Anterior Abdominal Wall and GI Tract

1. Recall the regions and quadrants of the abdomen. 2. Describe the bones of the abdomen (lumbar vertebrae). 3. Describe the arrangement of the muscles that make up the anterior and lateral abdominal wall and describe their actions. 4. Distinguish the major segments of the gastrointestinal (GI) tract and recall the key features of each segment. 5. Describe the pattern of blood supply and venous drainage of the GI tract.

Describe the abdominal wall muscles

Flat muscles surrounding the abdominal cavity

What are the two functional groups of abdominal wall muscles?

anterolateral muscles, posterior muscles

What are the two key functions of the abdominal muscles?

protect the abdominal viscera, maintain posture and move the trunk

Name the groups of structures found in the abdominal cavity

abdominal wall, accessory organs of digestion, urinary system, arteries, veins and lymphatics

What are the accessory organs of digestion?

liver, gallbladder, pancreas

What makes up the urinary system?

kidneys, ureters

Whats a key role of the anterolateral abdominal muscles?

increase intra-abdominal pressure (e.g. for defecation and child-birth)

Whats a notable structural feature of the anterolateral abdominal muscles?

different fibre orientation

What are the two groups of anterolateral abdominal muscles?

Anterior (two on either side of midline), Lateral (three on either side of the midline)

What joins the two groups of anterolateral abdominal muscles?

rectus sheath

Label missing structures 1-3

linea alba, rectus fascia, rectus abominis

Label structures 4-6

transversus abdominis, internal oblique, external oblique

Is the external oblique muscle superficial or deep

most superficial muscle

define aponeurosis

sheet of pearly white fibrous tissue acting as a tendon in flat muscles and having a wide area of attachment

what structure is depicted in green?

external oblique muscle

Describe the main characteristics of the rectus abdominis muscle

long vertical muscles on either side of lines alba, inserted by tendinous intersections (ab lines), lies within the rectus sheath

What structure is depicted in green?

rectus abdominis muscle

Describe the fibre orientation of internal oblique muscle

fibres oriented perpendicular to EOM (medially and superiorly),

What does linea alba mean

white line

what structure is depicted in green

the internal oblique muscles

Is the transversus abdominis muscle superficial or deep?

its the deepest

What separates the transversus abdominis muscle from the abdominal cavity?

the transversalis fascia

describe the orientation of the transversus abdominis muscles fibres

horizontal

Describe how the aponeurosis of the internal oblique muscle divides

aponeurosis divides at rectus sheath anterior ½ forms anterior wall, posterior ½ forms posterior wall

describe the fibre orientation of the external oblique muscle

runs medially and inferiorly towards the midline

describe the external oblique muscles aponeurosis interactions with other structures in the abdominal wall

aponeurosis forms anterior wall of rectus sheath

What structure is depicted in green

transversus abdominis muscle

describe the interaction of the transversus abdominis muscle aponeurosis

aponeurosis forms the posterior wall of the rectus sheath

Define fascia

Thin casing of connective tissue that surrounds and holds structures

What is the rectus sheath formed by

The aponeurosis of the three lateral muscles enclosing the rectus abdominis

What forms the anterior wall of the rectus sheath

EOm + anterior ½ of IOm

What forms the posterior wall of the rectus sheath

the posterior ½ of IOm and TAm

What is the midline of the rectus sheath

linea alba

Label structures 1-4

external oblique m., internal oblique m., transverse abdominal m., rectus abdominal m.

Label structures 5-8

Anterior rectus sheath, posterior rectus sheath, peritoneum, transversals fascia

What is the role of the GI tract

processing food and eliminating waste (supported by the accessory organs of digestion)

List the journey of the GI tract from mouth to anus

thoracic and abdominal oesophagus, stomach, small intestine, large intestine, upper 1/3 rectum

Describe the blood supply to the GI tract

from the abdominal aorta: coeliac trunk + superior mesenteric artery (SMA) + inferior mesenteric artery (IMA)

Label structures 1-8

eosophagus, stomach, liver, gallbladder, pancreas, small intestine, large intestine, anus