Fetal Pig Blood Vessels and Circulation

Major Heart Chambers and Fetal Shunts

The fetal pig heart contains four chambers and specialized shunts that direct blood flow to bypass the nonfunctional fetal lungs. Understanding these structures is essential for tracing fetal circulation.

• Right Atrium: Receives blood returning to the heart from the body.

• Right Ventricle: Pumps blood into the pulmonary trunk.

• Left Atrium: Receives blood from the pulmonary veins.

• Left Ventricle: Pumps blood into the aorta.

• Foramen Ovale: Allows blood to flow from the right atrium to the left atrium, bypassing the lungs.

• Ductus Arteriosus: Connects the pulmonary trunk to the aorta, allowing blood to bypass the fetal lungs.

Blood Flow Pathway (Fetal):

• Placenta → Umbilical vein → Ductus venosus → Inferior vena cava → Right atrium → Foramen ovale → Left atrium → Left ventricle → Aorta

Additional info: The ductus venosus allows blood from the umbilical vein to bypass the liver and enter the inferior vena cava.

Major Fetal Pig Blood Vessels

• Pulmonary Trunk: Carries blood from the right ventricle toward the pulmonary arteries.

• Pulmonary Arteries: Carry oxygen-poor blood toward the lungs.

• Pulmonary Veins: Carry oxygen-rich blood from the lungs to the left atrium.

• Aorta: Carries blood from the left ventricle to the body.

• Brachiocephalic Trunk: Supplies blood toward the head, neck, and right forelimb.

• Common Carotid Arteries: Supply blood to the head and neck.

• Internal Jugular Veins: Drain blood from the brain and deeper structures of the head and neck.

• External Jugular Veins: Drain blood from superficial areas of the head and neck.

• Subclavian Arteries/Veins: Supply/drain blood to/from the forelimbs.

• Superior (Cranial) Vena Cava: Returns blood from the upper body to the right atrium.

• Inferior (Caudal) Vena Cava: Returns blood from the lower body to the right atrium.

• Common Hepatic Artery: Supplies oxygen-rich blood to the liver.

• Hepatic Vein: Drains blood from the liver into the inferior vena cava.

• Hepatic Portal Vein: Carries nutrient-rich blood from digestive organs to the liver.

• Renal Artery/Vein: Supply/drain blood to/from the kidneys.

• Umbilical Arteries: Carry oxygen-poor blood from the fetus to the placenta.

• Umbilical Vein: Carries oxygen-rich blood from the placenta to the fetus.

Human Systemic Arteries

Major Arteries: Areas Supplied and Oxygenation

Arteries carry oxygenated blood away from the heart to various regions of the body. The following table summarizes the main arteries, their areas supplied, and their oxygenation status.

Human Systemic Veins

Major Veins: Areas Drained and Oxygenation

Veins carry deoxygenated blood toward the heart. The following table summarizes the main veins and their areas drained.

Key Distinction: The superior and inferior mesenteric veins drain into the hepatic portal system, so blood from the intestines passes through the liver before returning to the heart.

Respiratory System Structures

Fetal Pig Dissection: Respiratory Structures and Functions

The respiratory system is responsible for gas exchange and air conduction. Each structure has a specific function.

• Epiglottis: Covers the laryngeal opening during swallowing to prevent food entering the airway.

• Larynx: Allows air passage and produces sound.

• Trachea: Conducts air toward the bronchi.

• Lungs: Exchange oxygen and carbon dioxide with the blood.

• Diaphragm: Contracts and flattens to increase thoracic volume during inspiration.

• Heart: Pumps blood through pulmonary and systemic circulation.

• Pulmonary Trunk: Carries blood from the right ventricle toward the lungs.

• Pulmonary Veins: Return oxygen-rich blood from the lungs to the left atrium.

Pharynx and Larynx: Models and PAL

• Nasopharynx: Passageway for air from the nasal cavity.

• Oropharynx: Passageway for air and food behind the mouth.

• Laryngopharynx: Directs air toward the larynx and food toward the esophagus.

• Epiglottis: Prevents food from entering the airway during swallowing.

• Arytenoid Cartilage: Moves and positions the vocal folds.

• Thyroid Cartilage: Protects the vocal folds and supports the larynx.

• Cricoid Cartilage: Supports the larynx and keeps the airway open.

• True Vocal Folds (Vocal Cords): Vibrate to produce sound.

• False Vocal Folds (Vestibular Folds): Help protect and close the airway.

• Esophagus: Transports swallowed food to the stomach.

Bronchial Tree: Structure and Function

• Trachea: Carries air from the larynx to the primary bronchi.

• Tracheal Cartilages: Prevent the trachea from collapsing.

• Bronchial Cartilage: Keeps the bronchi open.

• Primary (Main) Bronchus: Carries air into each lung.

• Secondary (Lobar) Bronchus: Carries air to a lung lobe.

• Tertiary (Segmental) Bronchus: Carries air to a bronchopulmonary segment.

Order of Air Flow: Trachea → Primary bronchus → Secondary bronchus → Tertiary bronchus → Bronchioles → Alveoli

Pulmonary Circuit: Blood Flow and Oxygenation

• Right Pulmonary Artery: Carries oxygen-poor blood to the right lung.

• Left Pulmonary Artery: Carries oxygen-poor blood to the left lung.

• Right Pulmonary Vein: Returns oxygen-rich blood from the right lung to the left atrium.

• Left Pulmonary Vein: Returns oxygen-rich blood from the left lung to the left atrium.

• Pulmonary Trunk: Carries oxygen-poor blood out of the right ventricle.

Lungs and Pleura: Identification

• Apex of Lung: Pointed superior tip of lung.

• Base of Lung: Broad inferior surface resting on diaphragm.

• Horizontal Fissure: Separates right superior and middle lobes.

• Oblique Fissure: Separates the inferior lobe from upper lobes.

• Superior Lobe: Upper lung lobe.

• Middle Lobe: Middle lobe of the right lung only.

• Inferior Lobe: Lower lung lobe.

Heart Blood Flow Pathway

Blood flows through the heart in a specific sequence, ensuring oxygenation and circulation throughout the body.

• Right atrium → Tricuspid valve → Right ventricle → Pulmonary semilunar valve → Pulmonary trunk → Pulmonary arteries → Lungs → Pulmonary veins → Left atrium → Mitral valve → Left ventricle → Aortic semilunar valve → Aorta → Body → Venae cavae → Right atrium

Respiratory Volumes and Concepts

Key Definitions and Formulas

• Ventilation: Movement of air into and out of lungs.

• Inspiration: Movement of air into lungs.

• Expiration: Movement of air out of lungs.

• Tidal Volume (TV): Volume of a normal quiet breath.

• Expiratory Reserve Volume (ERV): Extra air forcibly exhaled after normal expiration.

• Inspiratory Reserve Volume (IRV): Extra air inhaled after normal inspiration.

• Residual Volume (RV): Air remaining after maximum expiration.

• Vital Capacity (VC): Maximum air exhaled after maximum inspiration.

• Total Lung Capacity (TLC): Total amount of air lungs can hold.

• Functional Residual Capacity (FRC): ERV + RV

• Inspiratory Capacity (IC): TV + IRV

Formulas:

Additional Concepts

• Pulmonary Surfactant: Reduces alveolar surface tension.

• Asthma Attack: Bronchiolar smooth muscle contracts, airway resistance increases, breathing becomes difficult, especially expiration.

• Heart Rate and R–R Interval: If heart rate increases, the R–R interval decreases.

• Blood Flow: Decreases with decreasing vessel radius or increasing vessel length.

• Fetal Circulation: The right atrium receives oxygen-rich blood returning from the placenta via the umbilical vein and inferior vena cava.

Exam Tip: For vessel questions, memorize three things together: structure name → where blood comes from/goes → oxygenated or deoxygenated. For respiratory questions, memorize structure name → one specific function.