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33. Internal organs. Basic structural plan of the internal organs
Divided into parenchymal and hallow [tubular] organs
•
1. Parenchymal organs [pancreas, liver, kidney, lungs, …]
• consist of parenchyma [specialized tissue carries out specific function of organs]
• Always have stromal capsule, which gives of connective tissue intercalations or trabecular into parenchyma
• Stroma contains nerves, blood and lymph vessel - provides support and performs trophic function
2. Hollow organs
• Have a lumen and are shaped like tubes of different diameters
• despite some fidderences in shape, walls of tubular organs are similar in structure
• formed by mucosa, submucosa and muscularis, on outside serosa or adventitia
Mucosa
• Internal layer of tubular organs of digestive, respiratory and urogenital system
• consists of surface epithelium and lamina propria of mucosa
Epithelium
• depending on function epithelia can be
1. stratified squamous – oral cavity, pharynx, oesophagus, portion of rectum
2. transitional – urinary tract
3. simple columnar or prismatic – stomach, intestine, trachea
4. stratified ciliary (nasal cavity, larynx)
• protects underlying tissue
• in some organs [intestine, kidney, stomach] it performs selective absorption of substances
• Mucus [secreted by goblet cells] keeps mucosa moist, protecting epithelium
• Basement membrane acts as elastic support tissue, containing blood vessels, lymph vessels, nerve fibers, lymphoid cells
Lamina propria
• situated to outside of basement membrane
• consist of loos fibrous CT, containing blood vessels, lymph vessels, nerve fibers, lymphoid cells
Lamina muscularis mucosae
• thin layer of smooth muscle cells
• during contraction forms folds
• in organs with simple epithelium or where main function is absorption [stomach, intestine] myocytes of muscularis
mucosae inter-wine with each other forming network structure
• in organs with secretion as main function - the smooth muscle cells have more disorderly orientation
Submucosa
• Contains some different simple branched glands, which secrete mucus and some bioactive substances
Muscularis externa
• Made up of smooth muscle cells which form two layers
• Internal layer is circular muscle, external layer is longitudinal muscle
• Function:
a. Provides muscle tone and performs rhythmic contractions [peristalsis] in organs of digestive tract
b. In respiratory pathways regulates width of the lamina bronchi
c. In urogenital tract it regulates lamina of the ducts of urinary and reproductive system
d. Sections of the digestive tract [mouth, pharynx, upper part of esophagus, external sphincter of rectum]
e. Muscle layer of muscularis forms thickening called sphincters which can narrow the lumen and close it
Adventitia
• formed by loose fibrous CT - contains blood and lymph vessel and nerves
• covers, protects and attaches internal organs to the walls of body cavities and to neighboring organs
Serosa
• Organs situated in abdominal cavity are covered on the outside bby serosa
• Lines abdominal part of oesophagus, stomach, mesenteric part of small intestine and parts of the large intestine
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• serosa layer of the lung is called pleura
• formed by a thin layer of dense CT - with elastic and collagen fibers
• contains blood and lymph vessels and nerve fibers
• contains large number of sensitive nerve ending
34. Digestive system – common study. Structure of its organs. Ontogenesis.
• Composed of two categories of organs:
1. Digestive organs - continuous tube 9 - 10 m long from mouth to anus
2. Accessory digestive organs - production/ secretion of enzymes and bile
Structures of the wall of digestive system:
• Alimentary system is basically a muscular tube lined with epithelium
• adapted regionally to various functions
Mouth and pharynx
• tongue is composed of striated lined by highly differentiated epithelial cells
• Teeth composed of various hard tissues
Organs of digestive tract
• Most of the organs have structurally similar walls - formed by several layers
Mucosa
• Epithelial lining - varies regionally and is characteristic for each segment
• Lamina propria - layer of CT containing capillaries, lymph vessels & glands with ducts opening on the epithelium
• Muscularis mucosae - thin muscular layer of smooth muscle
Submucosa
• Layer of underlying fibrous CT - separating mucosa from surrounding muscles, incl. fine bundles of nerve plexuses
Muscular layer
• two distinct layers of smooth muscle
1. Inner circular layer
2. Outer longitudinal layer
• Stomach - has a third layer [inner oblique] - responsible for churning
• Esophagus - part of the muscle layer is the skeletal muscle
Serosa or Adventitia
• Covers outer surface of intestinal canal with layers of CT continuous with the peritoneum which serves as a conduit for
blood vessels, lymph vessels and nerves serving the contained organs
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ONTOGENESIS
• Primitive gut is formed when a portion of the yolk sac becomes incorporated into the embryo - occurs due to the
cephalocaudal and lateral folding of the embryo
• has four sections
1. proximal foregut - extends from the oropharyngeal membrane to the respiratory diverticulum - [pharynx]
2. distal foregut - extends from pharyngeal tube to the liver bud
3. midgut - extends from liver bud -> junction between the right two-thirds and the left third of the transverse colon
4. hindugut - extends from the left third of the transverse colon to the cloacal membrane
In the abdominal cavity, the gut tube and its derivatives are suspended from the dorsal and ventral body wall by mesenteries; these
are double layers of peritoneum that enclose organs and connect them to the body wall
• Intraperitoneal organs - stomach
• Retroperitoneal organs - organs that lie directly on the posterior body wall and are covered by peritoneum on their
anterior surface [kidney]
• Peritoneal ligaments - Mesenteries between two organs or one organ and the body wall
•
Foregut
• gives rise to distal end of esophagus, the stomach and proximal end of duodenum
• a diverticulum from anterior aspect of foregut grows into ventral mesentery, giving rise to
liver and gallbladder and ventral part of the pancreas
• developing stomach rotates clockwise and associates with dorsal mesentery, moves to the
left and greatly expands
• mesentery associates with part of the stomach and fuses to the body wall
• The derivatives of the foregut, except for the pharynx and the lower respiratory system, are mostly supplied by the celiac
artery (trunk).
❖ Gives rise: pharynx, lower respiratory system, esophagus, stomach, proximal half of the duodenum, live, biliary appartus,
pancreas
Midgut
• develops into distal part of duodenum, the jejunum, the ileum, ascending colon and proximal 2/3 of transverse colon
• 2 limbs of the midgut loop rotate counterwise around their combined central axis and part of loop becomes cecum
• superior mesenteric artery (supplies midgut) is at center of the axis of rotation
• ascending colon fuses with body wall and transverse colon remains suspended by its dorsalmesentery (transverse
mesocolon)
• The derivatives of the midgut are supplied by the superior mesenteric artery.
❖ Gives rise: distal half of the duodenum, jejunum, ileum, cecum, appendix, ascending colon, proximal two-thirds of the
transverse colon
fifth week of gestation, the midgut undergoes a rapid elongation that occurs much faster than that of the abdominal cavity, resulting
in the formation of the primary intestinal loop.
At its apex, the loop remains in open communication with the yolk sac via the vitelline duct, while the superior mesenteric
artery runs along the axis of the loop.
sixth week: the continuing elongation of the midgut, combined with the pressure exerted by the dramatic growth of the abdominal
organs, force the primary intestinal loop to protrude into the umbilicus (physiological herniation)
Concurrently, the loop rotates 90 degrees counterclockwise around the axis of superior mesenteric artery - until the eighth
week
‣ cranial limb moves caudally and to the embryo’s right
‣ caudal limb to move cranially and to the embryo’s left
After the eighth week:
‣ lengthening jejunum and ileum develop into a series of folds known as the jejunal-ileal loops
‣ the expanding cecum gives rise to a wormlike diverticulum - the vermiform appendix.
Tenth week - the herniated midgut retracts into the abdomen -> cecum -> ascending colon
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Eleventh week - intestines have formed
Hindgut
• develops into distal 1/3 of transverse colon, descending colon, sigmoid colon and superior part of rectum
• proximal parts of hindgut swing to left and become decending colon and sigmoid colon
• descending colon and its mesentery fuse to the body wall
• sigmoid colon passes through pelvic inlet and is continuous with rectum
• The derivatives of the hindgut are supplied by the inferior mesenteric artery.
❖ Gives rise:transverse colon, descending colon, sigmoid colon, rectum, upper two-thirds of the anal canal
35.Oral cavity – parts. Ontogenesis and anomalies of the face and oral cavity
The oral cavity is an internal area of the head - is created by the bony space between the base of the skull and its connection to the
mandible via the temporomandibular joint
• It extends from the lips and cheeks externally to the anterior pillars of the fauces internally and continues into the
oropharynx
• contains the Lips (labia), the gums (gingivae) and the Labial frenulum
Divided into three segments:
1. Vestibulum oris - space between the cheeks/ lips and the teeth
2. Cavum oris proprium - ventral and lateral bordered by alveolar processes and the teeth sticking into them/ superior
and caudal bordered by the bottom of the mouth
3. Isthmus faucium - forms the junction of the oral cavity with the pharynx
Function:
• Is the entrance to the alimentary canal, the area in which the first stages of digestion occur through mastication, and due to
the movements of the inner and adjacent structures such as the tongue, the lips and the teeth
• initiate the digestive process by salivation and propulsion of the alimentary bolus into the pharyn
• speech
• Respiratory function
Border:
• Anterior: teeth limit the oral cavity proper
• superior: the hard palate, soft palate - form the roof of the cavity
• Inferior: tongue and the floor of the mouth
• Posterior: larynx, pharynx, tonsils - marking the end of the cavity proper and the tip of the soft palate
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