3 Hyman Digestive System

Comparative Anatomy of the Vertebrates:

[BIOLOGY 102 LAB:

Coelom, Digestive and Respiratory Systems]

OUTLINE I. Oral cavity and pharynx A. Salivary glands B. Oral Cavity C. Pharynx II. Hyoid apparatus, larynx, trachea, and esophagus A. Hyoid apparatus B. Larynx C. Trachea D. Esophagus III. Pleural and pericardial cavities A. Lungs B. Heart C. Diaphragm IV. Peritoneal cavity A. Liver B. Gallbladder C. Stomach D. Spleen E. Small Intestine F. Peyer’s Patches G. Pancreas H. Caecum I. Large Intestine / Colon J. Rectum K. Anus L. Cavities, Ligaments And Mesenteries M. Ducts

I.

ORAL CAVITY AND PHARYNX A. SALIVARY GLANDS – outgrowths of the oral epithelium SALIVARY DUCTS – stalk of each outgrowth 1. PAROTID GLAND  ventrad and craniad of the base of the pinna PAROTID DUCT  

passes across the external surface of the masseter muscle penetrates the upper lip

2. SUBMAXILLARY GLAND  roundish mass  angle of the jaw near the posterior margin of the masseter SUBMAXILLARY DUCT    

accompanied by the SUBLINGUAL DUCT in cats pass internal to the digastric and mylohyoid muscle situated external to the lining of the mouth cavity runs forward nearly to the symphysis of the mandible and then penetrates the lining

3. SUBLINGUAL GLAND  elongated  surrounds the submaxillary duct 4. MOLAR GLAND  present in cats only  situated between the skin and the external surface of the mandible, in front of the masseter 5. INFRAORBITAL GLAND  lies in the floor of the orbit B. ORAL CAVITY 1. LIPS and CHEEKS  boundary of the oral cavity 2. VESTIBULE  lies between the teeth and lips 3. HARD PALATE  anterior portion of the roof of the oral cavity  supported by the premaxillary, maxillary and palatine bones  mucous thrown into roughened transverse ridges 4. SOFT PALATE  posterior portion of the roof of the oral cavity  lacks bony support

Comparative Anatomy of the Vertebrates:

[BIOLOGY 102 LAB:

Coelom, Digestive and Respiratory Systems]

5. NASOPALATINE DUCTS  pair of openings found at the anterior end of the hard palate, behind the incisor teeth  connect the mouth and nasal cavities by way of the INCISIVE FORAMINA of the maxillary bones 6. TONGUE  fleshy muscular organ  formed by the fusion of four components: (a) primary tongue (b) gland field/ tuberculum impar (c) a pair of lateral lingual swellings 7. FRENULUM  vertical fold  anterior margin of the attachment of the tongue to the floor of the oral cavity  in cats, a fold runs forward from the frenulum on each side within the teeth, and terminates anteriorly in a wellmarked flattened papilla which bears the openings of the submaxillary and sublingual ducts 8. FILIFORM PAPILLAE  covers the anterior part of the tongue  hard and spine-like  pointed posteriorly  provided with microscopic taste buds 9. FUNGIFORM PAPILLAE  covers the remainder of the tongue  provided with microscopic taste buds 10. VALLATE PAPILLAE  four to six  arranged in V-shaped row  each consisting of a round elevation set into a pit  at its sides are some very large fungiform papillae

C. PHARYNX – lies posterior and dorsal to the soft palate 1. EPIGLOTTIS  leaf-shaped structure that conceals the pharynx’s free posterior margin  projects from the base of the tongue  guards the entrance into the respiratory tract 2. ISTHMUS OF FAUCES  opening formed by the free border of the palate  leads into the cavity of the pharynx 3. TONSILLAR FOSSA  pits shortly anterior to the free border of the soft palate on each side  contains the palatine tonsil  bounded in front and behind by low folds: (a) anterior GLOSSOPALATINE ARCH (b) posterior PHARYNGOPALATINE ARCH 4. PALATINE TONSIL  small mass of lymphoid tissue 5. NASOPHARYNX  revealed dorsal to the soft palate upon slitting along its median line 6. POSTERIOR NARES / CHOANAE  anterior end of the nasopharynx  internal ends of the nasal passages 7. AUDITORY/EUSTACHIAN TUBE  pair of oblique slits posterior to the choanae on the lateral wall of the nasopharynx  canals which connect the pharynx with the cavity of the middle ear “Because of the formation of the palate and the consequent posterior migration of the posterior nares, the air no longer enters the oral cavity, but proceeds directly into the pharynx”

Comparative Anatomy of the Vertebrates:

II.

[BIOLOGY 102 LAB:

Coelom, Digestive and Respiratory Systems]

HYOID APPARATUS, LARYNX, TRACHEA, AND ESOPHAGUS

5. TRUE VOCAL CORDS  extends from the arytenoids cartilages to the thyroid cartilages  nearly occlude the opening

A. HYOID APPARATUS – mammals: derived from the second and third gill arches – supports the base of the tongue – serves for the origin and insertion of muscles

6. FALSE VOCAL CORDS  cats: situated lateral to the true vocal cords and extending from the tips of the arytenoids to the base of the epiglottis

1. HYOID BODY  rabbit: stout bone  cat: narrow bar

C. TRACHEA / WINDPIPE – posterior to the larynx – its walls are stiffened by cartilaginous rings, which are dorsally incomplete, leaving a soft strip in the dorsal wall of the trachea into which the esophagus fits

2. HORNS / CORNUA  rabbit: short processes which are connected by slender, tendinous muscles with the jugular process of the occipital bone  cat: long and slender ANTERIOR horn, consist of a chain of four bony pieces, the last which articulates with the tympanic bulla; short POSTERIOR horn united to the larynx

1. THYROID GLAND  flattened elongated body lying against the trachea and internal to the muscles  anterior end of each lobe is at a level with the cricoid cartilage 2. ISTHMUS  connects the caudal ends of the two lobes  crosses the ventral side of the trachea

B. LARYNX / VOICE BOX – chamber with cartilaginous wall – constitutes the projection in the throat, ADAM’S APPLE 1. GLOTTIS  a large opening is situated on the top of the larynx  epiglottis projects from its ventral margin 2. THYROID CARTILAGE  a large shield-shaped cartilage  supports the ventral wall of the larynx 3. CRICOID CARTILAGE  posterior to the thyroid cartilage  forms a ring around the larynx 4. ARYTENOIDS  pair of projecting cartilages  supports the dorsal rim of the glottis between the glottis and the opening of the esophagus

D. ESOPHAGUS – soft tube which proceeds posteriorly dorsal to the larynx III.

PLEURAL AND PERICARDIAL CAVITIES MAMMALIAN TRUNK Divisions:  anterior THORACIC region 3 coelomic cavities:  2 laterally located PLEURAL cavities  1 median PERICARDIAL cavity  posterior ABDOMINAL region A. LUNGS - composed of innumerable minute aircells, ALVEOLI  right lung > left lung  divided into 3 lobes:  smaller ANTERIOR  larger MIDDLE  POSTERIOR

Comparative Anatomy of the Vertebrates:

[BIOLOGY 102 LAB:

Coelom, Digestive and Respiratory Systems]

 MEDIAL lobe - projects into a pocket formed by a special, dorsally directed fold of the mediastinal septum, CAVAL FOLD  LATERAL lobe 1. PLEURAL CAVITY/SAC  contains the soft spongy lung 2. MEDIASTINAL SEPTUM  partition which stretches from the heart to the ventral median line  consist of the two medial walls of the right and left pleural sacs in contact with each other 3. MEDIASTINUM  space between the two walls of the mediastinal septum (that separate at the level of the heart)

4. PLEURA  smooth moist membrane lining the pleural sac Division: (a) PARIETAL pleura  lines the inside of the pleural cavity  covers the anterior face of the diaphragm  forms the MEDIASTINAL SEPTUM together with the MEDIAL WALL of the other pleural sac (b) VISCERAL pleura  passes over the surface of the lung to which it is indistinguishably fused 5. CAVAL FOLD  supports the POSTCAVAL VEIN which ascends from the liver to the heart and inclosed in the free dorsal margin of the fold

B. HEART – surrounded by 3 coelomic layers: visceral pericardium, parietal pericardium, and parietal pleura of the mediastinal septum 1. PARIETAL PERICARDIUM  pericardial sac  sac of thin tissue inclosing the heart, attached at its anterior end, where vessels enter and leave the heart  separated from the heart by the pericardial cavity 2. VICERAL PERICARDIUM  invested at the surface of the heart  inseparably adherent to the heart wall  continuous with the pericardial sac at the anterior end 3. PERICARDIAL CAVITY  narrow space between the pericardial sac and the heart 4. THYMUS  mass of gland issue extending forward in the median line ventral to the anterior part of the heart  larger in younger specimen  gland of the internal secretion  derived from the entodermal lining of gill pouches of the embryo  development of cells of the immune system, T-cells 5. RADIX / ROOT  narrow region that serves as the attachment of the lung  artery, vein, bronchus pass to the lung and veins from the lung 6. PULMONARY LIGAMENT  cat: a pleural fold to which the lung is attached (to the dorsal thoracic wall) 7. DORSAL AORTA  large vessel injected which arches away from the heart to the left and descend toward the diaphragm

Comparative Anatomy of the Vertebrates:

[BIOLOGY 102 LAB:

Coelom, Digestive and Respiratory Systems]

C. DIAPHRAGM  muscular dome-shaped partition  forms the posterior wall of the pleural sac  separates the pleural from the peritoneal cavity  consist partly of the transverse septum and other coelomic membranes; then invaded by muscle buds from the adjacent cervical myotomes  plays an important role in respiratory movements  ORIGIN: ribs, sternum, vertebrae  INSERTION: central tendon  its center consist of connective tissue forming a circular tendon, CENTRAL TENDON  peculiar to mammals  penetrated by the ESOPHAGUS, AORTA, and POSTCAVAL VEIN “When contracted, the diaphragm flattens, thus lengthening the pleural cavities posteriorly and causing air to rush into the lungs.”

IV.

PERITONEAL CAVITY – abdominal cavity  its anterior wall is formed by the DIAPHRAGM  lined by a membrane, PERITONEUM Division:  PARIETAL peritoneum  VISCERAL peritoneum / SEROSA A. LIVER – grayish brown in preserved specimens  convex anterior and concave posterior surfaces  divided into RIGHT and LEFT lobes, each of which is subdivided into MEDIAN and LATERAL  left lateral > right lateral  right medial > left medial  cat: RIGHT LATERAL lobe is deeply cleft into two lobules  situated between the stomach and the liver is a small CAUDATE lobe  secretes bile, stores and filters blood, and takes part in metabolic functions, for example, the conversion of sugars into glycogen.

B. GALLBLADDER – imbedded in the right median lobe  rabbit: on its dorsal surface  cat: cleft  storage and concentration of bile C. STOMACH 1. CARDIA  area of junction of the stomach and esophagus 2. CARDIAC END  region adjacent to the cardia 3. FUNDUS  saclike bulge to the left of the cardia 4. BODY 5. PYLORUS  area of junction of the stomach and small intestine 6. PYLORIC VALVE  thickened ridge inside the pylorus 7. PYLORIC END  constriction, beyond which the small intestine makes an abrupt bend 8. GREATER CURVATURE  larger, convex posterior surface of the stomach from the cardia to the pylorus 9. LESSER CURVATURE  shorter slightly concave anterior surface 10. RUGAE  marked ridges in the wall of the stomach D. SPLEEN – attached to the left border of the stomach  helps to destroy old red blood cells, form lymphocytes, and store blood E. SMALL INTESTINE  digestion and absorption

Comparative Anatomy of the Vertebrates:

[BIOLOGY 102 LAB:

Coelom, Digestive and Respiratory Systems]

1. DUODENUM  supported by a part if the dorsal mesentery, the MESENTERY PROPER 2. JEJUNUM 3. ILEUM 4. VILLI  fingerlike projections of the mucous membrane 5. ILEOCOLIC VALVE  elevation projecting into the ileum F. PEYER’S PATCHES – aggregations of lymph nodules present in the wall of the intestine  thickened oval light-colored spots along the colon G. PANCREAS – definite, compact, pinkish gland  secretes juices into the small intestine  secretes hormones, glucagon, insulin and somatostatin into the blood stream H. CAECUM – marks the junction of small and large intestine  vermiform appendix absent I.

LARGE INTESTINE / COLON  passes forward as the ASCENDING COLON; then urns and extends across the peritoneal cavity from right to left as the TRANSVERSE COLON; then turns abruptly at the left and proceeds straight posteriorly as the DESCENDING COLON  extract water and form feces

J. RECTUM  terminal portion of the descending colon K. ANUS  opening at the lower end of the alimentary canal through which feces are released L. CAVITIES, LIGAMENTS AND MESENTERIES 1. MESENTERIES / LIGAMENTS – double-walled membranes formed by the peritoneum

(a) DORSAL mesentery  specifically, the MESENTERY PROPER, supports the duodenum  intact in mammals (b) VENTRAL mesentery  persist in the region of the liver and urinary bladder 2. MESOGASTER  passes over the stomach  forms the visceral peritoneum of the stomach  incloses the stomach between its walls 3. GREATER OMENTUM  owes its origin in part to the rotation of the stomach  its line of attachment to the greater curvature is original dorsal surface of the stomach, while the lesser curvature is the original ventral surface 4. GASTROHEPATODUODENAL LIGAMENT/ LESSER OMENTUM  passes from the lesser curvature of the stomach to the posterior surface of the liver Division: (a) GASTROHEPATIC LIGAMENT  from the lesser curvature to the liver  its portion which contains the caudate lobe forms a LESSER PERITONEAL SAC which continues anteriorly the cavity of the greater omentum (b) HEPATODUODENAL LIGAMENT  from the liver to the duodenum  in which the common bile duct passes to the intestine  HEPATIC PORTAL VEIN  has a free border which forms the ventral rim of an opening or slit, FORAMEN EPIPLOICUM, which serves as the entrance into the cavity of the omentum

Comparative Anatomy of the Vertebrates:

[BIOLOGY 102 LAB:

Coelom, Digestive and Respiratory Systems]

5. GASTROSPLENIC / GASTROLIENAL LIGAMENT  portion of the great omentum between the spleen and the stomach 6. GASTROCOLIC LIGAMENT  secondary fusion formed between the mesogaster ant the mesentery of the intestine 7. FALCIFORM LIGAMENT  extends from between the two median lobes of the liver to the median ventral line  thin sheet with concave posterior border 8. CORONARY LIGAMENT  stout ligament  attaches to the liver to the central tendon of the diaphragm  circular in form and its ring of attachment to the liver bounds a small space on the anterior face of the liver which is free from serosa 9. MESODUODENUM  part of the dorsal mesentery  supports the duodenum 10. DUODENORENAL LIGAMENT  attaches the duodenum to the right kidney M. DUCTS 1. COMMON BILE DUCT  bounds the duodenum to the liver  cystic duct + hepatic duct 2. BILE DUCT  runs in the hepatoduodenal ligament 3. CYSTIC DUCT  from the gall bladder 4. HEPATIC DUCT  from the lobes of the liver

5. PANCREATIC DUCT (a) principal duct – joins the common bile duct at the point where the latter enters the duodenum (b) secondary/accessory duct – enters the duodenum 6. AMPULLA OF VATER  slightly swollen chamber where bile and pancreatic ducts unite