Anatomy for Surgery II: Regions by Specialty

This is Unit Four of Tech in Surgery Prep. Unit Three ended with a surgeon's single sentence turned into a picture of the case. This unit adds the regions those pictures are made of: the chest, the abdomen, the great vessels, the nervous system and bone. Carry one idea through this lecture. The textbook's anatomy is the map, not the territory. Real patients vary, and the surgeon identifies each structure before dividing it. A worked example near the end shows how the map is used, and where it stops. By the end you will be able to describe the chest and the airway. To trace the digestive tract and its accessory organs. To describe the urinary organs, the main circulation and the central nervous system. And to name the parts of a long bone and picture the anatomy of a case before it starts.

Three entries on the chest: the cavity, the lungs inside it, and the airway that anesthesia secures.

The upper ventral cavity.

TSC 076 The Thoracic Cavity

The thoracic cavity is the upper part of the ventral cavity, enclosed by the rib cage and floored by the diaphragm. It holds the two lungs, each in its own pleural cavity, with the mediastinum and the heart between them. Opening the chest changes how the lungs work, so anesthesia and the surgeon plan chest cases closely together.

Three lobes and two.

TSC 077 The Lungs and Pleura

The lungs are joined to the trachea by the right and left bronchi and rest on the diaphragm. The right lung has three lobes, superior, middle and inferior; the left has two, separated by fissures. Removing a single lobe is a lobectomy.

The path air takes.

TSC 078 The Airway

Air reaches the lungs through the conducting zone: the nose, pharynx, larynx, trachea and bronchi. The trachea is held open by C-shaped rings of cartilage, and the zone warms, humidifies and filters air without exchanging gases. Under general anesthesia, the anesthesia provider secures this airway with a breathing tube or other device.

Six entries on the digestive organs, from the mouth to the anus, with the organs that serve the canal and the membrane over them.

A tube and its helpers.

TSC 079 The Digestive Tract Overview

The digestive system has a continuous tube, the alimentary canal, and accessory organs. The canal runs from the mouth through the pharynx and esophagus to the stomach, which churns and mixes; then the small intestine, where most digestion and absorption happen; then the large intestine to the anus. The accessory organs include the teeth, tongue and salivary glands, and the liver, gallbladder and pancreas. The canal's wall has four layers almost everywhere: mucosa, submucosa, muscularis and serosa. Each behaves differently when bowel is opened or sewn, which shapes the instruments and suture chosen.

Four regions of the stomach.

TSC 080 The Stomach

The stomach has four regions: the cardia, where the esophagus enters; the fundus; the body; and the pylorus, which ends at the pyloric sphincter opening into the small intestine. Folds of peritoneum, the lesser and greater omentum, hold it in place and carry vessels the surgeon must respect.

Following the bowel.

TSC 081 The Small and Large Intestines

The small intestine has three parts. The duodenum, the shortest, begins at the pyloric sphincter and wraps around the head of the pancreas. The jejunum follows, then the ileum, the longest, which joins the large intestine at the ileocecal valve. The large intestine begins at the cecum, with the appendix attached, and continues as the ascending, transverse, descending and sigmoid colon, then the rectum and anal canal. Opening the bowel brings its contents and bacteria into the field, which changes how the field is managed.

A small tube with big consequences.

TSC 082 The Appendix

The appendix, the vermiform appendix, is a winding tube attached to the cecum, where the ileum meets the large intestine through the ileocecal valve. Because it opens into the bowel, removing it means handling bowel contents, a point unit twenty-four takes up with wound classes.

Three accessory organs.

TSC 083 Liver, Gallbladder and Pancreas

The liver, gallbladder and pancreas deliver their secretions into the small intestine. The liver is the body's largest gland, makes bile, and is highly vascular. The gallbladder, a small sac under the liver's right lobe, concentrates and stores bile until a meal. The pancreas lies behind the stomach, in the retroperitoneum, with its head inside the curve of the duodenum, and it both secretes digestive enzymes and releases hormones into the blood. Because the liver is so rich in blood, a case near it may bleed, so expect more sponges, suction and hemostatic supplies.

The abdominal lining.

TSC 084 The Peritoneum

The peritoneum is the serous membrane of the abdominal cavity, parietal on the wall and visceral on the organs. Its folds hold organs to the wall and carry their vessels, and the greater omentum drapes like an apron over the bowel. Organs behind it, such as the kidneys, are retroperitoneal.

Six entries on the urinary organs, the main circulatory pathways, and the brain and spinal cord.

Two organs behind the peritoneum.

TSC 085 The Kidneys

The kidneys lie behind the peritoneum on the back wall of the abdomen. They receive about a quarter of the heart's output at rest, and each drains urine into a ureter. Their position behind the peritoneum is why some kidney operations use a side-lying position rather than a front approach.

Urine's path out.

TSC 086 Ureters, Bladder, Urethra

Urine runs from each kidney down a ureter to the bladder, and leaves through the urethra. The kidneys and ureters lie entirely behind the peritoneum, and the bladder has a peritoneal covering only over its dome. Each ureter is a thin tube about a foot long, running down the back of the abdomen.

Two circuits.

TSC 087 Major Circulatory Pathways

Blood circulates in the pulmonary circuit through the lungs and the systemic circuit through the rest of the body. Oxygenated blood leaves the left ventricle through the aorta; large trunks branch from it, such as the celiac trunk to the stomach, liver and spleen region; arteries end in capillaries; and veins return the blood. The hepatic portal system carries blood from the digestive organs to the liver first. A vessel named for an organ supplies it, and controlling that vessel is often a key step in removing the organ.

The body's largest artery.

TSC 088 The Aorta and Its Branches

The aorta rises from the left ventricle, arches, and descends as the thoracic, then the abdominal, aorta. The abdominal aorta gives off branches including the renal arteries, then divides low in the abdomen into the two common iliac arteries. Aortic surgery works on the largest artery, so vascular clamps are prepared before anyone needs them.

Three coverings of the brain.

TSC 089 The Brain and Its Coverings

The brain is covered by three membranes, the meninges. The tough dura mater lies against the skull, the pia mater lies on the brain, and the arachnoid lies between. The dura also encloses the spinal cord, so the same layers are met in spine surgery.

The cord inside the spine.

TSC 090 The Spinal Cord

The spinal cord and brain form the central nervous system, and the cord runs in the spinal cavity of the vertebral column. The cranial and spinal cavities are continuous, and the dura encloses both. Spine surgery is usually done prone, a position whose risks unit fifteen covers.

Five entries on bone, burns and the diaphragm, then two worked examples. The opening idea is paid off at the first.

The parts of a long bone.

TSC 091 Parts of a Long Bone

A long bone has a shaft, the diaphysis, and a wider end on each side, the epiphysis. The shaft's hollow centre is the medullary cavity, lined by the endosteum. Each end is filled with spongy bone holding red marrow. Where the end meets the shaft is the metaphysis, which in growing bones holds the growth plate, and the outer surface is covered by the periosteum. The language of an orthopedic case maps onto these parts, so learning them makes an orthopedic preference card readable later.

Burns by depth.

TSC 092 Skin Injuries and Burns

Burns are classified by depth. A first-degree burn affects only the epidermis; a second-degree burn reaches part of the dermis; a third-degree burn destroys the epidermis and dermis, including nerve endings. Patients can be burned in surgery too, by energy devices or fire, which units nine and twenty-three teach how to prevent.

The muscle between two cavities.

TSC 093 The Diaphragm Between Two Cavities

The diaphragm is a dome-shaped muscle at the base of the lungs that separates the thoracic from the abdominopelvic cavity. It forms the floor of the chest, and the aorta passes through it into the abdomen. Because it borders both, work in the upper abdomen happens close to the chest.

Picturing a gallbladder case.

TSC 094 A Gallbladder Case in Anatomy

A worked example, constructed for this course, pays off the opening idea. A patient with gallstones is having the gallbladder removed. It lies in the right upper quadrant, under the liver's right lobe, so the work happens high on the right, under the ribs, near the diaphragm. It stores bile, so it is joined to the ducts toward the small intestine, and removing it means separating it from those and from its blood supply. The duodenum and pancreas lie nearby, under the peritoneum. At the field, suction, sponges and hemostatic supplies are ready because the liver bleeds; bile and stones must not spill; and the specimen goes to pathology. Real patients vary: the surgeon identifies each structure before dividing it, and the scrub person says when something looks different.

Picturing a bowel case.

TSC 095 A Bowel Case in Anatomy

A worked example, constructed for this course, follows removal of a diseased segment of sigmoid colon, which lies low on the patient's left. Like the rest of the canal, the colon has four wall layers, and joining two ends means bringing them together securely. The distal large intestine is supplied by an artery branching from the abdominal aorta and drained by the inferior mesenteric vein, and controlling them is a key step. Peritoneal folds carry those vessels, and the greater omentum may need moving aside. Opening the colon brings bacteria into the field, so the team plans to keep bowel instruments apart from closing instruments; the specimen goes to pathology. Every fact changed what the team prepared.

Look at what you can now do. You can describe the thoracic cavity, the lobes of each lung, and the airway that anesthesia secures. You can trace the digestive tract from mouth to anus, name its four wall layers and accessory organs, and explain the peritoneum. You can describe the kidneys and urinary tract, the two circulatory circuits and the aorta, and the coverings of the brain and spinal cord. And you can name the parts of a long bone, the depths of burns and the diaphragm's place, and picture a case's anatomy before it starts. Unit Five turns from the body to the medications used on the sterile field.