Cancer

CANCER [MALIGNANT NEOPLASM]

Cancer is defined as any uncontrolled and unco-ordinated proliferation of cells
which invades the local tissue and metastasizes to distant organs.

The solid mass of uncontrolled cell growth is known as TUMOR.

TUMOR are of two types:

1.Benign tumors:
These are slow growing mass of neoplasm cells[cancer cells are known as neoplasm], which compresses the surrounding tissue(giving capsulated appearance) but never metastasizes to distant organs.[metastasis means lodgement or spread of neoplasmic cells to the nearby and distant organs, organs other than the origin of the tumor cells].They have good prognosis.The neoplasmic cells resemble the cells of the parent organ.As the proliferation of the cells occur by mitosis, benign tumors have fewer mitotic figures than the malignanat tumors.

2.Malignant tumors[cancer]:
These grow rapidly[NOTE: the proliferation of malignat tumor cells never exceeds than that of embryo, bone marrow or the intestinal epithelial cells], invade the surrounding tissues[grow into the surrounding tissue and deatroy them] and metastasizes to distant organs[lymph and blood are the route of metastasis, lymph being the most common route of metastasis].They usually have bad prognosis[prognosis:probability of cure and/or survival].The cells have more mitotic figures than the benign neoplasm.The cells of malignant tumor are morphologically and functionally different from the normal cells and the tumor cells are less organized than the cells of the parent organ.


Thus cancer and malignant tumor are synonyms. Its like cancer is the disease and they produce malignant tumor.Most cancer produce tumor but some like, leukemia don’t produce tumor.

The three characteristics of cancer:

1. they grow rapidly
2. they invade the surrounding tissues
3. they spread to the nearby and distant organs by help of blood or lymph, i.e. they metastasize.

Study of cancer is known as oncology.

CAUSES OF CANCER

Nearly all cancers have a genetic cause[ cancers are also known as clonal overgrowths], the proliferation is trigerred by ONCOGENES [oncogenes: genes causing cancer].Oncogenes are the activated form of proto-oncogenes i.e., proto-oncogenes are the normal version of the genes which when activated form oncogenes.Normally there are an another set of genes known as TUMOR-SUPRESSOR GENES. These prevent the cancers.When tumor-supressor genes are inactivated and proto-oncogenes activated [to form oncogenes] cancer results.


1.CARCINOGENES: THE substances or the agents causing cancer are known as carcinogens. Aflatoxins produced by Aspergillus , tobacco[tar of cigarette] ,betel nut(causes oral cancer) , smoke, , high energy radiations ( gamma rays, x-ray, uv ray and alpha particles), chemicals (benzopyrines, inhaled asbestos, cadmium, nickel ,vinyl chloride, nitrosamine, benzene etc,) , infectious agents/biological agents/pathogenes ( such as certain viruses like HPV [ human papilloma virus cause cervical cancer ], hepatitis B and hepatitis C virus causes liver cancer, Rous sarcoma virus , Epistein-barr virus and bacteria Helicobacter pylori [causes stomach cancer]).


2.HORMONAL DISBALANCE:Increased level of estrogen is associated with endometrial cancer.

3.IMMUNE-SYSTEM DYSFUNCTION:In immuneocompromised patients like in case of AIDS, a lot of malignancies are associated like Kaposis’ sarcoma and non-Hodgkin’s lymphoma.

4.HEREDITARY CAUSES:Most forms of cancer have no hereditary cause and are sporadic. However some cancers have hereditary associations.

5.AGE: The risk for cancer increases with the age.

6.ETHNICITY/ RACE:Gastric cancer is more common in Japan and Colon cancer is more common in the United States.

7.SEX

8.DIETARY HABBITS:Alcohol consumption is associated with oral and esophageal cancer.Grilled meat increases the risk of stomach cancer.

9.LIFESTYLE

[Age, sex, ethnicity, lifestyle, and dietary habbits are considered as risk factors for cancer.]


CLASSIFICATION OF CANCER

On the basis of the origin cancer is classified as:

1.CARCINOMA: Malignant tumors derived from the epithelial cells.For eg: Breast (carcinoma of breast). Liver (hepatocellular carcinoma), carcinoma of lung, carcinoma of stomach, carcinoma of colon, squamous cell carcinoma, renal cell carcinoma, carcinoma of prostrate, melanoma, seminoma [note: usually for naming benign tumor “-oma ‘suffia is added for example:lipoma is the benign tumor of fat cells, but melanoma( melanocytes), seminoma(seminiferous tubules) and thymoma (thymus) are some malignant neoplasms] thymoma, endometriod carcinoma etc. Carcinoma In Situ is the pre-malignant condition where the signs of malignancy is present but there is no evidence of invasion.i.e, CIS may transform to carcinoma.



2.SARCOMA: Malignant tumors derived from the connective tissues ( bone, cartilage, fat, muscle, blood vessles etc) Examples include: bone(osteosarcoma), cartilage(chondrosarcoma), smooth muscle(leiomyosarcoma), skeletal muscle (rhabdomyosarcoma), fat (liposarcoma) [note: liposarcoma is malignant tumor, but lipoma is benign tumor, ie usually “oma”suffix is added for naming benign tumor and “-osarcoma ia added for naming malignant tumor of connective tissue origin] , blood vessles(hemangiosarcoma), lymph vessles(lymphangiosarcoma).

3.CANCER DERIVED FROM BLOOD FORMING CELLS[HEMATOPOITIC CELLS]

LEUKAEMIA: cancer of blood or bone marrow especially that of WHITE BLOOD CELLS.

LYMPHOMA: cancer of lymphocytes . Lymphomas often originate in lymph nodes.

MULTIPLE MYELOMA: cancer of plasma cells

4.GERM CELL TUMORS:TUMORS DERIVED FROM TOTIPOTENT CELLS. Benign tumors are known as “mature teratoma” while malignant tumors are known as “immature teratoma” or “dysgerminoma”

5.BLASTIC TUMORS: Blastic tumors represent the malignant tumors resembling the immature or embryonic tissue.These are mostly common in the child hood. For eg: RETINOBLASTOMA, NEUROBLASTOMA etc.

$ The commonest cancer in childhood is ALL(Acute lymphocytic leukemia)
$The commonest cancer in the males is stomach cancer(in the world)
And lung cancer in Nepal.
$ The commenest cancer in females is breast cancer (in the world)
And cervical cancer in Nepal.


CLINICAL SIGNS OF CANCER

*local swelling, lumps, hemorrhage, pain, ulceration etc are the local signs.
*signs of metastasis: enlarged lymph nodes, hemoptysis etc.
*systemic symptoms:poor appetite, weight loss, fatigue, cachexia(wasting), night sweats, anaemia etc.

DIAGNOSIS
Cancer is diagnosed with the help of BIOPSY{REMOVAL OF THE TISSUE FOR EXAMINATION}, FNAC{FINE NEEDLE ASPIRATION CYTOLOGY}:STUDY OF CELLS..[NOTE: CERVICAL CARCINOMA IS DIAGNOSED BY PAP SMEAR-PAPALICOLAU SMEAR]

TREATMENT
1.SURGICAL EXCISION
2.RADIATION THERAPY(RADIOTHERAPY)
3.CHEMOTHERAPY/ANTI CANCER DRUGS: methotrexate, flurouracil, cisplatin etc.

The Integumentary System

INTEGUMENTARY SYATEM

[skin + derivatives = integument ]

$SKIN IS THE LARGEST ORGAN OF THE BODY/LIVER IS THE LARGEST GLAND.[JACK OF ALL TRADES== SKIN]


SKIN= EPIDERMIS [outer] + DERMIS [inner]


EPIDERMIS is ectodermal in origin.[$$ BLOOD VESSELS ABSENT IN THE EPIDERMIS]
DERMIS is mesodermal in origin.


EPIDERMIS is composed of stratified squamous epithelium, and consists of 5 layers.

1.STRATUM CORNEUM =[[$$ str. Corneum of frog contains living non-nucleated flattened cells][=è metachoresis change in skin colour in frog]] outermost layer of dead keratinized cells [keratin is a scleroprotein]. It is **thick at sole and palm. Ecdysis is shedding of stratum corneum.

2.STRATUM LUCIDUM =A thin translucent layer of dying keratinized cells which contain eleidin .*Conspicuous in soles and palms.

3.STRATUM GRANULOSUM = 2 – 4 cells deep layer, containing$ keratohyalin, conspicuous in palm and soles.

4.STRATUM SPINOSUM = CELLS ARE POLYHEDRAL

5.STRATUM BASALE = lowermost layer of columnar epithelium cells which rest on a basement membrane.divide by mitosis to form outer cells.all the keratinized structures and glands are derived from this layer.

[$$stratum spinosum + stratum basale = STRATUM GERMINATIVUM/ malpighii]

DERMIS[CORIUM]

It is a thick sheet of connective tissue present below the epidermis.About 2- 3 times thicker than epidermis.CONNECTIVE TISSUE is areolar which is dense due to abundant fibers.Blood vessels, nerve fibres, glands , muscle fibres, sanse receptors and hair follicles are present in the dermis.
$$[SENSE RECEPTORS ARE DERMAL IN ORIGIN AND HAIR AND GLANDS ARE EPIDERMAL IN ORIGIN]

$ CHROMOPHIL CELLS / MELANOCYTES produce melanin.melanocyte are present/produced in dermis but get incorporated into epidermal cells.$ albino colour /albinism:due to non-synthesis of melanin from melanocytes.[$$$ melanin synthesis: tyrosinàdopaàdopaquinoneàmelanin]

DERMIS = PARS PAPILLARIS + PARS RETICULARIS
PARS PAPILLARIS [outer]= Includes papilla and connective tissue with blood capillaries.
PARS RETICULARIS[inner] = INCLUDES lower thick connective tissue fibres with bigger blood vessels and nerves.

SENSE RECEPTORS^

1.FREE NERVE ENDINGS = SENSITIVE TO pain , touch, pressure.
2.BASKET NERVE ENDINGS / HAIR END ORGANS = TOUCH AND MOVEMENT OF OBJECTS.
3.RUFFINI’S CORPUSCLES = warmth receptors
4.KRAUSE’S END BULBS = cold sensation
5.MEISSNER’S CORPUSCLES = touch
6.PACINIAN CORPUSCLES = tissue vibrations and strong pressure
7.GOLGI-MAZZONI CORPUSCLES = heavy touch a\, pressure joint rotation
8.MERKEL’S CORPUSCLES = constant touch

[$$ VITAMIN D = Skin manufactures vit D from *cholesterol *]


GLANDS FOUND IN THE SKIN[$$ simple coiled tubular glands occur in the dermis of the skin]

1.SWEAT GLANDS = [sudoriferous glands] coiled tubular opening on the skin surface through a pore.secrets sweat [composition:H20, urea, NaCl,etc]

$SWEAT GLANDS ABSENT AT LIP TIPS IN MAN.$$ BUT IN RABBIT PRESENT ONLY ON LIPS, AND RARE ELSE WHERE.SWEAT HELPS IN LOWERING BODY TEMPERATURE]

2.OIL GLANDS/ SEBACEOUS GLANDS = flask shaped, alveolarglands opening into shaft of hair follicles and secrete oil for lubricating hair and skin.

3.lachrymal/lacrimal glands = OCCURS IN THE EYES, secrete tears

4.meibomian glands: SEBACEOUS GLANDS OPENING IN THE EYE LASHES.[ TARSAL
GLANDS/ PALPEBRAL GLANDS]

5.WAX / CERUMINOUS GLANDS = MODIFIED SWEAT GLANDS

6.MAMMARY GLANDS/MILK GLANDS = MODIFIED LOBULATED SWEAT GLANDS

7.SCENT GLANDS = MODIFIED SEBACEOUS GLANDS WHICH SECRETE $$PHEROMONES $$.========è


APPENDAGES OF SKIN-àHAIR AND CLAWS, NAILS, HOOFS FOUND IN THE SKIN.


1.HAIR: A fine kertinised filaments that develop from tubular pits known as hair follicles.Hair papilla present at the lower end of hair follicle is composed of connective tissues and nerve fibres.
Arrector pilli muscles[smooth / involuntary] are for movement of hair, $ GOOSE FLESH=èDUE TO CONTRACTION OF THESE MUSCLES IN COLD]
Bulb/root of the hair introduces new cells.
Besides bulb hair has root[inside skin] and shaf [outside skin]


2.CLAWS, NAILS, HOOFS = These are the keratinized epidermal structures developing from tips of digit.



FUNCTIONS OF THE SKIN

1.streatchable protective shield.
2.regulation of body temperature
3.sense reception
4.screen UV rays
5.synthesis of vit D
6.excretion of waste materials.


$ Body temperature is regulated by : [IOM 1995]=èskin, mouth, lungs
$The loss of heat in a spector inside cinema hall is mainly through [IOM 1995]èCONVECTION
$All of the following structures are found in the dermis except [IOM 1993]è
a.blood vessles c.sweat glands
b.sebaceous glands d.melanocytes
[ans:c]

The circulatory system - The Heart.

Circulatory system

[heart]


# Circulatory system was discovered by Aristotle.

# Closed type of circulatory syatem [blood-vascular system] was discovered by William Harvey.


Protists, porifers, coelenterates etc have a large surface area to volume ratio, so, diffusion or cytoplasmic streaming(cyclosis) is sufficient for exchange of materials between the organisms and the surrounding.
In the multicellular organisms, a specific circulatory system is needed to transport nutrients, gases, wastes, hormones etc. A typical circulatory system has 3 distinct features –
i) a circulating fluid [blood, lymph]
ii) a pumping organ [heart- human heart acts as a compression pump ]
iii)asystem op tubes through which the circulating fluid move.


TYPES OF CIRCULATORY SYSTEM

There are two types – open circulatory system and closed circulatory system.

1.Open type of circulatory system:
In open circulatory system the blood not only flows through the blood vessels but also through open spaces called lacunae and sinuses.The flow is slow and under low pressure and it is less efficient then closed type of circulatory system.this type of circulation is present in arthropods, most molluscs.

2.Closed type of circulatory system:
Blood flows in vessles only and it doesn’t come in direct contact with the tissue.The exchange of materials is mediated by INTERSTITIAL FLUID.The flow is fast and under high pressure.This type of circulation is more efficient to exchange materials as the flow is fast.Present in most annelids, cephalopods, all vertebrates, echinoderms.



Mammalian heart

The heart is a conical, muscular, hollow, mesodermal organ lying in the thorax above the diaphragm between the lungs in the middle mediastinum towards the left of the body with broad base upwards and pointed apex facing downwards.
Size of human heart: 12 cm by 9 cm by 6cm
Weight:300 gm in male, 250 gram in female.
Capacity : about 120 ml.
COVERINGS OF THE HEART:Heart is covered by a fibroserous covering known as pericardium.PERICARDIUM is composed of two layers –

1.outerfibrous layer , the fibrous pericardium, which is continuous with the tunica externa/adventitia of the blood vessles entering and leaving the heart.It prevents excessive distention of the heart.

2.inner serous layer, the serous pericardium.It is composed of two layers –the outer PARIETAL LAYER and the inner VISCERAL LAYER. The parietal pericardium is continuous with the parietal covering of the thorax .the visceral paericardium is continuous with the visceral layer of the thorax.Visceral pericardium is also known as EPICARDIUM. In between these two layers of serous pericardium is present PERICARDIAL FLUID, about 60 ml. It protects the heart from friction, mechanical shock, and external injury.

THE WALL OF THE HEART

The heart wall is composed of three layers
i) PERICARDIUM
ii) MYOCARDIUM: It is made of cardiac muscle.Cardiac muscle is involuntary musle.It has faint but regular cross-striations.It occurs as a network pattern called the syncytium.It is usually UNINUCLEATE [but sometimes binucleate].There is presence of INTERCALATED DISCS, large number of mitochondria, abundant blood supply. Contraction of these muscles help heart pump the blood..The heart starts to beat in 4th week of intra-uterine life[28 days of featal life], and continuously beat in rhythmic pattern throughout the life.THUS HEART IS SAID TO BE THE BUSIEST ORGAN OF THE BODY.The cardiac myocytes contract rhythmically and continuously.The ions required for contraction of cardiac myocytes are Na, K, and Ca.The Energy required is derived from carbohydrates (35%), aminoacids(5%), and fatty acids(60%).Automaticity/autorhythmicity, conductivity, frank-starling law[heart pumps all the blood it receives], resting membrane potential [ responsible for automaticity of cardiac muscles] of the cardiac myocytes is about -85 to -95 mV.
iii) ENDOCARDIUM: It consists of the flat epithelial cells.this layer is continuous with the endothelium of the blood vessels entering and leaving the heart.



THE HEART CONSISTS OF 4 CHAMBERS : 2 ATRIA AND 2 VENTRICLES.
THE ATRIA ARE SEPARATED FROM THE VENTRICLES BY ANNULAR PAD INTERNALLY AND EXTERNALLY THERE IS PRESENCE OF A CORANARY SULCUS.
$ THE RIGHT ATRIUM AND VENTRICLE IS ALSO KNOWN AS THE PULMONARY/VENOUS HEART.
$THE LEFT ATRIUM AND VENTRICLE IS ALSO KNOWN AS THE SYSTEMIC/ARTERIAL HEART.

THUS MAMMALIAN CIRCULATION IS CALLED AS DOUBLE CIRCULATION. DOUBLE CIRCULATION IS MORE EFFICIENT THAN TH E SINGLE CIRCULATION FOUND IN THE FISHES[ HEART OF FISHES ONLY GETS VENOUS BLOOD, HEART OF PRAWN ONLY GETS ARTERIAL BLOOD]


1.ATRIA: ATRIA gets blood from different parts of the body.The right atrium gets deoxygenated blood from all over the body and the left atrium gets oxygenated blood from the lungs.The right and left atria are separated by INTER-ATRIAL SEPTUM.There is presence of FOSSA OVALIS, which is the remnant of the FORAMEN OVALE present in the featal heart.

A) THE RIGHT ATRIUM:It gets deoxygenated blood from all over the body. The blood is carried by superior vancava and inferior vanacava. Venacava is the largest vein in the body. There is presence of EUSTACHIAN VALVE at th eopening of the inferior venacava. Superior venacava is devoid of valve[ other vein without valves are internal jugular vein, pulmonary vein and brain sinuses]. Each atrium is produced behind into a swollen flap called auricular appendage.Low muscular ridges present in the right atrium are kniwn as the MUSCULI PECTINATI/PECTINI..In the mammalian heart sinus venosus is absent.The remnant of sinus venosus is represented by SA NODE(THE PACEMAKER OF HEART). There is also an opening of CORONARY SINUS in the right atrium.(Coronary sinus drains blood from the wall of the heart), the opening of coronary sinus is guarded by,THEBESISAN VALVE.In case of rabbit there are two precaval veins(superior vanacava) and one postcaval vein(inferior venacava)
B) THE LEFT ATRIUM: It gets oxygenated blood from the lungs through 4 pulmonary veins[ the other vein carrying oxygenated blood is UMBLICAL VEIN].In casse of rabbit there are only two pulmonary veins


The right atrium communicates with the left ventricle through the tricuspid valve(as it has three cusps) ant the left atrium communicates with the left ventricle by bicuspid valve/ mitral valve(as it has 2 cucsps)These valves prevent the regurgitation of the blood back to the aria.


2.VENTRICLES:Ventricle get blood from the atrium and pumps it to other parts of the body.The right ventricle pumps to the lungs through th pulmonary trunk and the left ventricle pumps to different parts of the body.The left ventricle is at least 3 times thicker than the right ventricle.The valves between the atria and ventricles are jopined to the muscles of ventricles by chordae tendinae[cords like structures] to special muscles known as papillary muscles(conical projections).TRUNCUS ARTERIOSUS AND CONUS ARTERIOSUS ARE ABSENT IN MAMMALIAN HEART.BUT PRESENT IN HEART OF THE FROG.[FROG HAS 3 CHAMBERS- 2 ATRIA AND 1 VENTRI CLE, AND IT HAS 2 ACSSECORY CHAMBERS, CONUS ARTERIOSUS AND SINUS VENISUS]

The right ventricle pumps blood to the pulmonary artey(artey carrying impure blood), the opening of the pulmonary artey is guarded by semilunar valves(3 in number).The left ventricle pumps blood to the aorta, the opening of which is guarded by semilunar valves(3 in number)



BLOOD SUPPLY OF THE HEART: CORONARY ARTERY [first branch of aorta] supplies the oxygenated blood to the heart.CORONARY SINUS and THEBESISAN VEINS drain deoxygenated blood from the heart to the right atrium.
NERVE SUPPLY OF THE HEART: PARASYMPATHETIC SUPPLY by VAGUS NERVE.
SYMPATHETIC SUPPLY by CARDIAC NERVE PLEXUS.

CONDUCTION SYSTEM OF THE HEART:The cardiac myocytes are said to be myogenic and the mammalian heart is a myogenic heart i.e. the heart beating originates in the specializedcardiacmyocytes:the SA Node, interatrial fibres, AV Node, Bundle of his/AV Bundle, Left and Right Bundle branch and Purkinje fibres are the components of conductionsystem of heart.
SA Node is said to be the pacemaker of the heart as the heart beat originates from it. It has got highest autorhythmicity [72-80/min] but lowest conductivity [0.05m/sec]. It is situated near the opening of the superior venacava, and it is remnant of sinus venosus.
Inter-atrial fibres:These fibres carry impulses to the left atrium, so that both the atria contract together.
AV Node:It is situated at the interatrial septum near the tricuspid valve.It is said to be the PACESETTER, as it conducts impulse from atria to the ventricles.
AV Bundle/Bundle of His:It lies below the AV node and is it’s continuation.It divides to give Right and Left bundle branche.The Right bundle branch supplies the right ventricle, and the left bundle branch supplies the left ventricle.The fine branches of these which supply the ventricular wall are called the PURKINJE FIBRES, they have lowest automaticity[15-45/min] but highest conduction velocity[4m/s].BOTH THE VENTRICLES CONTRACT TOGETHER.
CARDIAC OUTPUT: It is the blood pumped by each ventricle in one minute.[The blood pumped by each ventricle in one beat is called stroke volume.it is about 70 ml]. Cardiac output is about 5L.
Cardiac Output = Stroke Volume * heart rate
=70 ml * 72 /minute
=5400 ml/min.

Cardiac output is measured by using Fick’s Principle.

Heartrate in an adult is 72 bpm(beats per minute)..The normal range is 60 – 100 bpm. Below 60 bpm is called as bradycardia and above 100 bpm is called as tachycardia.
Heartrate in fetus:140-160 bpm
Newborns:120 -140 bpm
Children:80 – 120 bpm
Heart rate is controlled by the cardiac centre in the Medulla.
HeartRate is measured clinically as pulse in the Radial artery at the wrist joint.

HeartRate Is Increased in Inspiration, Excitement, fever [ but bradycardia in Typhoid fever], exercise etc and it is decreased during expiration, fear, grief etc.


The Cardiac output Received by different organs:
Liver :25%(maximum)
Kidney:maximum CO per gram tissue weight per minute.(25%)
Brain: 25% heart:5%
20%:remaining organs


CARDIAC CYCLE:The series of electrical and mechanical events that occur in the heart in one beat. The total duration of one cardiac cycle is 0.8s.
Heartbeat has two phases : contraction phase(systole) and relaxation phase(diastole)
Atrial systole:0.1 s
Atrial diastole:0.7 s
Ventricular systole:0.3s
Ventricular diastole:0.5s

The Digestive System.

The digestive system in mammals is the only system which has two openings.
Enterology is the study of the Digestive system.

Parts & Origin of the Digestive System:
The digestive system is developmentally divided into: a) The G.I Tract. b) Associated Organs. ]

The G.I. Tract: begins from the oral cavity and ends at the anus. It is further divided into foregut, midgut and hindgut.
The foregut consists of the oesophagus, stomach and the part of duodenum upto the opening of the common bile duct (c.b.d.). The parts of the foregut are supplied by the coeliac artery. The oral cavity and the pharynx are dealt separately as pharyngeal gut.
The midgut is the part of the g.i.t. from the opening of the c.b.d. in the duodenum up till the right two-thirds of the transverse colon through the jejunum, ileum, caecum, appendix & ascending colon. The midgut is supplied by the superior mesenteric artery.
The hindgut extends from the left one-third of the colon up to the anal opening. This is supplied by the inferior mesenteric artery.

The Associated Organs of the digestive system are mainly the liver and the pancreas.

The G.I. Tract is ectodermal in origin exept the epithelial lining which is endodermal.
The parenchyma of the liver and pancreas are endodermal.

Mouth & Buccal Cavity:
The buccal cavity is lined by stratified squamous epithelium (non - keratinised).
The roof of the buccal cavity is formed by the palate. The palate is divided into two parts: the hard palate & the soft palate.
The hard palate is furthe divided into maxillary, pre maxillary & the palatine part. The hard palate is anterior to the soft palate.

The teeth are found in bothe jaws i.e. the maxilla & the mandible. It consists of the i) enamel ii) dentine iii) cement iv) Pulp cavity & v) periodontal membrane: crown, neck & root.




The dental fromula is designed to numerically denote the number & type of teeth in each half of each jaw. It is expressed as a fraction; the numerator denotes the maxilla & the denominator the mandible. The thousands' digit is the incisior, the hundreds' is the canine & so on. The dental formula in man is different for milk teeth and permanent teeth.
Milk / lacteal / deciduous teeth : 2102 / 2102; means each half of both the jaws contain 2 incisors, 1 canine, 0 premolars & 1 molar. The total milk teeth is 20.
Permanent teeth: 2123 / 2123. The total no. is 32.
In rabbits, the formula is 2033 / 1023.
An artificial set of teeth has 28 teeth.

The tongue is a muscular and movable organ. [ The diaphragm and the tongue are muscles with no skeletal attachment.]
It functions in: i) mastication ii) taste iii) phonation - i.e. speech.
The taste buds are the organ for gustation. They are principally of 4 types:
i) Circumvallate: found in the posterior aspect of tongue, arranged in a 'V' shape
ii) Filiform: no taste function, thread like.
iii) Folate: absent in man, present in rabbits.
iv) fungiform: found on the tipd and margins of the tongue.
The motor nerve supply is by the hypoglossal nerve - cranial nerve no xii.
The sensory (taste) is by the facial (vii) & the glosso-pharyngeal (ix) nerves.

The Pharynx provides the connection between the oral cavity and the oesophagus. In man it extends from the base of the skull to C-6 vertebra, about 12 cms. it is shorter in rabbits. It is a common pathway for food and for air.
It is divided into:
i) Nasopharynx : It is lined by ciliated columnar epithelium. It has the openings of the internal nares & the Eustachian tube.
ii) Oropharynx: It is lined by stratified squamous epithelium. The Waldeyer's ring i.e. formed by the palatine & pharyngeal tonsils
is present here.
iii) Laryngopharynx: It is also lined by stratifies squamous epithelium. It is continuous with the epiglottis.

Histology of the gut:

Microscopically the gut is generally divided into four distinct layers.
i) Mucosal lamina propria is the innermost layer. It consists of the columnar epithelium that lines the inside of the gut.
ii) Submucosa is the connective tissue layer next to the mucosa. It has blood vessels & nerves, the Meisseners' plexus; & the brunners glands.
iii) The muscularis layer next to the submucosa has smooth muscles arranged in two common patterns i.e. longitudinal & circular. The stomach has an exception with an innermost oblique layer also. The Myenteric & the Auerbach's plexus of nerves are located between the muscle layers.
iv) The serosa is continuous with the visceral peritoneum. The squamous epithelium is absent in esophagus & lower distal rectum & incomplete in the duodenum.

The esophagus is a 25 cm x 2 cm long muscular tube that connects the pharynx & the stomach. It has a thickest submucosa.
The upper one third is lined by stratified squamous epithelium & has voluntary muscles.
The middle one third shows transition between squamous & columnar epi.; & voluntary & involuntary muscles.
The lower one third is lined by columnar epi and has involuntary muscles.
The esophagus communicates with the stomach through the cardiac sphincter. The food bolus is moved forward by peristalsis. The peristaltic wave passes at the rate of 0.2cm - 0.5cm/sec.
The digestive glands are absent in the esophagus. The esophagus is under frequent attak from the acidic reflux from the stomach and is an important cause of esophagitis & Barett's Esophagus.

The stomach is J shaped, 25 cm long & wide bag like structure. The interior of the stomach is thrown into numerous folds of the mucosa. This is called rugae. It helps in expansion of the stomach after meals. The muscle layer is most developed in the stomach.
The mucosa contains numerous gastric glands, about 35 million in number.
The stomach is divided into 4 parts: cardiac, fundus, body & pyloric antrum. Peristalsis occurs at 2-3 min intervals.

The small intestine is divided into duodenum, jejunum & ileum. The total length in humans is around 5 metres. The S.I. has villi which are finger shaped projections of the mucosa which form the unit of absorption. Plica circularies are numerous circular infoldings of the gut throughout the S.I. The villi & microvilli with plicae increase absorption by around 600%.

The duodenum is 25 cm long. It is C or U shaped. At around the mid length, the duodenum has an opening for the common bile duct & the pancreatic duct at the Ampulla of Vater, which is guarded by the sphincter of Oddi. Villi are fewer and leaf like. Submucosal Brunner's glands which are simple branched tubular glands are present. They have goblet cells and secrete mucous. They open in the crypts of Leiberkuhn. Crypts of Leiberkuhn have 3 distinct secretions. i) glands for succus entericus / intestinal juice.
ii) Paneth cells for lysozyme.
iii) Argentaffin cells for serotonin (peristaltic stimulator), secretin (pancreas), cholecystokinin (gall bladder).

The jejunum is 2 cm long, rich in digestive glands.In comparision with ileum, it has a thicker wall, wider lumen, more vascular, and more abundant villi. Payers patches are absent. Villi have microvilli that shows brush border appearance. They show swaying type movement (segmental)
The jejunum leads to ileum. The distinguishing feature is the presence of Payers patches, i.e. lymphatic tissue found in the submucosa. might be a solitary nodule or in masses. These get infected during typhoid fever.

Motility of the gut:

The gut wall has circular and longitudinal muscles along with nerve plexus and hormones like gastrin & motilin. These help in moving the gut, essential for propelling, churning, mixing , absroption & egestion of food. The gut shows 3 types of movements.
i) Peristalsis: Wave of contractions directed proximo-distally. Occurs in proximal esophagus, stomach & intestines both L & S. Propels food forward at the rate of 0.5 - 2 cm /s. In stomach peristalsis wave occurs every 2-3 min.
ii) Segmentation movement: Stretches of the alimentary canal swell up & undergo concenteric contractions. Mixes food with digestive enzymes.
iii) Pendular: It is to and fro circular contractions, resulting in churning and mixing of food.

In rabbits the distal end of the ileum expands to form the sacculus rotundus. Fron the junction of the sacculus rotundus & large intestine arises 40 - 50 cm long tube called caecum. The largest part of the caecum is about 15 cm long called vermiform appendix. In humans the vermiform appendix is vestigeal and has lymphoid tissue. The bacretia in sacculus rotundus & caecum help in digestion of cellulose.

The large intestine: It is about 1.5 metres in humans, and around 1 m in rabbits. It begins with the caecum where the ileum ends. The patterned representation is caecum -->ascending colon-->transverse colon-->descending colon-->sigmoid / pelvic colon-->rectum-->anus.
The longitudinal muscles are not continuous in the L.I, instead they are srranged in 3 distinct bands called taenia coli. These bands are somewhat shorter than that of the intestine and thus account for the sacculated appearance called haustrations. Presence of packets of peritoneum filled with fat called appendices epiploicae. L.I. lacks villi and plicae. The sigmoid colon stores faeces.

The rectum is 75 cm long in rabbits and 13-15 cm in man. In rabbits it opens directly outside through anus which has one anal sphincter. In man there is a 4 cm long anal canal with two sphincters, the internal ( involuntary, autonomic control) & external (voluntary) anal sphincter.

The liver:

The liver is the largest organ of the human body. It is a multi-lobulated structure, in man 4 lobes :- right, left, caudate & quadrate. The right and left lobes are separated by the falciform ligament. Microscopically it is composed of hexagonal lobules, surrounded by a connective tissue sheath known as Glisson's capsule.






Functions of the liver:
i)Sectrtion of bile: non - enzymatic digestive juice.
ii) Regulates the blood sugar level. Moderator organ for homeostatic control of blood sugar by the process of glycogenesis {excess insulin - glucose --->glycogen}
Glycogenolysis {glucagon - glycogen ---> glucose }

Gluconeogenesis.
iii)Also controls lipogenesis. Excess glucose and amino acids are transformed into fats and stored in the liver cell.
iv) Excess and harmful amino acids of blood is metabolised into toxic NH3, which is again metabolised into useful ketoacids by the process of deamination in the presence of oxidase enzyme.
v) Ornithine cycle - Toxic NH3 + CO2 ------------>Urea {detoxified - excreted in urine}
vi) Haemoglobin of dead R.B.C.:-
Haemoglobin---------->Globinm + Haeme ---------> i. iron
ii. non iron---------->biliverdin-------->bilirubin -------> i.urine
ii. stool
iii. Plasma.
vii) Produces an anti coagulant heteropoly saccharide called Heparin.
viii) Prothrombin and fibrinogen are pro coagulatory proteins synth. by liver.
ix) Erythropoesis ( formation of R.B.C) in embryo.
x) As hemolytic organ
xi) Kupffer cells are liver macrophages.
xii) Site of synthesis of vit A from carotenes of carrot in the presence of enzyme carotenase.
xiii) Stores Fe & Cu as ferritin & ceruloplasmin.
xiv) Site of heat production - metabolic center
xv) Emergency storage of water.
xvi) 2nd reservoir of blood.

Physiology of Digestion
Digestion in mammals begins from the mouth. Saliva produced from the salivary glands aids this.
The saliva contains 99% water. Salivary amylase & lingual lipase are the enzymes in saliva.
Almost 1 lit. of saliva is produced each day in humans. Its pH ranges from 6.5-7.5.
Starch, sugar, glycogen ---------------------------------> Maltose, Isomaltose & limit dextrins.
(Enzyme:)Ptyalin
--> 3-4% carbohydrates
--> 30-40% starch
--> acts best in slightly
acidic pH
Stomach has specialised cells producing various enzymes and acid that helps digestion. These are:
i) Oxyntic cells / Parietal cells: These produce HCl which converts pepsinogen into pepsin. It is also antibacterial in nature. Its pH is 1.5 - 3.5. This makes the content of the stomach acidic in nature, and in reflux diseases where the gastric contents are ejected into the esophagus it is this acidity that insults the esophagus the maximum because the protective mucus is not produced.
ii) Chief / Peptic or zygomatic cells : These produce pepsinogen, which is the precursor of pepsin, the chief enzyme for protein digestion.
iii) Mucous neck cells: These produce the gastro-protective mucous.
iv) Pyloric G cells / Argentaffin cells: These produce gastrin, which incereases HCl & gastric juice secretion.

Protein Digestion:
Pepsinogen -------------------> Pepsin
(HCl )

Proteins -----------------------> Proteoses & Peptones
(Pepsin)

Milk protein in children:
Prorennin ---------------------> Rennin
(Pepsin )

Caesin ------------------------> Paracaesin
(Rennin)

Ca++ + Paracaesin -------------------------> Calcium Paracaesinate.
(Rennin )

Cal. Paracaesinate -----------------------> Proteoses & Peptones
(Pepsin)
# A small amount of gastric lipase is produced in children.

The intestine:
The pancreatic juice & the intestinal juices aid digestion in the intestine.
The pancreatic juice helps in the digestion of proteins, carbohydrates, fats & nucleic acids. 2-3 lit. of it is produced each day. It has a pH of 7.5 - 8.5.

# Protein Digestion: Trypsin in an endopeptide that is found in all animals. It breaks protein into small peptides but cannot digest keratin.
Enterokinase
Trypsinogen --------------------------> Trypsin
(Endopeptidase )

Trypsinogen --------------------------> Trypsin [autocatalysis]
(Trypsin )

Proteins, peptides, proteoses & ---------------------------------> smaller peptides
(Peptones Trypsin )

Fibrinogen ---------------------------------> Fibrin {blood clot}
(Trypsin )

#Chymotrypsin is a milk coagulating enzyme.
(Trypsin )
Chymotrypsinogen --------------------> Chymotrypsin

(Trypsin )
Proelastase ----------------------> Elastase

Procarboxypeptidase ----------------------> Carboxypeptidase.

(Carboxypeptidases )
Peptides ----------------------------------------------> smaller peptide chain + amino acids.

Fat Digestion: Steapsin / Pancreatic lipase.
Emulsified fats ----------------------------------> Tri, di & monoglycerides
Tri, Di & monoglycerides------------------------------------> fatty acids + glycerol

Carbohydrate digestion.
(sucrase )
Sucrose---------------------------> glucose + fructose

(Maltase )
Maltose --------------------------> glucose + glucose

(Lactase )
Lactose --------------------------> glucose + galactose


Absorption:
Majority of the absorption process takes place in the small intestine. Only water, alchohol & some drugs like aspirin are absorbed from stomach. Two processes are recognised:
i) Passive absorption : A slow physical process in which glucose and amino acids are absorbed by simple diffusion along the concenteration gradient. Water absorption follows by osmosis. No energy is required and it is a bidirectional process.
Fructose and mannose are absorbed with a carrier protein molecule (permease / translocase). This is also called facilitated diffusion.
ii) Active absorption: Na+, glucose, galactose and amino acids absorbed with the help pf energy provided by ATP, hydrolysis by Na+-K+ pump. Unidirectional, requires carrier molecule.
Absorption of fats: The end products of fat digestion are monoglycerides, fatty acids and glycerol. Glycerol is water soluble, so it is directly absorbed by the mucosal cells of the intestine.
In the intestinal lumen, fatty acids, monoglycerides & bile salts aggregate to form water soluble molecules called micelles. (0.03-4nm diam.) Each micelle has bile salts, in its outer part & the hydrophobic fatty acids and cholesterol form the core. this action of bile salts is called HYDROTROPHIC ACTION. Micelles are taken up by pinocytosis.
In the mucosal cell, fatty acids & monoglycerides are again formed into triglycerides.
Neutral fat so formed are surrounded by a coat of B-lipoprotein to form water soluble globules called chylomicrons.

Short chain fatty acids ( less than 14 carbon atoms) are directly absorbed into portal circulation. Bile salts are also extracted by liver through portal circulation. This is the entero-hepatic circulation of bile salts.

Past questions in I.O.M entrance from digestive system:
1) A dental plaque tends to form rapidly: (2004)
a.while eating b.just before brushing teeth c.during sleep d. at a constant rate.
Ans: b.

2) Which of the following is not produced in man: (1998)
a. Somatostatin b.serotonin c. chymosin d. adrenaline.
Ans: c

3) The pH of saliva is about: (1995)
a. 1.5 b. 3.5 c.6.8 d.7.4
Ans: c

4) E.coli is the normal flora of: ( 1994/95)
a. colon b. intestine c.ileum d.stomach
Ans: a

5) Salivary gland which opens in the floor of the mouth on either side of the frenulum of tongue is: (1995)
a. Parotid b. Sub-mandibular c. sub-lingual d. none
Ans: b

6) Which of the following is a mucus generating factor: (1995)
a. excessive heat and cold b. corosion by chemical
c. irritant gas chemicals d. all of the above
Ans: d

7) Which of the following organ is non functional in humans: (1993)
a.Pinna b. vermiform appendix c. wicdom teeth d. all
Ans: d

8) Jaundice is caused by malfunction of: (1999)
a. Pancreas b. liver c. kidneys d. spleen
Ans: b

9) One feels drowsy after meal because ( 1993)
a. Increased b.p. b. decreased blood supply to the brain
c. increased body wt. d. reduced blood supply to the intestine
Ans: b

10) Iron is absorbed from: (2005)
a. ileum b. jejunum c. duodenum d. caecum
Ans c

11) The dental formula for permanent teeth is: (1993)
a) 2102 b.2123 c. 2321 d. 2033

12) Gastric acid secretion is stimulated by: (1993)
a. food in the mouth b. histamine c. gastrin d. all


13) Brunner's glands are characteristic of (1993)
a. stomach b. duodenum c. ileum d. jejunum.
Ans: b

14) The detoxification/ metabolism of drugs takes place in the: (1993 ,2003)
a. liver b. blood c. brain d. kidneys
Ans: a

15) Which of the following is not the function of liver: (2005)
a. Bile formation b. dogestion of proteins c. urea formation d. plasma protein synthesis.

16) The amount of bile secreted per day os about: (1994)
a. 500 ml b. 100 ml c. 1000 ml d. 10 ml
Ans a

17) Gall bladder and: (1997)
a. Insulin b. Gastrin c. cholecystokinin d. serotonin
Ans: c

18) Water is mainly absorbed from (1996/ 1998)
a. Duodenum b. Small intestine c. stomach d. colon
ans: b

19) The organ known as reservoir of stool is: (1997)
a. sigmoid colon b. rectum c. caecum d. vermiform appendix.
Ans: a

20)The organ rudimentary in man but functional in animals is: (1995)
a.ileum b. caecum c. appendix d. anus
ans: c

21) Vermiform appendix in humans may play a part in:
a. digestion b. hormone synthesis c. immune system d.enzyme secretion
Ans c

22) Cholecystectomy is:
a. surgical removal of gall bladder b. gall bladder stones
c. gall bladder cancer d. gall bladder inflammation
Ans: a

23) A congenital anomaly in which upper lip has a distinct cleft is called:
a. hare lip b. mouse lip c. rat lip d. rodent lip
Ans a

24) Maximum energy is obtained from the oxidation of:
a. Fat b. Carbohydrate c. Protein d. Alchohol
Ans a

25) Which of the following is non functional in man:
a. 3rd molar b. 2nd molar c. incisor d. premolar]
Ans:a

26) Alchohol absorption takes place mainly in:
a. ileum b. duodenum c. liver d. stomach
Ans d

27) The longest part of alimentary canal is:
a. esophagus b. stomach c. ileum d. colon
Ans c

28) Laxatives are used for the treatment of:
a. diarrhoea b. constipation c. piles d. vomiting
Ans b

29) Which of the following is not the part of large gut:
a. ileum b. rectum c.caecum d. vermiform appendix
Ans a

30) The first permanent tooth erupts at the age of:
a. 2 yrs b. 4 yrs c. 6 yrs d. 7 yrs
Ans c

31)The number of molars in an adult aged 40 yrs is:
a. 10 b. 12 c 14 d. none
Ans b

32)Dental carries is caused by:
a.bacteria b. viruses c. fungus d. food particles
Ans a

33)In liver energy is stored in the form of:
a. glucose b. glycogen c. sucrose d. fructose
Ans a

34) The sodium absorption in intestine is mainly by the process of :
a. active transport b. diffusion c. passive transport d. facilitated diffusion
Ans:

35) In which of these disease Vit B12 is not absorbed from the intestine:
a. Iron def. anemia b. Pernicious anemia c. thallasemia d. Spherocytosis

36) Starch is digested by:
a. Maltose b. Invertase c. Diastase d. sucrase
Ans c.