LAB PRACTICAL 1

The Endocrine System

The Nervous system & Endocrine system work together to regulate physiological events throughout the body

Endocrine system releases Hormones (Chemical Messengers)

• Hormones are released by ductless endocrine glands into the bloodstream

Endocrine organs made of nervous tissue are called Neuroendocrine Organs, whose main function is to release Neurohormones

Humoral Control - hormones are released in response to the concentration of certain substances (glucose or calcium ions) in the blood

Neural Control - hormones are released in response to electrical impulses

Hormonal Control - hormones are released in response to other hormones

Endocrine disorders result when a gland produces too little or too much of a specific hormone

• This is usually called a Hormone Imbalance

Hormone imbalances are usually corrected via Feedback Mechanisms

GLANDS OF ENDOCRINE SYSTEM

1 - Hypothalamus

• In the diencephalon of the brain

• Major homeostatic organ that regulates BP, hunger, thirst, body temp., & some reproductive functions

• Releases Releasing & Inhibiting hormones

  • Any hormone that ends in RH or IH

Hypothalamic Hormones

Hormone               Target        Action

2 - Pituitary Gland

• Extends from the hypothalamus via the stalk-like infundibulum

• Sits in the Sphenoid Bone in the skull

• It consists of 2 Lobes

  • Anterior Pituitary Gland (adenohypophysis)

    • Composed of Epithelial Tissue

  • Posterior Pituitary Gland (neurohypophysis)

    • Consists of Nervous Tissue 

      Pituitary Hormones

3 - Pineal Gland

• Small cone-shaped organ

• Secretes Melatonin (controls sleep/wake cycle, aka Circadian Rhythm)

• Exact role is humans is still controversial

4 - Thymus

• Irregularly shaped gland in the mediastinum

• Produces Thymosin & Thymopoietin

• Maturation of T-lymphocytes

• Thymus is large in children, but begins to atrophy (shrink) at puberty

• Mostly replaced by adipose & fibrous CT’s

5 - Thyroid Gland

• Bi-lobed organ in front of trachea and below thyroid cartilage (Adam’s apple) 

• Lobes are connected by Isthmus

• Consists of thyroid follicles that are filled with iodine-rich gelatinous material called Colloid

• Lined with simple cuboidal epithelial cells called Follicle Cells

• TSH from the anterior pituitary stimulates follicle cells to secrete thyroglobulin, a precursor molecule that is then combined with iodine molecules to produce the thyroid hormone Triiodothyronine (T3) & Thyroxine (T4)

• Thyroid hormones regulate metabolic rate & thermoregulation, also promote growth and development

• Between the follicles are Parafollicular Cells that secrete Calcitonin (a hormone that lowers blood calcium levels) 

6 - Parathyroid Gland

• Embedded on the back of the thyroid gland

• 3-5 pea-shaped structures called Parathyroid Glands

• Secrete Parathyroid Hormone (PTH)

• PTH elevates blood calcium levels by targeting bones, kidneys, & small intestine

• PTH stimulates osteoclasts to break down bone & release calcium into the blood

• PTH stimulates the absorption of calcium from food into the bloodstream

7 - Adrenal Glands

• Pyramid shaped

• Above the kidneys

• Each adrenal gland is composed of 2 separate regions: an outer Adrenal Cortex & inner Adrenal Medulla

• The outer Adrenal Cortex has 3 distinct zones–the Zona Glomerulosa, the Zona Fasciculata, & the Zona Reticularis (each produces a steroid hormone derived from cholesterol)

Zona Glomerulosa 

• Balls of cells that produce Mineralcorticoids (regulate mineral balance)

• Aldosterone - Main: Mineralcorticoid

  • Stimulates cells of kidneys to reabsorb sodium ions; water then follows the resorbed sodium ions via osmosis

  • Blood Volume & BP Increases

  • Urine Volume Decreases

Zona Fasciculata

• Bundles of cells that produce Glucocorticoids (regulate glucose metabolism & androgenic steroids)

• Cortisol - Main Glucocorticoid

  • Targets liver, muscle, & adipose tissue

  • Cortisol's actions include: Gluconeogenesis (production of glucose from amino acids & fatty acids) in the liver; Breakdown of muscle proteins to release amino acids into the bloodstream; Breakdown of lipids to release fatty acids into the bloodstream

Zona Reticularis

• Network of cells that produce both glucocorticoids & androgenic steroids

  • Androgenic steroids produced by the Gonads

• Chromaffin Cells of adrenal medulla produce 2 catecholamines: Epinephrine & Norepinephrine (neurohormones that control fight-or-flight response to stress)

8 - Pancreas

• Club-shaped gland located behind the stomach

• It’s both an Endocrine AND Exocrine gland

  • Exocrine cells are called Acinar Cells

• Pancreatic Islets = Hormone-producing portion of the pancreas

  • Contain Alpha & Beta cells (produce hormones to regulate blood glucose levels)

• The Alpha (α) cells secrete Glucagon (raises blood glucose levels)

• The Beta (β) cells secrete Insulin (lowers blood glucose levels)

• The Delta (δ) cells secrete Somatostatin (a hormone identical to the hormone produced in the hypothalamus)

9 - Testes & Ovaries

Testes (male gonads)

• 2 major functions: Gamete (sperm) production & Testosterone

• GnRH released into the bloodstream reaches the anterior pituitary gland, where it stimulates Gonadotropins: FSH & LH, which target testis

  • FSH aids in sperm development

  • LH stimulates testosterone secretion

Ovaries (female gonads)

• 2 major functions: production of gametes (oocytes) & production of Estrogen & Progesterone

• In females, FSH stimulates gamete formation & release of estrogens

• LH stimulates the secretion of estrogens & progesterones

  • They’re responsible for secondary sex characteristics (breast development & adipose tissue around hips & thighs)

Blood

Blood is Connective Tissue consisting of 2 components:

• Formed Elements (RBC’s, WBC’s, & platelets)

• Plasma (a fluid extracellular matrix composed primarily of water)

Hemodynamics = Physiology of blood flow

Blood's functions can be put into 3 categories: Delivery, Regulatory, & Protective functions

• Blood delivers oxygen & nutrients to body cells, carbon dioxide & waste products to their elimination sites (lungs & kidneys)

• Blood plays an important role in homeostasis, like the regulation of body temperature, pH, & BP

• Blood’s protective functions include immunity & blood clotting

Mature Erythrocytes look like biconcave discs, are anucleate cells (one nucleus) packed with hemoglobin (pigment that transports both oxygen and a small % of carbon dioxide)

The cell membrane of RBC’s are associated with a flexible protein called Spectrin, which enables RBC’s to squeeze through the smallest of capillaries

RBC’s are produced in the red bone marrow, like all formed elements

5 Different types of Leukocytes:

• Neutrophils

• Lymphocytes

• Monocytes

• Eosinophils

• Basophils

Never Let My Engines Blow

60% 30% 5(4-8%) 3%  0%  

GRANULOCYTES:

Neutrophils

• Nucleus has 3-5 lobes (multilobed nucleus)

• Cytoplasmic granules do not stain

• Functions mainly in Phagocytosis

• Numbers rise during Viral Infection (VIN)

Eosinophils

• Have cytoplasmic granules that stain Red with acidic dyes

• Bilobed nucleus, similar in size to Neutrophils

• Increase during Parasitic infections & Allergic reactions (PAE)

Basophils

• Least numerous in WBCs

• Contain cytoplasmic granules that stain dark purple with basic dyes

• S-shaped nucleus

• Basophils sometimes pass through intact blood vessel walls into the surrounding tissues, a process called Diapedesis

• When Basophils migrate into tissues, they become Mast Cells

  • Mast cells produce many substances, like histamine, a chemical that enhances the inflammatory response

AGRANULOCYTES (lack brightly staining granules)

Lymphocytes

• Play an active role in the immune response

• Thin rim of light blue cytoplasm becomes visible when cell is stained

• Small cell; nucleus takes up most of the cell's volume

• 2 types of lymphocytes:

  • B Lymphocytes - mediate the immune response via production of antibodies

  • T Lymphocytes - act via direct cellular attack

Monocytes

• Largest of the Leukocytes

• Light blue to purple cytoplasm becomes visible when cell is stained

• Large U-shaped nucleus

• Monocytes also migrate via Diapedesis into the tissues, where they become Macrophages that attack and destroy bacteria & viruses via phagocytosis

Formed elements called Platelets (or thrombocytes) are fragments of large multinucleate cells called Megakaryocytes, located in red bone marrow

When blood vessels are damaged, Platelets mediate the process of blood clotting, or coagulation, to prevent excessive blood loss. 

Coagulation is only one part of Hemostasis, a multi-step process that leads to the stoppage of bleeding

Hemostasis involves a positive feedback mechanism based on the interaction of a variety of substances, like plasma proteins & chemicals released by platelets and damaged body cells.

Hematocrit = Percentage of erythrocytes in a volume of blood sample

“Rh” in the Rh system stands for Rhesus Monkey

If Anti-A serum clumps A antigen is present.

If Anti-B serum clumps B antigen is present.

If Anti-Rh serum clumps Rh factor is positive (+).

Anatomy of the Heart 

Make sure to go over heart diagrams

The heart is a fist-sized, four-chambered muscular pump lying within the mediastinum of the thoracic cavity

Surrounded by a double-layered membrane called the Pericardium

Blood vessels enter & leave the heart at its broad Base, and the inferior tip of the heart is called the Apex

The pericardium has an outer layer (Fibrous Pericardium) that anchors the heart to surrounding structures

• It also has the inner Serous Pericardium composed of 2 layers separated by a narrow serous fluid-filled cavity called the pericardial cavity

Pericardial Fluid reduces friction during muscular contraction

The outer layer of serous pericardium, the Parietal Pericardium, is fused to the fibrous pericardium

The inner layer of serous pericardium, the Visceral Pericardium, is attached to the heart muscle and forms the Epicardium, the outer layer of the heart wall

In addition to the epicardium, the heart wall is composed of the Myocardium, the middle layer containing primarily cardiac muscle tissue

The Endocardium rests on a thin layer of areolar CT, and it is continuous with the innermost lining of blood vessels throughout the body

Atria = 2 superior thin-walled chambers; receive & direct blood coming into the heart

On the outer surface of each atrium is a flap-like structure called an Auricle, which expands to increase atrial volume

Right Atrium receives oxygenated blood from the four pulmonary veins of the pulmonary circuit

• Lining the right atrium are comb-like muscular ridges called Pectinate Muscles

The atria are separated by a thin wall called Interatrial Septum

• A depression in the interatrial septum called the Fossa Ovalis is the remnant of the Foramen Ovale, an opening between the right and left atria by which the pulmonary circuit is bypassed in the fetus

Ventricles = 2 inferior thick-walled chambers that pump blood

Right Ventricle receives deoxygenated blood from the right atrium and pumps it into the pulmonary circuit via the Pulmonary Trunk

Ligamentum Arteriosum  = band of CT where the pulmonary trunk branches into the right pulmonary artery and left pulmonary artery

• Remnant of the ductus arteriosus, a fetal blood vessel that shunts blood from the pulmonary trunk to the aorta, bypassing the lungs

Left Ventricle receives oxygenated blood from the left atrium and pumps it into the systemic circuit via the ascending aorta

Both ventricular walls are characterized by the presence of a distinct network of muscular ridges, called Trabeculae Carnae

Tricuspid Valve (or right atrioventricular valve) - prevents backflow of blood from the right ventricle to the right atrium

Mitral (Bicuspid) Valve (or left atrioventricular valve) - prevents backflow of blood from the left ventricle to the left atrium

Pulmonary Valve (or pulmonary semilunar valve) within the pulmonary trunk and the aortic valve (or aortic semilunar valve) within the aorta–open when the contracting ventricles pump blood into the arteries and then close to prevent blood from flowing back into the ventricles

Tricuspid & Mitral (Bicuspid) valves are anchored to the Papillary Muscles of the ventricular wall by structures called Chordae Tendineae

The Great Vessels that carry blood away from and return blood to the heart are the largest blood vessels of the body

Superior Vena Cava - drains deoxygenated blood from veins ABOVE the diaphragm

Inferior Vena Cava - drains deoxygenated blood from veins BELOW the diaphragm

The Pulmonary Trunk rises from the right ventricle & splits into right and left pulmonary arteries, which carry deoxygenated blood to the right and left lungs

Pulmonary Veins transport oxygenated blood back to the heart, they empty into the left atrium (most people have 2 in the right lung & 2 in the left lung)

Aorta (largest artery in the body) - rises from the left ventricle and carries oxygenated blood AWAY from the heart

• Aorta is divided into ascending aorta, aortic arch, and the descending aorta

Deoxygenated blood ejected into the pulmonary trunk by the right ventricle enters the Pulmonary Circuit

Oxygenated blood pumped by the left ventricle through the aorta enters the Systemic Circuit

A branch of the systemic circuit, the Coronary Circulation–supplies the myocardium with the oxygen and nutrients needed for muscle contraction.

The right and left coronary arteries branch from the Ascending Aorta and encircle the heart in the atrioventricular (coronary) sulcus.

The right coronary artery branches into the marginal artery and the posterior interventricular artery. 

The left coronary artery branches into the circumflex artery and the anterior interventricular artery

Capillaries drain into venules, which fuse to form veins

The myocardium is drained by the great, middle, and small cardiac veins, all of which eventually empty into the Coronary Sinus, which drains into the right atrium

Heart Structures & Internal Features

• Auricle: Flap-like structure on the outer surface of each atrium that expands to increase atrial volume.

• Pectinate Muscles: Comb-like muscular ridges lining the right atrium that provide extra strength to the atrial wall.

• Interatrial Septum: Thin wall separating the right and left atria.

• Fossa Ovalis: A depression in the interatrial septum; remnant of the fetal foramen ovale.

• Trabeculae Carneae: Distinct network of muscular ridges lining the inner walls of the ventricles.

• Chordae Tendineae: Tendinous cords anchored to papillary muscles that support the atrioventricular valves.

• Papillary Muscles: Ventricular wall muscles that anchor the chordae tendineae to prevent valve prolapse.

Heart Valves

• Tricuspid Valve (Right AV Valve): Prevents backflow of blood from the right ventricle into the right atrium.

• Mitral / Bicuspid Valve (Left AV Valve): Prevents backflow of blood from the left ventricle into the left atrium.

• Pulmonary Semilunar Valve: Located within the pulmonary trunk; prevents backflow of blood into the right ventricle.

• Aortic Semilunar Valve: Located within the aorta; prevents backflow of blood into the left ventricle.

Great Blood Vessels

• Superior Vena Cava: Drains deoxygenated blood from regions superior to the diaphragm into the right atrium.

• Inferior Vena Cava: Drains deoxygenated blood from regions inferior to the diaphragm into the right atrium.

• Pulmonary Trunk & Arteries: Carry deoxygenated blood from the right ventricle toward the lungs.

• Pulmonary Veins: Four veins (two per lung) that transport oxygenated blood from the lungs into the left atrium.

• Aorta: Largest artery in the body; carries oxygenated blood from the left ventricle to systemic circulation.

• Ligamentum Arteriosum: Connective tissue bridge between the pulmonary trunk and aorta; remnant of the fetal ductus arteriosus.

Circulatory Pathways

• Pulmonary Circuit: Path that carries deoxygenated blood to the lungs for gas exchange and returns oxygenated blood to the left atrium.

• Systemic Circuit: Path that delivers oxygenated blood from the left ventricle to all body tissues and returns deoxygenated blood to the right atrium.

• Coronary Circulation: Branch of the systemic circuit supplying oxygen and nutrients directly to the myocardium.

• Coronary Sinus: Large vessel on the posterior heart that drains blood from cardiac veins directly into the right atrium.

Coronary Blood Supply

• Right Coronary Artery: Branches into the marginal artery and posterior interventricular artery.

• Left Coronary Artery: Branches into the circumflex artery and anterior interventricular artery (clinically known as LAD).

• Cardiac Veins (Great, Middle, Small): Drain blood from the myocardium and empty into the coronary sinus.

Cardiac Conduction & ECG

• Sinoatrial (SA) Node: Pacemaker of the heart; located in the right atrium; generates impulses that spread across the atria.

• Atrioventricular (AV) Node: Located in the floor of the right atrium; delays the action potential before sending it to the ventricles.

• Purkinje Fiber System: Conduction pathway comprising the AV bundle, right/left bundle branches, and terminal Purkinje fibers to excite the ventricular myocardium.

• Electrocardiogram (ECG/EKG): Graphic recording of the electrical activity occurring in the cardiac muscle over time.

• P Wave: Small upward deflection representing atrial depolarization.

• QRS Complex: Represents ventricular depolarization (masks atrial repolarization).

• T Wave: Upward deflection representing ventricular repolarization.

• Bradycardia: Heart rate below 60 bpm.

• Tachycardia: Heart rate above 100 bpm.

• Auscultation: Process of listening to heart sounds using a stethoscope.

General Blood Vessel Types

• Arteries: Vessels that carry blood away from the heart.

• Arterioles: Small arterial branches that lead into capillary beds.

• Capillaries: Microscopic exchange sites for gases, nutrients, and wastes.

• Venules: Small vessels that drain capillary beds and empty into larger veins.

• Veins: Vessels that carry blood back toward the heart.

Systemic Arteries

• Aortic Arch Branches: Gives rise to the brachiocephalic artery, left common carotid artery, and left subclavian artery.

• External Carotid Artery: Supplies tissues of the face, scalp, and neck.

• Internal Carotid Artery: Enters the skull through temporal bones to supply the brain.

• Vertebral Arteries: Arise from the subclavian arteries, pass through transverse foramina, and fuse to form the basilar artery.

• Axillary Artery: Continuation of the subclavian artery through the axilla (armpit).

• Brachial Artery: Main artery of the arm; splits into the radial and ulnar arteries.

• Radial & Ulnar Arteries: Supply the forearm and hand; form the deep and superficial palmar arches.

• Celiac Trunk: Unpaired branch of the abdominal aorta that supplies the stomach, liver, gallbladder, spleen, and duodenum.

• Superior Mesenteric Artery: Supplies most of the small intestine and part of the large intestine.

• Inferior Mesenteric Artery: Supplies the distal portion of the large intestine and rectum.

• Common Iliac Arteries: Terminal branches of the abdominal aorta; each splits into an internal iliac (pelvis) and external iliac (lower limb).

• Femoral Artery: Continuation of the external iliac artery in the thigh; becomes the popliteal artery behind the knee.

• Anterior & Posterior Tibial Arteries: Branches of the popliteal artery; anterior becomes the dorsalis pedis artery at the ankle.

• Fibular Artery: Arises from the posterior tibial artery and supplies the lateral leg.

Systemic Veins

• Dural Sinuses: Veins draining blood from the brain into the internal jugular veins.

• Internal Jugular Vein: Drains blood from the brain, face, and neck.

• External Jugular Vein: Drains superficial tissues of the head and neck into the subclavian vein.

• Brachiocephalic Veins: Formed by the union of internal jugular and subclavian veins; combine to form the superior vena cava.

• Basilic & Cephalic Veins: Superficial veins of the upper limb; basilic runs medially, cephalic runs laterally.

• Median Cubital Vein: Anastomosing vein at the anterior elbow connecting the cephalic and basilic veins (common site for venipuncture).

• Azygos System: Network (azygos, hemiazygos, accessory hemiazygos) draining thoracic structures into the superior vena cava.

• Great Saphenous Vein: Longest vein in the body; superficial vein running along the medial leg and thigh into the femoral vein.

• Small Saphenous Vein: Superficial vein on the lateral calf emptying into the popliteal vein.

• Tunics: The three structural layers (tunics) that compose the walls of arteries and veins.

  
  

  
  

• Tunica Intima: The innermost layer lining the vessel lumen; composed of simple squamous epithelium (endothelium) and a thin layer of loose connective tissue (basal lamina).

  
  

  
  

• Tunica Media: The middle layer composed primarily of smooth muscle and elastic fibers; innervated by the sympathetic nervous system to regulate vessel diameter.

  
  

  
  

• Tunica Externa: The outermost layer composed of dense irregular collagenous connective tissue; supports and protects the blood vessel.

  
  

  
  

• Lumen: The central, open space inside a blood vessel through which blood flows.

  
  

  
  

Capillary Wall Structure: Capillary walls are only one cell layer thick, consisting solely of endothelium sitting on a thin basal lamina to facilitate rapid gas and nutrient exchange.

Lower Limb Vein Drainage Quick-Reference

• Femoral Vein: Drains the thigh/knee region and empties into the external iliac vein.

  
  

  
  

• Popliteal Vein: Drains the posterior knee region and empties into the femoral vein.

  
  

  
  

• Anterior Tibial Vein: Drains the anterior leg/ankle and empties into the popliteal vein.

  
  

  
  

• Posterior Tibial Vein: Drains the posterior leg/plantar region and empties into the popliteal vein.

  
  

  
  

• Fibular Vein: Drains the lateral leg and empties into the posterior tibial vein.

  
  

  
  

• Dorsalis Pedis Vein: Drains the dorsal foot/ankle region and continues as the anterior tibial vein.