5. GROSS ANATOMY, ABD. CAVITY
• The abdominal cavity forms the superior and major
part of the abdomino-pelvic cavity
• The cavity, extends between the thoracic diaphragm
and the pelvic diaphragm.
• The plane of the pelvic inlet (superior pelvic
aperture) arbitrarily, but not physically, separates the
abdominal and the pelvic cavities. The cavity extends
superiorly into the osseocartilaginous thoracic cage
to the 4th intercostal space
6. ABDOMINAL CAVITY
In summary, the abdominal cavity is
• The major part of the abdominopelvic cavity.
• Located between the diaphragm and the pelvic
inlet.
• Separated from the thoracic cavity by the
thoracic diaphragm.
• Continuous inferiorly with the pelvic cavity.
• Supported and partially protected inferiorly by the
greater pelvis.
• Enclosed anterolaterally by multi-layered,
musculoaponeurotic, abdominal walls.
7. ABDOMEN: SURFACE MARKINGS
Divided into 9 regions by two vertical lines and two
horizontal lines:
The mid-clavicular lines
The Sub-costal line and Transtubercular line/plane
8.
9.
10. EMBRYOLOGY
Human development begins at fertilization
when a male gamete or sperm unites with a
female gamete or oocyte to form a single
cell, a zygote.
The sperm and oocyte, are highly
specialized sex cells. Each of these cells
contains half the number of chromosomes
(haploid number)
SPERMATOGENESIS: is the sequence of
events by which spermatogonia are
transformed into mature sperms. This
maturation process begins at puberty.
11. OOGENESIS
Oogenesis (ovogenesis) is the sequence of
events by which oogonia are transformed into
mature oocytes. This maturation process
begins before birth and is completed after
puberty. Oogenesis continues to menopause,
which is permanent cessation of the menses
(bleeding associated with the menstrual
cycles).
12. FERTILIZATION
The usual site of fertilization is the ampulla of the
uterine tube, its longest and widest part. If the
oocyte is not fertilized here, it slowly passes along
the tube to the uterus, where it degenerates and is
resorbed.
Chemical signals (attractants), secreted by the oocyte
and surrounding follicular cells, guide the
capacitated sperms (sperm chemotaxis) to the oocyte
13. SUMMARY OF THE FIRST WEEK
Oocytes are produced by the ovaries (oogenesis) and
expelled from them during ovulation. The fimbriae of the
uterine tube sweep the oocyte into the ampulla where it
may be fertilized.
Sperms are produced in the testes (spermatogenesis)
and are stored in the epididymis. Ejaculation of semen
during sexual intercourse results in the deposit of
millions of sperms in the vagina.
When an oocyte is contacted by a sperm, it completes
the second meiotic division. As a result, a mature
oocyte and a second polar body are formed. The
nucleus of the mature oocyte constitutes the female
pronucleus.
14. WEEK 1:
After the sperm enters the oocyte, the head of the
sperm separates from the tail and enlarges to become
the male pronucleus. Fertilization is complete when the
male and female pronuclei unite and the maternal and
paternal chromosomes intermingle during metaphase
of the first mitotic division of the zygote.
As it passes along the uterine tube toward the uterus,
the zygote undergoes cleavage (a series of mitotic cell
divisions) into a number of smaller cells-blastomeres.
A cavity forms in the morula, converting it into a
blastocyst consisting of the embryoblast, a blastocystic
cavity, and the trophoblast.
15. WEEK 1:
Four to 5 days after fertilization, the zona pellucida
is shed and the trophoblast adjacent to the
embryoblast attaches to the endometrial epithelium.
The trophoblast at the embryonic pole differentiates
into two layers, an outer syncytiotrophoblast and an
inner cytotrophoblast. The syncytiotrophoblast
invades the endometrial epithelium and underlying
connective tissue. By the end of the first week, the
blastocyst is superficially implanted in the
endometrium.
16. ORGANOGENESIS
Fourth to Eighth Weeks:
All major external and internal structures are established
during the fourth to eighth weeks.
As the tissues and organs form, the shape of the embryo
changes, and by the eighth week, it has a distinctly
human appearance. Because the tissues and organs are
differentiating rapidly during the fourth to eighth
weeks, exposure of embryos to teratogens during this
period may cause major congenital anomalies.
17. GIT: EMBRYOLOGY
The primordial gut at the beginning of the fourth
week is closed at its cranial end by the
oropharyngeal membrane and at its caudal end by
the cloacal membrane.
The primordial gut forms during the fourth week as
the head, tail, and lateral folds incorporate the dorsal
part of the umbilical vesicle into the embryo
The endoderm of the primordial gut gives rise to
most of its epithelium and glands. The epithelium at
the cranial and caudal ends of the alimentary tract is
derived from ectoderm of the stomodeum and
proctodeum
18. GIT
The derivatives of the foregut are:
The primordial pharynx and its derivatives
The lower respiratory system
The esophagus and stomach
The duodenum, proximal to the opening of the bile
duct
The liver, biliary apparatus (hepatic ducts,
gallbladder, and bile duct), and pancreas
19.
20. EMBRYOLOGY OF GIT
Development of the Stomach The distal part of the
foregut is initially a simple tubular structure. Around
the middle of the fourth week, a slight dilation
indicates the site of the primordium of the stomach.
It first appears as a fusiform enlargement of the
caudal or distal part of the foregut and is initially
oriented in the median plane.
The primordial stomach soon enlarges and broadens
ventrodorsally. During the next 2 weeks, the dorsal
border of the stomach grows faster than its ventral
border; this demarcates the greater curvature of the
stomach
21. MID GUT
The midgut gives rise to the duodenum (the part
distal to the entrance of the bile duct), jejunum,
ileum, cecum, appendix, ascending colon, and the
right one half to two thirds of the transverse colon.
The midgut forms a U-shaped umbilical loop of the
intestine that herniates into the umbilical cord during
the sixth week because there is no room for it in the
abdomen. While in the umbilical cord, the midgut
loop rotates counterclockwise 90 degrees. During the
10th week, the intestines return to the abdomen,
rotating a further 180 degrees during this process.
22. HIND GUT
The hindgut gives rise to the left one third to one half
of the transverse colon, the descending and sigmoid
colon, the rectum, and the superior part of the anal
canal. The inferior part of the anal canal develops
from the proctodeum.
The rectum and superior part of the anal canal are
separated from the exterior by the anal membrane.
This membrane normally breaks down by the end of
the eighth week.
23. ESOPHAGUS: GROSS ANAT
The esophagus is a muscular tube (approximately 25
cm [10 in.] long) with an average diameter of 2 cm
that conveys food from the pharynx to the stomach
It originates at the distal end of the laryngopharynx
(hypopharynx), at the level of the sixth cervical
vertebra.
3 Constrictions:
1. Cervical constriction: at its beginning at the
pharyngoesophageal junction, caused by the
cricopharyngeus muscle
2. Thoracic (broncho-aortic) constriction caused by
arch of the aorta and left main bronchus
3. Diaphragmatic constriction
24. ESOPHAGUS
Has internal circular and external longitudinal
layers of muscle. In its superior third, the
external layer consists of voluntary striated
muscle; the inferior third is composed of smooth
muscle, and the middle has both.
Passes through the elliptical esophageal hiatus in
the muscular right crus of the diaphragm, just to
the left of the median plane at the level of the
T10 vertebra.
Terminates by entering the stomach at the cardial
orifice.
30. STUDY QUESTIONS
1. Describe the relations of the inguinal canal
2. Discuss the blood supply of the intestines,
correlate this with the embryological development
of the gut
3. With the aid of a well labeled diagram
demonstrate the sub-divisions of the peritoneal
cavity
