Lymphatic System Structures

Overview of the Lymphatic System

The lymphatic system is a network of tissues and organs that help rid the body of toxins, waste, and other unwanted materials. Its primary function is to transport lymph, a fluid containing infection-fighting white blood cells, throughout the body.

• Thymus: A lymphoid organ located in the upper chest, important for the maturation of T-lymphocytes (T cells).

• Spleen: The largest lymphatic organ, filters blood, recycles old red blood cells, and helps fight infection.

• Lymph Nodes: Small, bean-shaped structures that filter lymph and house lymphocytes. Types include:

  • Cervical lymph nodes: Located in the neck.

  • Axillary lymph nodes: Located in the armpits.

  • Inguinal lymph nodes: Located in the groin.

• Lymphatic Vessels: Thin-walled vessels that carry lymph throughout the body.

• Pharyngeal/Adenoid Tonsil: Located in the nasopharynx, helps protect against inhaled pathogens.

• Palatine Tonsil: Located at the back of the throat, part of the immune system.

• Lingual Tonsil: Located at the base of the tongue.

• Appendix: Contains lymphoid tissue, may play a role in immune function.

• Right Lymphatic Duct: Drains lymph from the right upper limb, right side of thorax, and right halves of head and neck.

• Thoracic Duct: The largest lymphatic vessel, drains lymph from most of the body into the venous system.

• Cisterna Chyli: A dilated sac at the lower end of the thoracic duct, collects lymph from the lower limbs and intestines.

Direction of Lymph Flow

• Lymph flows from peripheral tissues toward the heart, entering the venous circulation via the right lymphatic duct and thoracic duct.

• Movement is aided by skeletal muscle contraction, valves in lymphatic vessels, and respiratory movements.

Example:

Lymph from the legs travels through lymphatic vessels, passes through inguinal lymph nodes, and eventually enters the cisterna chyli before draining into the thoracic duct.

Respiratory System Structures

Overview of the Respiratory System

The respiratory system is responsible for gas exchange, supplying oxygen to the blood and removing carbon dioxide. It consists of a series of organs and structures that facilitate breathing.

• Frontal Sinus: Air-filled cavity in the frontal bone, helps humidify and filter inhaled air.

• Hard Palate: Bony anterior portion of the roof of the mouth, separates oral and nasal cavities.

• Soft Palate & Uvula: Muscular posterior portion of the roof of the mouth; the uvula helps prevent food from entering the nasopharynx.

• Nasopharynx: Upper part of the pharynx, connects nasal cavity to oropharynx.

• Oropharynx: Middle part of the pharynx, behind the oral cavity.

• Laryngopharynx: Lower part of the pharynx, leads to the larynx and esophagus.

• Pharyngeal/Adenoid Tonsil: Immune tissue in the nasopharynx.

• Palatine Tonsil: Immune tissue at the sides of the oropharynx.

• Lingual Tonsil: Immune tissue at the base of the tongue.

• Hyoid Bone: U-shaped bone in the neck, supports the tongue and larynx.

• Thyroid Cartilage: Largest cartilage of the larynx, forms the Adam's apple.

• Cricoid Cartilage: Ring-shaped cartilage below the thyroid cartilage.

• Trachea: Windpipe, conducts air to the lungs.

• Epiglottis (function): Flap of cartilage that covers the trachea during swallowing, preventing food from entering the airway.

• Vestibular Ligament/Fold: False vocal cords, help close the larynx during swallowing.

• Vocal Ligament/Fold (function): True vocal cords, produce sound when air passes through.

• Glottis (function): Opening between the vocal cords, controls airflow and sound production.

Example:

During swallowing, the epiglottis closes over the glottis to prevent food from entering the trachea.

Cadaver Identification

Structures to Identify on a Human Cadaver

• Thymus

• Spleen

• Lymph nodes

• Lymphatic vessels

• Major respiratory structures (trachea, larynx, etc.)

Comparison Table: Lymphatic vs. Venous Structures

Key Equations

• Flow Rate in Vessels:

Where is the flow rate, is the velocity of fluid, and is the cross-sectional area of the vessel.

Additional info:

• Identification of structures on models and cadavers is essential for practical exams in Anatomy & Physiology.

• Understanding the direction of lymph flow and the distinction between lymphatic and venous systems is crucial for clinical applications.