Lab 1: Digestive System and Body Cavities (Rat Dissection)

Question 1

How is orientation conducted?

Answer 1

via Relative positioning

Question 2

How do you orientate a rat?

Answer 2

Anterior = forward (in front)
Posterior = behind
Dorsal = top (like a fin)
Ventral= beneath (belly-side)

Looking at the rat head facing us
Medial = towards Midline
Lateral= away from midline

Question 3

How do you orientate humans?

Answer 3

Humans are UPRIGHT
Anterior= ventral
Posterior= dorsal
Superior= towards the head (cranial)
Inferior= towards the tail/feet (caudal)
Meidal and lateral also applicable to humans (ears to our nose)

Question 4

What is a rat?

Answer 4

Rattus Norvegicus Albinus
example of a generalised mammal, showing digestive systems and body cavities
Fully grown (300grams) at 6-8 months
Lifespan 3 years

Question 5

What are the features of a rat?

Answer 5

1. 2x front incisors which are developed and sharp. Chisel shaped. Adapted for Gnawing. Gap between incisors= variable, and can be changed at will. No canines.
   Anterior of teeth= covered with enamel. Posterior= no enamel.
   Lower jaw (mandible) in 2x pieces , hinged in the middle.
2. have Whiskers called= Vibrissae, which are TACTILE organs for sense/fell without sight in darkness
3. Nostrils called=nares and can open/close, which prevents water from entering when rats are in water
4. Tail is a BALANCING organ for balance
5. Pentadactyl like human, have 5 digits on their paws

Question 6

What are the rats body cavities?

Answer 6

3x different major body cavities

1. Peritoneal cavity (gut)
2. Pericardial cavity (heart)
3. Two Pleural cavities (1 per lung)

Question 7

What are the features of the gut wall?

Answer 7

1. Layer of Parietal Peritoneum Lines the body wall, including Abdominal Wall of the Gut
2. Visceral Peritoneum is the layer in contact with the organs
3. B/w 2x layers is the Peritoneal Cavity/Space, where there is ONLY SEROUS FLUID (no organs)
4. serous fluid is a Thin film which acts as a Lubricant to let the gut wall move around w/o causing Friction against the abdominal wall. Wet slippery surface. rubbing together of Organs = INFLAMMATION.
5. Serous Membrane = Thin layer of MESOthelial cells, which SECRETE serous fluid.
6. (other cavities are lined in a similar way, & serous fluid serves the same purpose (pericardial cavity, prevents friction of heart and Thoracic cavity when the heart Beats))
7. in the peritoneum, MESENTERY SUSPENDS the organs, holing them IN PLACE at the Dorsal body wall. Mesentery is a Double layer of Peritoneum, and the visceral peritoneum and parietal peritoneum are CONTINUOUS with one another. FANS out. is a TRANSLUCENT and SLIPPERY layer.

Question 8

What does the Thoracic cavity contain?

Answer 8

OTTHL
oesophagus
trachea
thymus
heart
lungs

Question 9

What does the Abdominal cavity contain?

Answer 9

SSSPLLiC
stomach
small intestine
spleen
pancreas
large intestine
liver
caecum

Question 10

What is the diaphragm?

Answer 10

the physical barrier between the Abdominal and Thoracic cavity

Question 11

What does the human Dorsal Body Cavity and Ventral Body Cavity consist of?

Answer 11

Dorsal=  Cranial(brain) + Vertebral(spinal cord)
Ventral= Thoracic(heart&lungs) + Diaphragm + Abdominal(digestive viscera) + Pelvic (bladder&repro.organs&rectum)

Question 12

What are the lungs of a rat like?

Answer 12

Rats killed with CO2 gas, due to Haemorrhage from Small Blood Vessels in the lungs
Both lungs are likely to be Dark Red(Blood Filled)
Normally healthy Pink colour and Spongy

Question 13

What is the heart of a rat like?

Answer 13

Dissect rat lying on its back
Head = Anterior (In front of the heart)
Being heart = Posterior
Anterior end of the heart ‘base’ can see the THYMUS Gland. part of the Lymphatic system, role in formation of T-lymphocytes.

Question 14

What is the blood supply to the Gut like?

Answer 14

Aorta carries blood away From the heart
Various Branches of blood vessels from the Aorta, which supply Organs of the body
a. Coeliac Artery = supplies Foregut
b. Superior Mesenteric Artery = supplies Mid gut
c. Inferior Mesenteric Artery= supplies Hind gut

Question 15

What is the sequential order of the Digestive system?

Answer 15

MOSSIL

Mouth–> Oesophagus –> Stomach –> Small Intestine –> Large intestine

Question 16

What is the sequential order of the Small Intestine in the Digestive system?

Answer 16

Small Intestine is Segmented in order into the DJI
Duodenum –> Jejunum –> ileum
Duodenum is the closest to the stomach

Question 17

What is the sequential order of the Large Intestine in the Digestive system?

Answer 17

Large intestine is Segmented in order into the CC(ATD)RA

Caecum –> Colon (1. Ascending 2. Transverse 3. Descending) –> Rectum –> Anus

Question 18

Whites the gut tube of a rat like?

Answer 18

1. Convoluted in order to be long (5x Body Length)
2. Increases SA for the ABSORPTION and SECRETION everywhere Downstream Oesophagus
3. gut contains:
   a. 3x Tubular portions = Oesophagus, Small intestine, Large Intestine
   b. 2x sacs = Stomach & Caecum
4. SECRETION occurs in the 2x Large GLANDS (Liver & Pancreas). are Developed Embryologically From the Gut LINING and are ACCESSORY Organs along with the Teeth, Tongue and Salivary Glands

Question 19

What is the gut categorised into?

Answer 19

3x Tubular = Oesophagus, Small Intestine, Large Intestine
2x Sacs = stomach , caecum
2x Large Gands = Liver, Pancreas (secretion) (embryologically from gut lining)
5x Accessory Organs = secretion = Liver, Pancreas, Teeth, Tongue, Salivary Glands (LPTTS)

Question 20

What is the role of the Oesophagus?

Answer 20

1. responsible for Rapid Transport of the food Bolus from the Mouth –> Stomach
2. Some Voluntary control = Skeletal Muscle = Swallowing
   but Peristalsis = Smooth muscle = Involuntary control
3. Oesophagus travels from the Throat –> Thoracic Cavity
4. Oesophagus is Dorsal to the Heart and Lungs to the Diaphragm

Question 21

What is the positioning of the Oesophagus?

Answer 21

Oesophagus is Dorsal to the Heart and Lungs to the Diaphragm
What is the positioning of the Stomach?
Rat Stomach is: 
Posterior(behind) to the Oesophagus
Anterior(forward) to the Gut Tract

Question 22

What is the role of the stomach?

Answer 22

1. stomach is Posterior to the Oesophagus and Anterior to the Gut Tract
2. Curved organ - has 1x side which is More Medial to the other (other side is on the Left side)(lies mostly on the Left side)
3. stomach’s Smaller curved side = Lesser Curvature= formerly Ventral surface
   stomachs Larger curved side = more Lateral = Greater Curvature = formerly Dorsal surface

Question 23

What is the Rat Stomach Comprised of?

Answer 23

1. Anterior Lateral Region =
   Thin + Translucent, used for Food Storage, Stratified Squamous cells, No glands
2. Posterior Medial Region (Pyloric region)=
   Glandular + Opaque, contains glands which secrete Enzymes, Acid and Mucous to Aid digestion. this is because the PYLORIC SPHINCTER connects the S.I. to –> the Stomach. this is Smooth muscle the Opens/Closes to Control the passage of CHYME(digested food) through to –> the First portion for the gut tract (Duodenum). This is Involuntary Muscle.

Question 24

What connects the stomach to the S.I.?

Answer 24

Pyloric Sphincter
connects the small intestine and stomach
is smooth muscle (involuntary)
opens and closes to Control passage of Chyme (digested for) through to –> the Duodenum (1st portion of gut tract)

Question 25

What is the role of the Small Intestine?

Answer 25

1. main function of the S.I. = Absorption of Small molecules resulting from Digestion 2. Tube of Uniform diameter 3. about 4x body lengths from Inlet--> to Outlet 4. 3x regions (DJI) Duodenum --> Jejunum --> ileum 5. lifting up the coils, they are attach to the DORSAL body walls by a transparent MESENTERY which is a Double layer (2x) of VISCERAL Peritoneum 6. Opening of the Duodenum receives A. Chyme from Stomach B. Bile from Liver C. Pancreatic Juices from Pancreas 7. Blood supply of the S.I. involves blood vessels which Fan out through the Mesentery to Supply and Drain the Intestinal Wall. 7. a. Arteries= Carry HP + O blood TO the Intestinal wall and are 2x branches of the Dorsal Aorta (Coeliac artery and Superior Mesenteric artery). 7. b. Veins= DRAIN DEO, Nutrient Rich blood From the wall and are Tributaries of the HEPATIC Portal VEIN which lead to the LIVER

Question 26

What does the Blood Supply of the Small intestine comprise?

Answer 26

Blood vessels which Fan out through the Mesentery, and supply and drain the Intestinal wall a. Arteries = Carry HP + O blood TO the intestinal wall, and are the 2x branches of the Dorsal Aorta (Coeliac Artery and superior Mesenteric Artery) b. Veins = Drain DEO + Nutrient Rich blood From the wall, and are TRIButaries of the HEPATIC Portal VEIN which lead to the LIVER

Question 27

What is the role of the large intestine?

Answer 27

separated into 4x sections Caecum --> Colon --> Rectum --> Anus Main function is to REABsorb water from Digested foods. as more water is Reabsorbed, harder faeces result from the Undigested Food Residue. Bacteria contributes to the Putrification (deterioration or decay) of this material

Question 28

What is the role of the caecum?

Answer 28

Caecum Immediately follows the Small Intestine Rat caecum contains BACTERIA that produces CELLULASE enzymes which Digest Cellulose Humans have an APPENDIX called a VERMIFORM organ, which Terminates at the CAECUM and is a LYMPHOID organ (part of the lymphatic system) Rats DONT have a true Vermiform Appendix (don't have an appendix at all) or GallBladders

Question 29

What is the role of the Colon?

Answer 29

Colon is part of the Large Intestine which STORES faeces. Split into 3x sections, similar to human colon (ATD)(Ascending, Transverse, Descending) Rat colon ISNT as perfectly orientated as its human counterpart Faeces will move through the colon in a certain direction 1. Ascending - moves up the RIGHT side of the rat body in an ANTERIOR direction. Here the faeces are Upstream and are SEMI-firm 2. Transverse - travels ACROSS the body 3. Descending - moves down the LEFT side of the rate body in a POSTERIOR direction. the faeces are DOWNSTREAM and are more SOLID as WATEr has been REABSORBED.

Question 30

What is the function of the Rectum and Anus?

Answer 30

Rectum and Anus are Sites of Excretion 1. Rectum= Short passage leading up to the Anal outlet. Stores faeces prior to excretion. 2. Anus is under Partial Voluntary control. the anus has 2x Sphincters. Sphincters are segments of Muscle that can Open/close which allows Faeces to be VOIDED(discharged) a. Internal INvoluntary sphincter is made of Smooth muscle and will Relax when you Secrete Faeces b. External voluntary Sphincter is made of Skeletal Muscle

Question 31

What is the role of the Liver?

Answer 31

Hepatic = Liver Liver is the Largest Gland of the body. Function concerned with Metabolic Regulation and bile Production composed of 4x Lobes Dark red due to DUAL Vascular blood supply 1. Hepatic Artery (connected to coeliac artery) 2. Hepatic Portal Vein Hepatic portal vein is a Portal system which carries DEO blood from the GUT--> LIVER Portal system/vein transfers blood between Capillary beds(lots of capillaries) WITHOUT going to the Heart First Functionally the Liver is BOTH an Endocrine and Exocrine gland, like the pancreas. 1. Exocrine: Secretes BILE. which is made of EXCRETORY PROducts, involved in DIGESTIVE process as Bile Salts aid digestion and ABSORPTION by EMULSIFICATION of Fats and Vitamins. Humans have a Gallbladder to STORE BILE before discharging into the duodenum, whereas rats DONT have a gallbladder. 2. Endocrine: Secretes HORMONES

Question 32

What is the role of the Pancreas?

Answer 32

Pancreas sits just UNDER the Great curvature of the Stomach (near the spleen) feather shaped (looks like Scattered Pink Lobules) supported by the Mesentery (held in place) found more Medial, towards the Duodenum. Rat pancreas is MORE DIFFUSE than human pancreas Like the liver, pancreas is also Dual purpose as an Endocrine and Exocrine organ 1. Exocrine: secretes Alkaline Pancreatic Juices, which provide Enzymes for Digestion, such as AMYLASES, PROTEINASES and LIPASES. 2. Endocrine: secretes INSULIN and GLUCAGON Liver secretes into the Common Hepatic Duct Pancreas secretes into the Pancreatic Duct These 2x ducts form the Common Bile Duct which leads to --> the Duodenum In humans, the Gallbladder releases Stored Bile into the Cystic Duct

Question 33

What is the role of the gallbladder?

Answer 33

Store Bile before discharging into the duodenum via the Cystic Duct

Question 34

What body system in the Kidneys part of?

Answer 34

Renal system

Question 35

What is the role of the Kidneys?

Answer 35

part of Renal system Kidneys are found DORSAL to the peritoneal cavity, NOT IN the peritoneum, therefore described as RETROPERITONEAL Ventral surface of the kidney (Closest to the Retinal Cavity) is covered by Parietal peritoneum Dark Red colour similar to the Liver due to Rich Blood Supply Depression (HILUS) on the Medial surface is the point where the Renal ARTERY, Renal VEIN and URETER access the kidney. (only the Renal vein is obvious)

Question 36

What body system is the Urinary bladder part of?

Answer 36

Renal system

Question 37

What is the role of the Urinary Bladder?

Answer 37

Urinary bladder is On the MIDLINE Near the PELVIS a Pale Cream or Yellow bladder which STORES urine Very Thin, THREAD-like URETERS extending Anteriorly towards the Kidneys

Question 38

What body system is the Adrenal Glands part of?

Answer 38

Endocrine (adrenaline hormone)

Question 39

What is the role of the Adrenal Glands?

Answer 39

at the ANTERIOR end of the Kidney, rats have adrenal glands which are SMALL BROWN BODIES Adrenal glands are separated into 2x sections 1. Centrally, the ADRENAL MEDULLA which secretes Adrenaline 2. Surrounding the adrenal medulla is the OUTER Adrenal CORTEX (bark) that SECRETES STEROID HORMONES (e.g. Cortisol)

Question 40

Which body system is the Spleen part of?

Answer 40

Lymphatic system | clears worn out RBC and other foreign pathogens to help fight infection

Question 41

What is the role of the spleen?

Answer 41

Rat spleen = LEAF shaped organ Human spleen = FIST shaped organ found next to the Great Curvature of the stomach. also Dark Red spleen is NOT part of the digestive system, instead part of the Lymphatic system

Question 42

What are the External and Internal Female Reproductive Organs?

Answer 42

Female External Repro =3x Openings, Anterior--> Posterior Urethral O --> Vaginal O --> Anus Female Internal Repro = Rat Uterus is Y shaped due to the paired "horns" of the uterus Human Uterus is more U shaped Distal end of each horn is an Ovary which connects via Tightly Coiled Oviduct. Oviduct is difficult to distinguish from the Ovary. there are Multiple Pouches to Facilitate Numerous Births

Question 43

What are the External and Internal Male Reproductive Organs?

Answer 43

Scrotum = contains the Testes = seen near the anus Prepuce = Anterior to the scrotum (between 2nd and 3rd nipple) = skin Fold which Conceals the Glans of the Penis. Rat = Flaccid penis is contained Within (internal) the Abdominal Wall Primate = Flaccid penis is external Anus is Below base of the tail, Behind the scrotum

Question 44

What doe the Mouth consist of?

Answer 44

Rats: 3x Molar teeth on Both side of their jaw for Grinding Nostril and Mouth "tracts" join After the Palate, but divide into the Oesophagus and Trachea Trachea is Ventral to the Oesophagus

Question 45

What are the pathways of the mouth?

Answer 45

Air entering through Nasal Cavity passes VENTRALLY into the TRACHEA (blue) Food entering the Mouth passes DORSALLY into the OESOPHAGUS (pink) essentially the pathway of food entry for Air and Food entering the rat Cross Paths for Both Rats and Humans, if food doesn't cross over it enters the Trachea, we COUGH If air enters the Oesophagus, we BURP, called ERUCTATION EPIGLOTTIS= Triangular Flap, found on the Ventral side, and can COVER the opening of the Trachea (GLOTTIS), preventing Food Entry into the trachea Top of a Rat and Human mouth is Bony near the teeth and gets Softer towards the throat. 1. Hard palate (bony) = Anterior, has Grooves called Transverse Ridges, which sorts pieces of food into Various Sizes for Swallowing 2. Soft palate= No bones, More Posterior