Cardiovascular and Respiratory System: Blood Flow, Heart, Vessels, and Lung Anatomy

Brachiocephalic Artery

This is the first branch off the aortic arch. It quickly divides into the Right Subclavian Artery (supplies the right arm) and the Right Common Carotid Artery (supplies the right side of the head and neck).

Left Common Carotid Artery

Supplies the left side of the head and neck.

Left Subclavian Artery

Supplies the left arm.

Thoracic Aorta

Supplies the chest wall, esophagus, bronchi, lungs, and mediastinum.

Abdominal Aorta

Supplies the abdominal organs and lower limbs.

Common Iliac Arteries

These are the terminal branches of the abdominal aorta. They divide into the internal and external iliac arteries. The internal iliac supplies the pelvic organs, while the external iliac becomes the femoral artery, supplying the lower limb.

Coronary Sinus

Drains blood from the heart muscle itself (myocardium).

Superior Vena Cava (SVC)

Drains blood from the head, neck, upper limbs, and thorax.

Inferior Vena Cava (IVC)

Drains blood from the abdomen, pelvis, and lower limbs.

Order of blood flow through the heart

Superior and Inferior Vena Cava → Right Atrium → Tricuspid Valve → Right Ventricle → Pulmonary Valve → Pulmonary Trunk → Pulmonary Arteries → Lungs → Pulmonary Veins → Left Atrium → Mitral Valve (Bicuspid Valve) → Left Ventricle → Aortic Valve → Aorta → Body.

Function of valves

Valves ensure unidirectional blood flow through the heart. They prevent backflow. The heart's valves include the tricuspid, mitral (bicuspid), pulmonary, and aortic valves.

Right Coronary Artery

Supplies the right atrium, right ventricle, and part of the left ventricle.

Left Coronary Artery

Divides into the left anterior descending artery (supplies the anterior walls of both ventricles and the interventricular septum) and the circumflex artery (supplies the left atrium and the posterior and lateral walls of the left ventricle).

Coronary Veins

Great cardiac vein, middle cardiac vein, and small cardiac vein drain into the coronary sinus, which then empties into the right atrium.

Pulmonary Circulation

Carries blood from the right ventricle to the lungs for oxygenation and back to the left atrium.

Systemic Circulation

Carries oxygenated blood from the left ventricle to the rest of the body and returns deoxygenated blood to the right atrium.

Blood flow from the aorta to the fingers/toes

Aorta → Major arteries (e.g., subclavian, brachial, radial, ulnar for the arm; femoral, popliteal, tibial, fibular for the leg) → Smaller arteries → Arterioles → Capillaries (where exchange occurs) → Venules → Veins → Vena Cava.

Celiac Trunk

Supplies the liver, stomach, spleen, and part of the duodenum. It's located in the upper abdomen.

Hepatic Portal System

Blood from the digestive organs (stomach, intestines, spleen, pancreas) flows into the hepatic portal vein, which carries it to the liver. In the liver, the blood is filtered and processed.

Hepatic veins

Blood vessels that drain blood from the liver into the inferior vena cava.

Tunica Intima

Innermost layer of blood vessels, consisting of endothelium.

Tunica Media

Middle layer of blood vessels, made up of smooth muscle and elastic fibers.

Tunica Externa (Adventitia)

Outermost layer of blood vessels, composed of connective tissue.

General flow pattern of blood

Arteries → Arterioles → Capillaries → Venules → Veins.

Function of the Heart

The heart is a muscular organ that pumps blood throughout the body, supplying oxygen and nutrients while removing carbon dioxide and waste products.

Arteries

Blood vessels that carry oxygen-rich blood away from the heart to the tissues.

Veins

Blood vessels that carry oxygen-poor blood back to the heart.

Capillaries

Tiny blood vessels where the exchange of oxygen, carbon dioxide, nutrients, and waste occurs between blood and tissues.

Location of the Heart

The heart is located in the thoracic cavity, between the lungs and behind the sternum.

Epicardium

The outer layer of the heart wall.

Myocardium

The middle layer of the heart wall, consisting of cardiac muscle tissue, responsible for the heart's contractions.

Endocardium

The inner layer lining the heart chambers.

Coronary Circulation

The Right Coronary Artery supplies blood to the right side of the heart, while the Left Coronary Artery branches into the left anterior descending artery and the circumflex artery, supplying the left side of the heart.

Hypothalamo-hypophyseal tract

This is a bundle of axons that originates from neurons in the hypothalamus and extends directly into the posterior pituitary gland. These neurons synthesize hormones (like ADH and oxytocin) in their cell bodies within the hypothalamus.

Hypothalamo-hypophyseal portal system

This is a special circulatory system that connects the hypothalamus with the anterior pituitary gland. Neurons in the hypothalamus secrete releasing and inhibiting hormones into this portal system.

Releasing hormones

Hormones secreted by the hypothalamus that stimulate the release of specific hormones from the anterior pituitary gland.

Inhibiting hormones

Hormones secreted by the hypothalamus that inhibit the release of specific hormones from the anterior pituitary gland.

Thyroid Hormone (T3/T4)

Released from the thyroid gland, it increases basal metabolic rate, stimulates protein synthesis, accelerates growth, and affects nervous system development.

Hypothyroidism

A disorder characterized by an underactive thyroid.

Hyperthyroidism

A disorder characterized by an overactive thyroid.

Calcitonin

Released from the thyroid gland (parafollicular cells), it reduces blood calcium levels by inhibiting bone resorption.

Insulin

Released from the pancreas (beta cells), it lowers blood glucose levels by promoting glucose uptake by cells and glycogen storage.

Diabetes mellitus

A disorder that includes Type 1 and Type 2 diabetes, characterized by high blood glucose levels.

Epinephrine

Released from the adrenal medulla, it increases heart rate, constricts blood vessels, dilates airways, and increases metabolic rate (fight-or-flight response).

Aldosterone

Released from the adrenal cortex, it increases sodium and water reabsorption, and potassium excretion, leading to increased blood volume and pressure.

Hyperaldosteronism

Excessive aldosterone production.

Hypoaldosteronism

Insufficient aldosterone production.

Antidiuretic Hormone (ADH)

Hormone released from the posterior pituitary gland that conserves body water by reducing urine output.

Diabetes insipidus

A disorder caused by ADH deficiency.

Parathyroid Hormone (PTH)

Hormone released from the parathyroid glands that increases blood calcium levels.

Hyperparathyroidism

Excessive PTH production.

Hypoparathyroidism

Insufficient PTH production.

Oxytocin

Hormone released from the posterior pituitary gland that stimulates uterine contractions and milk ejection.

Growth Hormone (GH)

Hormone released from the anterior pituitary gland that promotes growth of bone, muscle, and other tissues.

Gigantism

Condition caused by excessive GH before puberty.

Acromegaly

Condition caused by excessive GH after puberty.

Growth hormone deficiency

Condition also known as dwarfism.

Upper Respiratory Tract

Air enters through the nose/nasal cavity, passes through the pharynx, and into the larynx.

Lower Respiratory Tract

Air moves into the trachea, which branches into the right and left main bronchi.

Functions of the Nose

Includes airway passage, humidification & filtration, olfaction, and resonance.

Nasopharynx

Region of the pharynx that is air only and lined with ciliated epithelium.

Oropharynx

Region of the pharynx that is for both air and food, lined with stratified squamous epithelium.

Laryngopharynx

Region of the pharynx that is for both air and food, lined with stratified squamous epithelium.

Trachea

Structure that keeps open with cartilage rings and is lined with pseudostratified ciliated columnar epithelium.

Conducting Zone

Includes all airways down to the terminal bronchioles where no gas exchange occurs.

Respiratory Zone

Begins at respiratory bronchioles and includes alveoli where gas exchange happens.

Respiratory Membrane

Consists of alveolar epithelium, capillary endothelium, and fused basement membranes.

Lungs

Right lung has 3 lobes; left lung has 2 lobes.

Pleural Membrane

Includes parietal pleura lining the thoracic wall and visceral pleura covering the lungs.