General Splanchnology

Introduction to Splanchnology

• Definition: Splanchnology is the branch of anatomy that focuses on the study of the internal organs (viscera) within the thoracic, abdominal, and pelvic cavities.
• Importance:
  • Vital for understanding the anatomy, physiology, and pathology of internal organs.
  • Essential for veterinary diagnostics, surgical procedures, and treatment planning.
  • Helps in understanding the interrelationships between different organ systems.

Boundaries of Body Cavities

• Thoracic Cavity:
  • Boundaries:
    • Superior: Thoracic inlet (opening at the top of the thorax).
    • Inferior: Diaphragm (muscle separating thorax from abdomen).
    • Lateral: Ribs and intercostal muscles.
    • Posterior: Thoracic vertebrae.
  • Contents:
    • Heart: Enclosed in the pericardial sac; consists of four chambers (right atrium, right ventricle, left atrium, left ventricle).
    • Lungs: Two lobes in the left lung and three lobes in the right lung; responsible for gas exchange.
    • Major Blood Vessels: Aorta, pulmonary arteries and veins, superior and inferior vena cava.
    • Other Structures: Trachea, esophagus, thymus gland, and nerves (e.g., phrenic and vagus nerves).
• Abdominal Cavity:
  • Boundaries:
    • Superior: Diaphragm.
    • Inferior: Pelvic inlet.
    • Anterior: Abdominal muscles.
    • Posterior: Lumbar vertebrae and psoas muscles.
  • Contents:
    • Digestive Organs: Stomach, small intestine (duodenum, jejunum, ileum), large intestine (cecum, colon, rectum).
    • Accessory Organs: Liver (produces bile), gallbladder (stores bile), pancreas (produces digestive enzymes and hormones).
    • Spleen: Involved in immune response and blood filtration.
    • Kidneys: Located retroperitoneally; responsible for urine production and regulation of electrolytes.
• Pelvic Cavity:
  • Boundaries:
    • Superior: Pelvic inlet.
    • Inferior: Pelvic floor.
    • Lateral: Pelvic bones.
    • Posterior: Sacrum and coccyx.
  • Contents:
    • Reproductive Organs: Ovaries, uterus, vagina in females; testes, prostate, and penis in males.
    • Urinary Bladder: Stores urine; can expand significantly.
    • Rectum: Terminal part of the large intestine; stores feces prior to excretion.

Topography of Organ Systems

Digestive System

• Mouth:
  • Components: Lips, cheeks, gums, hard and soft palates, tongue, and teeth.
  • Function: Initiates digestion through mechanical breakdown and saliva production.
• Esophagus:
  • Location: Muscular tube extending from the pharynx to the stomach.
  • Function: Transports food via peristalsis.
• Stomach:
  • Regions: Fundus, body, and pylorus; varies among species (e.g., monogastric vs. ruminant).
  • Function: Secretes gastric juices for digestion; ruminants have a complex stomach with multiple chambers (rumen, reticulum, omasum, abomasum).
• Intestines:
  • Small Intestine:
    • Sections: Duodenum (receives bile and pancreatic juices), jejunum, ileum (nutrient absorption).
  • Large Intestine:
    • Sections: Cecum (fermentation in herbivores), colon (water absorption), rectum (storage of feces).
• Accessory Organs:
  • Liver: Largest internal organ; processes nutrients, detoxifies substances, produces bile.
  • Pancreas: Exocrine function (produces digestive enzymes) and endocrine function (produces insulin and glucagon).

Respiratory System

• Nasal Cavity:
  • Function: Filters, warms, and humidifies air; contains olfactory receptors for smell.
• Larynx:
  • Function: Voice production; protects the trachea against food aspiration.
• Trachea:
  • Structure: Cartilaginous rings maintain openness; bifurcates into left and right bronchi.
• Lungs:
  • Structure: Composed of lobes (two in the left lung, three in the right); alveoli are the sites of gas exchange.
  • Function: Oxygenates blood and removes carbon dioxide.

Urinary System

• Kidneys:
  • Location: Retroperitoneal; bean-shaped organs.
  • Function: Filter blood, regulate electrolytes, produce urine.
• Ureters:
  • Function: Transport urine from kidneys to bladder via peristalsis.
• Urinary Bladder:
  • Structure: Muscular sac that stores urine; expands as it fills.
• Urethra:
  • Function: Conducts urine out of the body; length varies between sexes.

Endocrine System

• Glands:
  • Pituitary Gland: Master gland controlling other endocrine glands.
  • Thyroid Gland: Regulates metabolism and growth.
  • Adrenal Glands: Produce hormones related to stress response (cortisol, adrenaline).
  • Pancreas: Regulates blood sugar levels through insulin and glucagon.

Male Reproductive System

• Testes:
  • Function: Produce sperm and testosterone; located in the scrotum in most mammals.
• Epididymis:
  • Function: Stores and matures sperm.
• Vas Deferens:
  • Function: Transports sperm to the urethra.
• Accessory Glands:
  • Prostate and Seminal Vesicles: Produce seminal fluid that nourishes and transports sperm.

Female Reproductive System

• Ovaries:
  • Function: Produce eggs (ova) and hormones (estrogen, progesterone).
• Fallopian Tubes:
  • Function: Transport eggs from ovaries to the uterus; site of fertilization.
• Uterus:
  • Function: Site of fetal development; consists of three layers (endometrium, myometrium, perimetrium).
• Vagina:
  • Function: Birth canal and organ for copulation; connects uterus to the external environment

Point wise shorts notes of Introduction to Splanchnology

• Definition: Study of internal organs (viscera) in body cavities.
• Importance: Essential for understanding anatomy, physiology, and pathology of organs.

Boundaries of Body Cavities

• Thoracic Cavity:
  • Boundaries: thoracic inlet, diaphragm, ribs, vertebrae.
  • Contents: heart, lungs, major blood vessels, trachea, esophagus.
• Abdominal Cavity:
  • Boundaries: diaphragm, pelvic inlet, abdominal muscles, vertebrae.
  • Contents: digestive organs, liver, gallbladder, pancreas, spleen, kidneys.
• Pelvic Cavity:
  • Boundaries: pelvic inlet, pelvic floor, pelvic bones, sacrum, coccyx.
  • Contents: reproductive organs, urinary bladder, rectum.

Topography of Organ Systems

Digestive System

• Mouth: lips, cheeks, gums, palate, tongue, teeth.
• Esophagus: transports food to stomach.
• Stomach: varies in structure among species.
• Intestines: small (duodenum, jejunum, ileum) and large (cecum, colon, rectum).
• Accessory Organs: liver, pancreas.

Respiratory System

• Nasal Cavity: filters, warms, humidifies air.
• Larynx: voice production, protects trachea.
• Trachea: conducts air to lungs.
• Lungs: alveoli for gas exchange.

Urinary System

• Kidneys: filter blood, produce urine.
• Ureters: transport urine to bladder.
• Urinary Bladder: stores urine.
• Urethra: conducts urine out of body.

Endocrine System

• Glands: pituitary, thyroid, adrenal, pancreas.
• Function: regulate metabolism, growth, reproduction via hormones.

Reproductive Systems

• Male: testes, epididymis, vas deferens, accessory glands.
• Female: ovaries, fallopian tubes, uterus, vagina