Heart, Kidney, and Urinary System Anatomy
Heart
Structure
The heart is a hollow, muscular organ responsible for pumping blood throughout the body. It is divided into four chambers: two atria (upper chambers) and two ventricles (lower chambers). The heart is enveloped by a protective membrane called the pericardium.
Layers of the Heart (from inside out):
- Endocardium
- Myocardium
- Epicardium
Chambers of the Heart:
- Top: Right Atrium, Left Atrium
- Bottom: Right Ventricle, Left Ventricle
The atria are separated by the interatrial septum, and the ventricles are separated by the interventricular septum. These walls form a continuous membranous-muscular structure that divides the heart into two distinct halves.
Innervation
Extrinsic Innervation: The heart’s rate and contractility are modulated by the autonomic nervous system, which adjusts heart function based on the body’s needs.
Intrinsic Conduction System: This specialized system within the heart coordinates the heartbeat. It consists of:
- Sinoatrial (SA) Node
- Atrioventricular (AV) Node
- Bundle of His
- Purkinje Fibers
Vascularization
Arteries:
The coronary arteries, branching from the ascending aorta, supply oxygenated blood to the heart muscle. The two main coronary arteries are the right and left coronary arteries.
- Right Coronary Artery: Runs along the right atrioventricular (AV) groove, supplying blood to the right side and back of the heart.
- Left Coronary Artery: Divides into two branches:
- Anterior Interventricular Artery (Left Anterior Descending): Travels down the anterior interventricular sulcus.
- Circumflex Artery: Courses along the left AV groove, encircling the heart and connecting with the right coronary artery.
Veins:
Venous blood from the heart is collected by veins that run alongside the arteries. Most of these veins drain into the coronary sinus, located in the posterior AV groove. The coronary sinus empties into the right atrium.
Kidney
Structure and Function
The kidneys are bean-shaped excretory organs located on either side of the spine in the posterior abdominal wall. Their primary functions include:
- Filtering waste products from the blood and producing urine.
- Regulating blood pressure, electrolyte balance, and red blood cell production.
Parts of the Kidney:
- Cortex
- Medulla (containing renal pyramids)
- Renal Sinus
Nephron: The functional unit of the kidney, responsible for filtering blood and forming urine.
Vascularization
The kidneys are supplied by the renal arteries and drained by the renal veins.
Adrenal Glands
Location and Structure
The adrenal glands are located on the superomedial aspect of each kidney. They are surrounded by connective tissue and perirenal fat and enclosed by the renal fascia.
Each adrenal gland consists of:
- Adrenal Cortex:
- Zona Glomerulosa
- Zona Fasciculata
- Zona Reticularis
- Adrenal Medulla
Vascularization
The adrenal glands are supplied by the adrenal arteries and drained by the adrenal veins.
Ureter
Structure and Function
The ureters are tubes that carry urine from the kidneys to the bladder. They have a valve-like mechanism to prevent urine backflow.
Layers of the Ureter Wall:
- Outer Layer
- Middle Layer
- Inner Layer
Male Urethra
The male urethra is approximately 20 inches long and has several sections:
- Prostatic Urethra
- Membranous Urethra
- Spongy Urethra
Bladder
Structure and Function
The bladder is a hollow, muscular organ that stores urine received from the ureters and expels it through the urethra during urination.
Parts of the Bladder:
- Vertex
- Body
- Fundus
Trigone: A triangular area in the bladder formed by the ureteral orifices and the bladder neck.
Layers of the Bladder Wall:
- Serosa
- Muscularis (Detrusor Muscle):
- Superficial Layer (longitudinal muscle fibers)
- Middle Layer (circular muscle fibers)
- Deep Layer (longitudinal muscle fibers)
- Mucosa
Vascularization
The bladder is supplied by the superior and inferior vesical arteries, branches of the internal iliac artery.
Innervation
The bladder is innervated by nerves from the prostatic venous plexus in males and the vaginal venous plexus in females.
Lymphatic Drainage
Lymph from the bladder drains into the external and internal iliac lymph nodes.