Using the Sectra table, you will identify structures of the abdomen, inguinal region, and scrotum. Bolded terms are in the objectives for this lab.
The Abdominal Region I
“The abdomen is the portion of the trunk between the thorax and the pelvis. Superiorly, the abdominal cavity is physically divided from the thoracic cavity by the diaphragm. Inferiorly, the abdominal cavity is continuous with the pelvic cavity, and thus, this region is commonly referred to as the abdominopelvic cavity. The abdominal organs (viscera) are not bilaterally symmetrical. Therefore, it is worth noting that use of the words “right” and “left” in names and instructions refers to the right and left sides of the cadaver in the anatomical position.” – Grant’s Dissector 16th ed.
Anterior abdominal wall
As you identify and dissect muscles, you should review their origin, insertion, innervation, and action(s). As you identify and dissect neurovascular structures, you should review their pathways.
If you are having trouble highlighting narrow structures (arteries, veins, nerves), you can search for them by selecting the Anatomy tab, typing the name of the structure in the search box, and selecting the sun icon next to the listed structure. You can dissect these structures by selecting the eye icon.
As you highlight a structure, note that the structure will also be highlighted in the multiplanar reconstructed (MPR), or cross-sectional images in the leftmost pane. All structures should be identified on the MPR images. Using three fingers, scroll through the MPR images to understand the three-dimensional relationships between different structures as you work though the lab. Structures that are difficult to identify in the MPR images will have additional links to assist you.
Begin your dissection (select this button at any time to start over):
- Using the top MPR image, identify the skin and the Camper’s fasica (fatty layer). The Scarpa’s fascia (membranous layer) will not be identifiable
- Using the top MPR image, identify the three layers of the lateral abdominal muscles on the left and right sides: the external oblique, the internal oblique, and the transversus abdominis
- Medially, identify the rectus abdominis muscle on the left and right sides
- Identify the linea alba medial to the left and right rectus abdominis muscles
- Dissect the abdominal muscles and identify the aponeurosis of the transversus abdominis (partially visible on the model)
The linea alba is formed from the fusion of the aponeuroses of the abdominal muscles, which are for the most part not visible on the model. Review the figure below to understand which parts of the aponeuroses of the external oblique, internal oblique, and transversus abdominis form the anterior rectus sheath and posterior rectus sheath, and how this relationship changes superior and inferior to the arcuate line
The iliohypogastric nerve is not visible in the anterior abdominal wall on the model.
Q1: Which abdominal muscles does the ilioinguinal nerve pierce as it travels anteriorly? (answer)
- Identify the inferior epigastric artery and inferior epigastric vein (MPR)
Q2: Where is the linea semilunaris, and how does it contribute to Hesselbach’s triangle? (answer)
Inguinal region
The layers of the spermatic cord and scrotum are derived from the same embryological structures that form the abdominal wall. As you identify the structures of the inguinal region, review which tissues are linked in this way.
The right spermatic cord and testes are missing (this is a feature of this individual cadaver, and not an error). Don’t forget that the structures in this region are normally bilateral.
- Identify the inguinal ligament and the cremaster muscle (MPR)
- identify and dissect the spermatic cord
- Identify the ductus deferens (vas deferens), the pampiniform plexus, testicular artery, and genitofemoral nerve within the spermatic cord (note that the genitofemoral nerve and testicular artery are truncated on the model distal to the cremaster muscle)
- Identify the testis (MPR)
Q3: What structures form the superficial inguinal ring? What structures form the deep inguinal ring? What structures travel through the inguinal canal? (answer)
The following structures cannot be identified on the model. Use the diagrams below to understand their relative position:
- External and internal spermatic fascia
- Ilioinguinal nerve and artery of the vas deferens
- Dartos fascia and muscle
- Scrotal ligament (remnant of the gubernaculum) and scrotal septum
- Tunica vaginalis (visceral and parietal layers)
- Tunica albuginea
- Epididymis (tail, body, head)
- Seminiferous tubules
Use the following view to examine the female inguinal region:
- Identify the round ligament of the uterus
- Identify the labium majus
Q4: What male structure is developmentally equivalent to the round ligament of the uterus? (answer)
Identify structures of the anterior abdominal wall on the female pelvic section. For example, you can identify the tendinous intersections of the rectus abdominis muscle on this model, but not the male model.
Abdominal Viscera
Use the following view to examine the abdominal viscera:
- Identify the round ligament of the liver travelling anterior to the abdominal viscera (MPR)
- Identify and dissect the jejunum and ilium of the small intestine (MPR)
- Identify and dissect the parts of the large intestine: cecum, ascending colon, transverse colon, descending colon, and sigmoid colon (the appendix is not present on the model)
- Identify the rectum. You many need to rotate the model anteriorly to view it (MPR)
- Identify the pancreas and duodenum (MPR)
The mesenteries are not visible on the model. Use the diagrams below to identify the following structures:
- parietal peritoneum and visceral peritoneum,
- greater omentum and lesser omentum (hepatogastric and hepatoduodenal ligaments), and lesser peritoneal sac (omental bursa)
- mesentery proper (and root of the mesentery)
- mesoappendix, transverse mesocolon, sigmoid mesocolon
- Dissect the diaphragm and identify the liver
- Identify the falciform ligament. Note the position of the round and falciform ligaments in relation to the liver (MPR)
- Identify the gallbladder on the inferior surface of the liver
- Identify the stomach
Q5: What fetal structure becomes the round ligament of the liver? (answer)
End of Sectra activity
Answers to activity questions
Below are answers to questions asked during the activity. Clicking the ‘back to lab’ link below each answer will take you back to the question (you may need to scroll up a little to view the question again).
Q1: Which abdominal muscles does the ilioinguinal nerve pierce as it travels anteriorly?
- The ilioinguinal nerve pierces the transversus abdominis near the iliac crest, then the internal oblique muslce before passing through the superficial inguinal ring. It does not pierce the external oblique muscle
Q2: Where is the linea semilunaris, and how does it contribute to Hesselbach’s triangle?
- The linea semilunaris is formed by the aponeurosis of the external oblique, internal oblique, and transversus abdominis lateral to the rectus abdominis. It forms the medial border of Hasselback’s triangle (inguinal triangle)
Q3: What structures form the superficial inguinal ring? What structures form the deep inguinal ring? What structures travel through the inguinal canal?
- The superficial inguinal ring is formed by the aponeurosis of the external oblique muscle and the inguinal ligament
- The deep inguinal ring is formed by the transversalis fascia
- Structures that pass through the inguinal canal: the ilioinguinal nerve, the genital branch of the genitofemoral nerve, and the spermatic cord (men) or the round ligament (women)
Q4: What male structure is developmentally equivalent to the round ligament of the uterus?
- The round ligament of the uterus and the scrotal ligament have the same embryological origin (the gubernaculum)
Q5: What fetal structure becomes the round ligament of the liver?
- The round ligament of the liver (ligamentum teres hepatis) is a remnant of the umbilical vein