Human Body Systems: Cardiac and Respiratory Systems

Cavaties

  • Carnial

  • throratic

    • Heart - pericarduim

    • Lungs - Pleural

    • Abdominal/pelvic

Functions: Transportation of

  • Red blood cells: O_2/ CO_2

  • White blood cells: immune cells

  • Platelets: clotting/repair

  • Plasma:water: salts/proteins/sugar

Closed system

  • vessels(transport)

Flow in body:

  • Heart—>arteries—→Capilaraies—→Vein

Pump away gas exchange return

Position of the Heart in the Thorax

  • The heart is roughly the size of a human fist and weighs less than a pound.

  • Location: The heart is located in the thoracic cavity between the lungs in the inferior mediastinum, which is the medial section of the thoracic cavity.

  • **Orientation:

    • Apex:** The pointed region of the heart is directed toward the left hip and rests on the diaphragm.

    • Base: The wider area where the great blood vessels emerge points toward the right shoulder.

Dual System of the Human Blood Circulation

  • The circulatory system is a closed system consisting of the heart and blood vessels.

  • Roles:

    • Heart: Pumps blood throughout the body.

    • Blood Vessels: Facilitate circulation to all parts of the body.

  • Functions of the Cardiovascular System:

    • Transports oxygen, nutrients, cellular wastes, and hormones to and from cells.

Structure of Blood Vessels

  • Blood vessels share basic structures, differing mainly by function:

    • Arteries:

    • Structure: Thick walls and small lumens to handle high pressure.

    • Appearance in Cross-section: Round shape.

    • Veins:

    • Structure: Thinner walls and larger lumens accommodating low-pressure flow.

    • Appearance in Cross-section: Flattened shape.

    • Lumen: The central blood-filled space of vessels.

  • Important Note: A micrograph shows the relative differences in thickness between arteries and veins (LM×160).

Types of Blood Vessels

  1. Arteries: Carry blood away from the heart (e.g., smaller arterioles).

  2. Veins: Carry blood to the heart (e.g., smaller venules).

  3. Capillaries: Join arterioles to venules, acting as the sites of exchange.

Capillary Bed Dynamics

  • Exchange Mechanisms:

    • When sphincters are open, blood flows into capillaries for the exchange of substances.

    • When sphincters are closed, blood is diverted bypassing the capillary bed into a thoroughfare channel leading to venous circulation (vascular shunt).

  • Arteriovenous Anastomosis: A direct connection from an arteriole to a venule that bypasses the capillary bed.

  • Vasomotion: Refers to the irregular, pulsing blood flow through capillary beds.

Cardiovascular Circulation

  • Pulmonary Circuit:

    • Blood flows from the right side of the heart to the lungs and back to the left side of the heart.

    • Blood is pumped out of the right side through the pulmonary trunk which splits into pulmonary arteries to carry oxygen-poor blood to the lungs.

    • Oxygen-rich blood returns from the lungs to the heart via pulmonary veins.

  • Systemic Circulation:

    • Oxygen-rich blood returns to the left side of the heart and is pumped out into the aorta.

    • Blood circulates through systemic arteries to all body tissues.

    • The left ventricle has thicker walls because it pumps blood throughout the body, whereas oxygen-poor blood returns via systemic veins to the right atrium through the superior or inferior vena cava.

Natural Pacemaker of the Heart

  • The Sinoatrial (SA) Node is a mass of nervous tissue that times heartbeats.

  • The SA node triggers the contractions of the atria and sends signals to the Atrioventricular (AV) Node, which then signals the ventricles to contract.

Cardiovascular Disorders

  • Hypertension: High blood pressure increases the risk of heart attack, heart disease, and stroke.

  • Heart Disease: Often caused by fatty deposits that block arteries, making it the most common cause of death among Americans.

  • Anemia: A condition where blood lacks sufficient oxygen-carrying capacity.

  • Myocardial Infarction (Heart Attack): Occurs when coronary arteries become blocked, resulting in rapid death of heart muscle cells. This blockage often stems from a gradual process known as atherosclerosis involving plaque buildup.

Circulatory System Types

  • Open Circulatory System (a): Hemolymph circulates in sinuses and is not confined to vessels.

  • Closed Circulatory System (b): Blood is contained within vessels and circulates through the heart.

Circulation Types in Different Animals

  • Single Circulation: Present in sharks, rays, and bony fishes which have a two-chambered heart allowing blood to pass through two capillary beds before returning to the heart.

  • Double Circulation: Found in amphibians, reptiles, and mammals where oxygen-poor blood is pumped from the right side and oxygen-rich blood from the left side, operating in two separate circuits.

Function of Blood

  • Blood provides long-distance transportation throughout the body and is composed of:

    • Plasma: The liquid component, dissolving many small molecules and different types of cells.

    • Red Blood Cells: Transport oxygen using hemoglobin.

    • White Blood Cells: Play a vital role in fighting infections.

Oxygen Transport in Blood

  • In the lungs, oxygen ($O_2$) binds to a protein in red blood cells called hemoglobin.

  • The red color of blood is due to iron bound to the heme group in hemoglobin.

Clotting Mechanism in Blood

  • Blood contains self-sealing substances that react to injuries.

  • Platelets: Quickly form a sticky plug to seal minor breaks.

  • Fibrin: Molecules cross-link to form a clot; when on the surface of skin, this is referred to as a scab.

Basic Anatomy of the Upper Respiratory Tract

  • Sagittal Section Features:

    • Regions of the Pharynx:

    • Nasopharynx

    • Oropharynx

    • Laryngopharynx

Detailed Anatomy of Upper Respiratory Tract

  • Key Structures:

    • Cribriform plate of the ethmoid bone

    • Sphenoidal sinus

    • tryngeal tonsil and various tonsils (palatine and lingual)

    • Larynx components including the epiglottis, vocal folds, thyroid cartilage, and cricoid cartilage.

Functional Anatomy of the Respiratory System

  • Gas exchanges between the blood and external environment occur specifically in the alveoli of the lungs.

  • Respiratory Tract:

    • Upper respiratory tract consists of passageways from the nose to the larynx.

    • Lower respiratory tract includes passageways from trachea to alveoli, which serve to purify, humidify, and warm incoming air.

Respiratory Zone Structures

  • Comprises:

    • Alveolar duct

    • Respiratory bronchioles

    • Terminal bronchioles

    • Alveoli, where gas exchange occurs

Respiratory Membrane (Air-Blood Barrier)

  • Structure and function involve:

    • Alveoli filled with gas

    • Interaction with red blood cells in capillaries.

    • Components include alveolar epithelium, fused basement membranes, and capillary endoth elium, ensuring efficient gas exchange.

Respiratory System Disorders

  • Emphysema: Often results from long-term tobacco smoke or air pollution exposure.

  • Bronchitis: Most commonly caused by viral infections affecting the bronchioles.

  • Upper Respiratory Infections (URIs): Caused by either viruses or bacteria.

  • Asthma: A chronic inflammation of the airways.

Breathing Mechanisms in Unique Animals

  • Birds: Have air sacs that function like bellows, allowing for one-way air flow through lungs, requiring two cycles of inhalation and exhalation for effective ventilation.

  • Fish: Utilize gills for gas exchange, where water flows over gill filaments allowing oxygen to diffuse into the blood.

  • Gastrovascular Cavities: Animals like cnidarians rely on these structures, which serve dual functions in both digestion and distribution of substances, benefiting organisms with thin bodies that minimize diffusion distances.