Anatomy of the Respiratory and Urinary Systems

Posted on May 14, 2024 in Biology

Larynx

A tubular organ that connects the pharynx to the trachea, located in front of the neck. During swallowing, communication is intercepted by a layer of cartilage (epiglottis) that prevents food from passing into the airways. It consists of the hyoid bone and cartilage:

Cartilages of the Larynx

  • Cricoid: Superimposed on the trachea. It is a ring with a bow front and rear seal.
  • Thyroid: Forms the laryngeal prominence.
  • Epiglottis: When the larynx descends during swallowing, it is applied against the base of the tongue.
  • Arytenoid: It gives the vocal process insertion to the vocal cord, and the muscular process provides insertion for skeletal muscle.
  • Corniculate
  • Cuneiform

Pharynx

A muscular tube that aids in breathing and is located in the neck, connecting the nose and mouth with the trachea and esophagus. It serves as a passageway for both air and food, making it part of both the respiratory and digestive tracts. The pharynx is supported by a muscle, the constrictor muscles of the pharynx. It is lined by a mucous membrane that varies depending on the area:

Parts of the Pharynx

  • Nasopharynx: Continuously open to the air.
  • Oropharynx: Flanked by the palatine tonsils.
  • Hypopharynx: Two tubes lead anatomically ahead: the larynx and the esophagus behind.

Esophagus

Starts in the neck, crosses the entire chest, and passes into the abdomen through the esophageal hiatus of the diaphragm. Its function is to act as a duct junction between the mouth and stomach, allowing food to reach the stomach.

Layers of the Esophagus

  • Mucosa: Several layers of cells.
  • Muscularis: An inner layer of smooth muscle cells and a concentric outer layer of longitudinal muscle cells, where peristaltic waves form that drive the bolus into the stomach.

Sphincters of the Esophagus

  • Lower esophageal sphincter: Between the esophagus and stomach.
  • Upper esophageal sphincter: Between the pharynx and esophagus.

Parts of the Esophagus

  • Cervical
  • Thoracic
  • Abdominal

Other Features of the Esophagus

  • Irrigation: Esophageal arteries and varices.
  • Innervation: Vagus nerve.
  • Lymphatic drainage: Left gastric lymph nodes.

Stomach

Acts as a mixer and a reservoir, ultimately performing enzymatic digestion.

Parts of the Stomach

  • Cardia: Opening of the esophagus into the stomach.
  • Fundus: Dilated upper portion that relates to the left dome of the diaphragm.
  • Body
  • Pyloric part: Controls the discharge of gastric contents through the pyloric orifice into the duodenum.
  • Lesser curvature: Convex and shorter edge.
  • Greater curvature: Longer edge.

Kidney

Bean-shaped excretory organs located on the posterior abdominal wall on either side of the spine.

Function of the Kidneys

They eliminate excess water, salts, and waste products of protein metabolism from the blood while returning nutrients and chemicals to it. They carry waste products from the blood into the urine, which drains through the ureters into the bladder.

Parts of the Kidney

  • Cortex
  • Medulla (Malpighian pyramids)
  • Renal sinus

Nephron: The minimal functional unit of the kidney.

Other Features of the Kidney

  • Irrigation: Renal arteries and veins.

Adrenal Gland

Located on the superomedial sides of the kidneys. Surrounded by connective tissue and perirenal fat. Enclosed by the renal fascia, which is fixed to the diaphragmatic pillars.

Parts of the Adrenal Gland

  • Left adrenal gland: Related to the spleen, stomach, pancreas, and left crus of the diaphragm.
  • Right adrenal gland: In front of the diaphragm, it makes contact with the inferior vena cava and liver.

Each gland has:

  • Adrenal cortex: Zona glomerulosa, Zona fasciculata, Zona reticularis.
  • Medulla

Other Features of the Adrenal Gland

  • Irrigation: Adrenal arteries and veins.

Ureter

A urinary tract that carries urine from the kidney to the bladder. On the way from the ureter into the bladder is a “valve” that prevents urine from backing up into the kidneys. Their intertwined muscle fibers are arranged in three layers: intermediate, external, and internal.

In men, the urethra has a length of about 20 inches and opens to the outside at the urethral meatus of the glans. The male urethra has different sections:

Sections of the Male Urethra

  • Prostatic
  • Membranous
  • Spongy

Other Features of the Ureter

  • Innervation: Iliac nodes, pudendal nerve.
  • Irrigation: Prostatic artery, vaginal artery.

Bladder

A musculo-membranous hollow organ that is part of the urinary tract. It receives urine from the ureters and ejects it through the urethra to the outside of the body during urination. When full, it has a spherical shape, and when empty, it resembles a tetrahedron with:

Parts of the Bladder

  • Vertex
  • Body
  • Fundus

The interior of the bladder reveals the bladder mucosa, the ureteral orifice, and the bladder neck (the junction with the urethra). These three points define the trigone, which is a fixed and non-distensible portion of the organ.

Layers of the Bladder Wall

  • Serosa layer
  • Muscularis: Smooth muscle with three layers:
    • Superficial: Longitudinal muscle fibers.
    • Middle: Circular muscle fibers.
    • Deep: Longitudinal fibers. They form the detrusor muscle, which contracts and expels urine, opposing the sphincters of the urethra.
  • Mucous layer

Other Features of the Bladder

  • Vascularization: Internal iliac artery, superior and inferior vesical arteries, accompanying veins.
  • Innervation: Prostatic venous plexus in males and vaginal venous plexus in females.
  • Lymphatic drainage: External and internal iliac lymph nodes.