Gastrointestinal Tract Flashcards
Roughly define where the abdomen is situated.
Between the thorax and the pelvis.
Which four structures provide attachment points for the anterior abdominal wall muscles?
The iliac crest, the anterior superior iliac spine (ASIS), the pubic tubercle and the pubic crest.
How many flat and vertical muscles are there in the anterior of the abdomen?
3 flat muscles.
2 vertical muscles (paired).
The external oblique muscle, internal oblique muscle and transversus abdominus muscle have distinguishable lateral and medial components. Explain.
The EO, IO and TA muscles are fleshy laterally and aponeurosis medially. The aponeurosis of each interdigitate to form the linea alba at the midline.
What is the fiber direction of the external oblique muscle?
Inferomedial “front pocket” (forwards, downwards).
Describe the attachment points of the external oblique muscles.
Superiorly, the EO muscle attaches to the ribs, overlapping the costal margin.
Medially, the EO muscle attaches to the linea alba.
Inferiorly, the EO muscle attaches to the iliac crest posteriorly, then laterally, then to the ASIS, before jumping and attaching to the pubic crest and pubic tubercle. (i.e. central part has no attachments).
Posteriorly, the EO muscle is associated with posterior abdominal wall muscles.
Describe the attachment points of the internal oblique muscle.
Superiorly, the IO muscle attaches to the costal margin.
Inferiorly, the IO muscle arises from the lateral part of the inguinal ligament (2/3) before arching up and down to insert into the pubic crest via a conjoint tendon.
Posteriorly, the IO muscle is associated with posterior abdominal wall muscles.
What is the fiber direction of the internal oblique muscle?
The majority of the IO muscle has superomedial direction (upwards and medial). However, the lowermost fibers do not. They arch up, over and downward to insert into the pubic crest.
Define and describe the inguinal ligament.
The inguinal ligament is the free, inferior border of the external oblique muscle. It is an undercurving, thickened, fibrous band that extends from the anterior superior iliac spine (ASIS) to the pubic tubercle.
Describe the attachment points of the transversus abdominus.
Superiorly, the TA muscle attaches to the costal margin.
The lowermost fibers arise from the lateral part (1/3) of the inguinal ligament and arch up and down to insert into the pubic crest via a conjoint tendon.
Posteriorly, the TA muscle is associated with posterior abdominal muscles.
Describe the fiber direction of the transversus abdominis muscle.
The majority of the TA muscle has transverse (horizontal) fiber direction. However, the lowermost fibers do not. They arch up, over and downward to insert into the pubic crest.
What are the two vertically orientated muscles of the anterior abdominal wall?
The rectus abdominis muscles and the pyramidalis muscles.
Briefly discuss the pyramidalis muscles of the anterior abdominal wall.
The pyramidalis muscles are very small muscles (not present in everyone) which attach to the pubic crest. The muscles do not have a major role.
Discuss the location, features and covering of the rectus abdominus muscles.
The rectus abdominus muscles are paired muscles situated on either side of the linea alba. They are the principle vertical muscles of the anterior abdominal wall. The rectus abdominus muscles arise from the pubic bones and attach to the rib cage. The muscles are intersected by tendons. The rectus abdominus muscles are enclosed in the rectus sheath (an envelope of fascia).
What is the rectus sheath formed by? What does the rectus sheath enclose?
The rectus sheath is formed by the aponeuroses of the external oblique, internal oblique and transversus abdominus muscles. The rectus sheath is a fibrous compartment that encloses the rectus abdominus muscles.
