Endocrine System, Blood, and Heart: Lab Review and Key Concepts

Endocrine System

Major Endocrine Organs

The endocrine system consists of glands that secrete hormones directly into the bloodstream to regulate body functions.

• Thyroid gland: Contains thyroid follicles filled with colloid and surrounded by follicular cells. Parafollicular cells secrete calcitonin.

• Pancreas: Has both exocrine and endocrine functions. Islets of Langerhans secrete hormones such as insulin and glucagon.

Histology: Identification of glandular structures and cell types is essential for understanding hormone production and secretion.

• Thyroid follicles: Spherical structures containing colloid, surrounded by follicular cells.

• Islets of Langerhans: Clusters of endocrine cells within the pancreas.

Example: The thyroid gland regulates metabolism through the secretion of thyroid hormones (T3 and T4).

Blood

Blood Smear Identification

Blood consists of various cell types, each with distinct functions and appearances under the microscope.

• Erythrocytes (Red Blood Cells): Biconcave, lack nuclei, transport oxygen.

• Leukocytes (White Blood Cells): Include neutrophils, lymphocytes, basophils, eosinophils, and monocytes. Each type has unique staining properties and functions in immunity.

• Thrombocytes (Platelets): Small cell fragments involved in clotting.

Blood Typing

Blood typing determines compatibility for transfusions and is based on the presence of specific antigens on erythrocytes.

• ABO system: Blood types A, B, AB, and O are determined by the presence or absence of A and B antigens.

• Rh factor: Positive or negative, based on the presence of the Rh antigen.

Example: Type O negative blood is considered the universal donor for red blood cell transfusions.

Components of Blood

• Plasma: Liquid portion containing water, proteins, nutrients, and hormones.

• Buffy coat: Thin layer containing leukocytes and platelets.

• Hematocrit: Percentage of blood volume occupied by erythrocytes.

Heart

Heart Anatomy and Dissection

The heart is a muscular organ responsible for pumping blood throughout the body. Understanding its anatomy is crucial for identifying its structures and functions.

• Major structures: Chambers (atria and ventricles), valves (tricuspid, bicuspid/mitral, pulmonary, aortic), vessels (aorta, vena cava, pulmonary arteries and veins).

• Dissection: Labeling and identification of heart structures in models and specimens.

Electrocardiogram (EKG/ECG)

An EKG records the electrical activity of the heart and is used to diagnose cardiac conditions.

• Key waves: P wave (atrial depolarization), QRS complex (ventricular depolarization), T wave (ventricular repolarization).

• EKG interpretation: Calculation of heart rate using R-R intervals.

$\text{Heart Rate} = \frac{60}{\text{R-R interval (seconds)}}$

Cardiac Arrhythmias

• Bradycardia: Slow heart rate.

• Tachycardia: Fast heart rate.

• Arrhythmia: Irregular heart rhythm.

• Ventricular Fibrillation (V.Fib): Disorganized electrical activity in the ventricles.

• Heart Block: Impaired conduction between atria and ventricles.

Example: A prolonged QRS complex may indicate a bundle branch block.

Additional info: These notes expand on the brief points provided, offering definitions, examples, and equations relevant to the study of the endocrine system, blood, and heart anatomy and physiology.