fibrous capsule; 2 — trabecula; 3 — venous sinuses; 4 — macrophage-lymphoid sheath (ellipsoid); 5 — penicillar arterioles; 6 — central artery; 7 — lymphoid nodule; 8 — periarterial lymphoid sheath; 9 — red pulp; 10 — pulp artery; 11 — splenic vein; 12 — splenic artery; 13 — trabecular artery and vein

Fig. 76. Structure of The Lymphatic system: 1 — facial Lymphatic vessels; 2 — submandibular Lymph Nodes; 3 — lateral cervical lymph nodes; 4 — left jugular trunk; 5 — left subclavian trunk; 6 — Thoracic duct; 7 — parasternal nodes; 8 — axillary lymph nodes; 9 — intestinal trunk; 10 — superficial lymphatic Vessels of the upper limb; 11 — common and external iliac lymph nodes; 12 — superficial inguinal lymph nodes; 13 — superficial lymphatic vessels of the lower limb; 14 — right lumbar trunk

Fig. 80. Circulatory system (general diagram): 1 — left common carotid artery; 2 — left Internal jugular vein; 3 — aortic arch; 4 — left Subclavian Artery and vein; 5 — left pulmonary artery; 6 — pulmonary trunk; 7 — left Pulmonary veins; 8 — Heart; 9 — descending part of the aorta; 10 — brachial artery; 11 — gastric artery; 12 — INFERIOR VENA CAVA; 13 — common left iliac artery and vein; 14 — femoral artery; 15 — popliteal artery; 16 — posterior tibial artery; 17 — anterior tibial artery; 18 — arteries and VEINS OF THE dorsum of the FOOT; 19 — arteries and veins of the leg; 20 — femoral vein; 21 — right internal iliac artery and vein; 22 — right external iliac artery and vein; 23 — superficial palmar arterial arch; 24 — radial artery and vein; 25 — ulnar artery and vein; 26 — portal vein; 27 — brachial artery and vein; 28 — axillary artery and vein; 29 — SUPERIOR VENA CAVA; 30 — right brachiocephalic vein; 31 — brachiocephalic trunk; 32 — left brachiocephalic vein

Fig. 85. Heart. Anterior view: 1 — pulmonary trunk; 2 — left auricle; 3 — anterior interventricular branch of the left coronary artery; 4 — great cardiac vein; 5 — left ventricle; 6 — right ventricle; 7 — right coronary artery; 8 — right auricle; 9 — aortic arch; 10 — superior vena cava

Fig. 88. Systemic (greater) and pulmonary (lesser) circuits of Blood Circulation: 1 — heart; 2 — aorta; 3 — celiac trunk; 4 — gastric vessels; 5 — splenic vessels; 6 — mesenteric artery; 7 — vessels of the small and large intestines; 8 — vessels of the trunk and lower limbs; 9 — inferior vena cava; 10 — portal vein; 11 — hepatic vessels; 12 — hepatic vein; 13 — pulmonary trunk; 14 — superior vena cava; 15 — pulmonary veins; 16 — pulmonary vessels; 17 — vessels of the HEAD and Neck

Fig. 89. Arteries of the Brain. Arterial circle of the brain. Inferior view: 1 — anterior communicating artery; 2 — anterior cerebral artery; 3 — Internal Carotid Artery; 4 — middle cerebral artery; 5 — posterior communicating artery; 6 — posterior cerebral artery; 7 — Basilar artery; 8 — vertebral artery; 9 — posterior inferior cerebellar artery; 10 — anterior inferior cerebellar artery; 11 — superior cerebellar artery

Fig. 90. Arteries of the upper limb. Anterior view: 1 — brachial artery; 2 — profunda brachii artery; 3 — subscapular artery; 4 — anterior humeral circumflex artery; 5 — axillary artery; 6 — subclavian artery; 7 — common carotid artery; 8 — brachiocephalic trunk; 9 — superior ulnar collateral artery; 10 — inferior ulnar collateral artery; 11 — ulnar artery; 12 — interosseous artery; 13 — radial artery; 14 — deep palmar arch; 15 — superficial palmar arch; 16 — common palmar digital arteries; 17 — proper palmar digital arteries

Fig. 93. Arteries of the lower limb. Anterior view: 1 — external iliac artery; 2 — common iliac artery; 3 — internal iliac artery; 4 — obturator artery; 5 — femoral circumflex artery; 6 — profunda femoris artery; 7 — femoral artery; 8 — descending genicular artery; 9 — medial superior genicular artery; 10 — popliteal artery; 11 — posterior tibial artery; 12 — fibular artery; 13 — dorsalis pedis artery; 14 — arcuate artery; 15 — medial plantar artery; 16 — plantar arch; 17 — lateral plantar artery; 18 — anterior tibial artery; 19 — lateral inferior genicular artery

Fig. 94. Superficial veins of The Human Body: 1 — superficial temporal vein; 2 — facial vein; 3 — External Jugular Vein; 4 — Anterior jugular vein; 5 — cephalic vein; 6 — superficial palmar venous arch; 7 — basilic vein; 8 — median cubital vein; 9 — superficial epigastric vein; 10 — great saphenous vein; 11 — dorsal venous arch of the foot; 12 — superficial dorsal venous network of the hand

Fig. 103. Cortical center of general sensitivity. The diagram shows the projection of human body parts onto the region of the cortical end of the general sensitivity analyzer (postcentral gyrus). Schematic coronal section of the cerebral hemisphere: 1 — postcentral gyrus; 2 — temporal lobe of the brain; 3 — lateral sulcus; 4 — lateral ventricle; 5 — longitudinal cerebral fissure

Fig. 104. Cortical center of the motor analyzer. The diagram shows the projection of human body parts onto the region of energy/motor analyzer's cortical end (precentral gyrus). Schematic coronal section of the cerebral hemisphere: 1 — precentral gyrus; 2 — temporal lobe of the brain; 3 — lateral sulcus; 4 — lateral ventricle; 5 — longitudinal cerebral fissure

The cortical substance is divided into three zones: the zona glomerulosa (outer), zona fasciculata (middle), and zona reticularis (bordering the medulla). The zona glomerulosa is formed by small cells arranged in rounded clusters (glomeruli). The zona fasciculata forms the widest part of the cortex; its large cells are arranged in long cords oriented perpendicularly to The surface of the organ. In the narrow zona reticularis, cells form small clusters (cell groups). The cells of these zones secrete various Hormones. Mineralocorticoids (aldosterone) are produced in the zona glomerulosa, glucocorticoids (hydrocortisone, cortisone, and corticosterone) in the zona fasciculata, and androgens, estrogens, and progesterone in the zona reticularis.

The adrenal medulla is formed by clusters of large cells (chromaffin cells) separated by sinusoidal capillaries. Two Types of cells are distinguished: epinephrocytes, which produce adrenaline, and norepinephrine-secreting cells (norepinephrocytes).

Adrenal hormones influence various vital processes in the body, including protein, fat, and Carbohydrate METABOLISM, Water-salt balance, cardiovascular Functions, and The Nervous system.

Hormones (such as the mineralocorticoid aldosterone) secreted by the Cells of the zona glomerulosa enhance the reabsorption of sodium and chloride from the primary urine in renal nephrons while reducing potassium reabsorption. Consequently, blood sodium concentration increases, leading to water retention in Tissues. In cases of insufficient production and low secretion of mineralocorticoids, sodium and chloride reabsorption decreases, causing the body to lose large amounts of water, which can lead to dehydration and death.

Glucocorticoids (hydrocortisone, cortisone, and corticosterone), secreted by the cells of the zona fasciculata, regulate protein, fat, and carbohydrate metabolism, increase blood sugar levels by promoting its synthesis from Proteins and fats in the Liver, and enhance fat mobilization from fat depots. Under The Influence of glucocorticoids, protein breakdown processes prevail over their synthesis. Glucocorticoids also maintain normal kidney function and accelerate primary Urine Formation in the renal corpuscles. Furthermore, glucocorticoids suppress inflammatory processes and allergic conditions, which is why they are referred to as anti-inflammatory hormones. These hormones increase stress resistance and facilitate the body's adaptation to adverse environmental factors. A deficiency in glucocorticoids reduces the body's resistance to various diseases, causing them to take a more severe course.

Sex Hormones (androgens, estrogens) produced in the zona reticularis of the adrenal glands manifest their effects during childhood, when the incretory function of the Gonads is still low, and in old age, during the involution of the gonads. During these periods of human life, The activity of the adrenal cortex's zona reticularis serves as the sole source of androgen and estrogen secretion.

The medulla synthesizes adrenaline and noradrenaline, which belong to catecholamines. Noradrenaline maintains vascular tone and also participates in the transmission of excitation from synaptic nerve endings to innervated Organs.

Adrenaline enhances and accelerates heart contractions and increases the excitability of the myocardium (heart Muscle). It constricts Blood Vessels (arterioles) in the Skin, skeletal Muscles, and Internal Organs. Under the influence of adrenaline, the MOTOR FUNCTION OF The Stomach and intestines is weakened. Adrenaline causes contraction of the smooth musculature of the biliary and urinary tracts, Uterus, Vagina, and the pupillary dilator muscle. Conversely, adrenaline relaxes bronchial smooth muscle, which is why this substance is used to treat bronchospasms and Bronchial Asthma. Affecting metabolism, adrenaline enhances The breakdown of Glycogen into glucose in The Liver and muscles. The resulting glucose enters the bloodstream and is utilized as an energy substrate.

Adrenaline helps increase the excitability of the nervous system's receptors, particularly the retina of the eye, as well as the organs of Hearing and Equilibrium. During strong emotions (severe cooling, sudden joy, excessive muscular tension, fear, anger), adrenaline release into the blood increases. This fact demonstrates the Influence of the nervous system—specifically its sympathetic division—on the Functions of the adrenal medulla.