The Abdominal Cavity Anatomical and Physiological Relationships Clinical

The Abdominal Cavity Anatomical and Physiological Relationships Clinical Practicum 1 Lecture One Holdorf

The ability of the sonographer to understand anatomy as it relates to the cross-sectional, coronal, oblique, and sagittal projections is critical in performing a quality sonogram.

The sonographer must have a thorough understanding of anatomy as it relates to the anteroposterior relationships, as well as the variations in sectional anatomy

u Gross anatomy studies the body by dissection of tissues. u Histology studies parts of the tissues under the microscope.

u Embryology studies the development before birth. u Pathology is the study of the disease process.

u Within the human body, the basic unit of structure and function is a microscopic part called a cell. u All cells have tiny parts called organelles that carry on specific activities.

u These organelles are composed of aggregates of large molecules (proteins, carbohydrates, lipids, and nucleic acids). u Cells are organized into layers or masses that have common functions, known as a tissue.

u Groups of different tissues form organs (complex structures with specialized functions). u. A group of organs is arranged into organ systems. u Organ systems make up an organism.

u u u A coordinated group of organs are arranged into organ or body systems. For example the digestive system consists of the mouth, esophagus, stomach, intestines, liver, gallbladder, and pancreas. Body systems make up the total part or organism; that is, the human body itself.

Metabolism u All of the physical and chemical changes that occur within the body are referred to as metabolism. u The metabolic process is essential to digestion, growth, and repair of the body, and conversion of food energy into forms useful to the body.

Homeostasis u Homeostasis is the ability to maintain a steady and stable internal environment. u Stressful stimuli, stressors, disrupt homeostasis.

Vital signs are medical measurements used to ascertain how the body is functioning. These vital signs include measuring body temperature and blood pressure and observing rates and types of pulse and breathing movements.

Anatomic Directions The anatomic position implies that the body is standing erect, the eyes are looking forward, and the arms are at the sides with the palms and toes directed forward.

Superior/inferior u The top of the head is the most superior point of the body. u The inferior point of the body is the bottom of the feet. All anatomic structures are designated relative to these two terms.

u The liver is considered to be superior to the bladder because the liver is closer to the head. u The gallbladder is inferior to the diaphragm because it is closer to the feet.

u Others terms that are interchanged with superior are cephalic and cranial (toward the head). u Caudal (toward the tail) is sometimes used instead of inferior

Anterior/posterior The front (belly) surface of the body is anterior, or ventral. The back surface of the body is posterior, or dorsal. This concept is very important to the sonographer and their understanding of sectional anatomy.

Medial/lateral u The body axis is an imaginary line from the center of the top of the head to the groin. u Medial is described as the superior– inferior body axis as it goes right through the midline of the body. .

u Structures are said to be medial if they are closer to the midline of the body than to another structure (i. e. , the hepatic artery is medial to the common duct).

u The structure is lateral if it is toward the side of the body. u The adnexa are lateral to the uterus

Proximal/distal u When a structure is closer to the body midline or point of attachment to the trunk, it is described as proximal. u Distal means father from the midline or point of attachment to the trunk

Superficial/deep u Structures located toward the surface of the body are superficial u Structures located farther inward (away from the body surface) are deep.

Planes or Body Sections The body is observed by the sonographer in several different planes: transverse, sagittal, and coronal.

Transverse: The transverse plane is horizontal to the body. This plane divides the body or any of its parts into upper and lower portions

Sagittal: The sagittal plane is a lengthwise plane running from front to back. It divides the body or any of its parts into right and left sides, or two equal halves. This is also known as the midsagittal plane.

Coronal: The coronal plane is a lengthwise plane running from side to side, dividing the body into anterior and posterior portions.

Abdominal Quadrants and Regions In order to identify specific abdominal structures or refer to an area of pain, the abdomen may be divided into four quadrants or abdominal regions.

The quadrant is determined by a midsagittal and a transverse plane that pass through the umbilicus. The abdominopelvic cavity is divided into four quadrants: u u the right upper quadrant (RUQ), left upper quadrant (LUQ), right lower quadrant (RLQ), and left lower quadrant (LLQ).

u The abdomen is commonly divided into nine regions by two vertical and two horizontal lines. u The surface landmarks of the anterior abdominal wall help to define the specific abdominal regions.

u Each vertical line passes through the midinguinal point; that is, the point that lies on the inguinal ligament halfway between the pubic symphysis and anterior superior iliac spine.

u u u The upper horizontal line, referred to as the subcostal plane, joins the lowest point of the costal margin on each side of the body. The lowest horizontal line, the intertubercular plane, joins the tubercles on the iliac crests. The transpyloric plane is a horizontal plane that passes through the pylorus, duodenal junction, neck of the pancreas, and hilum of the kidneys.

The nine abdominal regions include the following: 1. upper abdomenright hypochondrium. 2. epigastrium. 3. left hypochondrium. 4. middle abdomen/right lumbar. 5. umbilical. 6. left lumbar. 7. lower abdomen/right iliac fossa. 8. hypogastrium. 9. left iliac fossa.

Body Cavities u Within the human body there are many body cavities. u These body cavities contain the internal organs, or viscera.

u The two principal body cavities are the dorsal cavity and the ventral cavity. u The bony dorsal cavity may be subdivided into the cranial cavity, which holds the brain, and the vertebral or spinal canal, which contains the spinal cord

u The ventral cavity is located near the anterior body surface and is subdivided into the thoracic cavity and the abdominal cavity. u The thoracic and abdominopelvic cavities are separated by a broad muscle, the diaphragm, which forms the floor of the thoracic cavity

u Divisions of the thoracic cavity are the pleural sacs, each containing a lung, with the mediastinum between them. u Within the mediastinum lies the heart, thymus gland, part of the esophagus, and trachea. u The heart is surrounded by another cavity called the pericardial sac.

The Abdominal Cavity The abdominal cavity (excluding the retroperitoneum and the pelvis) is bounded superiorly by the diaphragm; anteriorly by the abdominal wall muscles; posteriorly by the vertebral column, ribs, and iliac fossa; and inferiorly by the pelvis.

Abdominal Viscera The abdominal visceral organs: liver, gallbladder, spleen, pancreas, kidneys, great vessels, stomach, and most of the small and large intestines.

Other Abdominal Structures Diaphragm u The diaphragm is a dome-shaped muscle that separates the thorax from the abdominal cavity. u The right crus arises from the sides of the bodies of the first three lumbar vertebrae u The left crus arises from the sides of the bodies of the first two lumbar vertebrae.

Abdominal Wall u The abdominal wall is superiorly formed by the diaphragm. u It is inferiorly continuous with the pelvic cavity through the pelvic inlet.

u Anteriorly the wall is formed above by the lower part of the thoracic cage and below by several layers of muscles: the rectus abdominis external oblique internal oblique transversus abdominis.

u u u The linea alba is a fibrous band that stretches from the xiphoid to the symphysis pubis. Posteriorly the abdominal wall is formed in the midline by five lumbar vertebrae and their disks. Laterally it is formed by the twelfth ribs, upper part of the bony pelvis, psoas muscles, quadratus lumborum muscles, and the aponeuroses of origin of the transversus abdominis muscles.

Superficial Inguinal Ring u The superficial inguinal ring is a triangular opening in the external oblique aponeurosis and lies superior and medial to the pubic tubercle. u The spermatic cord or the round ligament of the uterus passes through this opening.

Inguinal Ligament u The inguinal ligament is formed between the anterior superior iliac spine and the pubic tubercle, where the lower border of the aponeurosis is folded backward on itself. u The lateral part of the posterior edge of the inguinal ligament gives origin to part of the internal oblique and transverse abdominal muscles.

The Pelvic Cavity Pelvis major (false pelvis): Part of the abdominal cavity proper; lies between the iliac fossae, superior to the pelvic brim. Pelvis minor (true pelvis): Contains the pelvic cavity; inferior to the brim of the pelvis.

Perineum The true pelvis is subdivided by the pelvic diaphragm into the main pelvic cavity and the perineum.

Abdominopelvic Membranes and Ligaments Peritoneum The Peritoneum is the serous membrane lining the walls of the abdominal cavity; it covers the abdominal viscera. It is formed by a single layer of cells called the mesothelium, which rests on a thin layer of connective tissue.

The peritoneum is divided into two layers: parietal peritoneum is the portion that lines the abdominal wall but does not cover a viscus; the visceral peritoneum is the portion that covers an organ. The peritoneal cavity is the potential space between the parietal and visceral peritoneum.

Accumulation of fluid is known as ascites. The peritoneal cavity forms a completely closed sac in the male; in the female there is a communication with the retroperitoneal cavity through the uterine tubes, uterus, and vagina.

Retroperitoneal organs and vascular structures remain posterior to the cavity and are covered anteriorly with peritoneum: urinary system, aorta, inferior vena cava, colon, pancreas, uterus, and bladder.

Mesentery u The mesentery is a two-layered fold of peritoneum that attaches part of the intestines to the posterior abdominal wall and includes the mesentery of the small intestine, the transverse mesocolon, and the sigmoid mesocolon.

Omentum Two-layered fold of peritoneum that attaches the stomach to another viscus organ. u Greater omentum: This is attached to the greater curvature of the stomach and hangs down like an apron in the space between the small intestine and anterior abdominal wall. The greater omentum is folded back on itself and is attached to the inferior border of the transverse colon.

u Lesser omentum: This slings the lesser curvature of the stomach to the undersurface of the liver. The gastrosplenic omentum ligament connects the stomach to the spleen

Ligament u Peritoneal ligaments are two-layered folds of peritoneum that attach the less mobile solid viscera to the abdominal walls. u u The liver is attached by the falciform ligament to the anterior abdominal wall and to the undersurface of the diaphragm The ligamentum teres lies in the free borders of this ligament

Potential Spaces in the Body Subphrenic Spaces u The right and left anterior subphrenic spaces lie between the diaphragm and the liver, one on each side of the falciform ligament. u The right posterior subphrenic space lies between the right lobe of the liver, the right kidney, and the right colic flexure, called Morison’s pouch

Paracolic Gutters The arrangement of the ascending and descending colon, the attachments of the transverse mesocolon, and the mesentery of the small intestine to the posterior abdominal wall result in the formation of four paracolic gutters.

u The clinical significance of these gutters is their ability to conduct fluid materials (abscess, ascites, blood, pus, bile, or metastases) from one part of the body to another.

u The gutters are on the lateral and medial sides of the ascending and descending colon. u The right medial paracolic gutter is closed off from the pelvic cavity inferiorly by the mesentery of the small intestine.

u The right lateral paracolic gutter communicates with the right posterior subphrenic space. u The left lateral gutter is separated from the area around the spleen by the phrenicocolic ligament.

Inguinal Canal u The inguinal canal is an oblique passage through the lower part of the anterior abdominal wall. u u In the male, it allows structures to pass to and from the testes to the abdomen. In the female, it permits the passage of the round ligament of the uterus from the uterus to the labium majus.

Retroperitoneal Spaces The anterior pararenal space: Located between the anterior surface of the renal fascia (Gerota’s fascia) and the posterior area of the peritoneum (contents: ascending and descending colon, pancreas, and duodenum).

The posterior pararenal space: Found between the posterior renal fascia and the muscles of the posterior abdominal wall (contents: fat and vessels).

u The perirenal space: Located directly around the kidney and is completely enclosed by renal fascia (contents: kidneys, adrenal glands, lymph nodes, blood vessels, and perirenal fat).