Communicable Diseases

Communicable Diseases

An infectious disease which gets transferred from infected person to other persons by direct or indirect means is called a communicable disease.

Infection:

Successful entry of a pathogenic microorganism capable of inducing a disease into systemic circulation is called an infection.

Causative Organism:

Microorganism responsible for inducing a disease is called as “Causative organism”.

Vector: 

It is an organism who itself doesn't cause the disease but transfers the pathogen from one host to another host.

E.g. Mosquitos in Malaria.

Measles

Other Names:

Rubella

खसरा

Causative Organism:

Measles RNA paramyxo‐virus i.e. (Rubella virus).

Mode of Transmission: 

• Directly from person to person by droplet infection & droplet nuclei.
• Entry of portal respiratory tract.
• Rarely through conjunctiva.

Symptoms:

• cough
• fever
• runny nose
• red eyes
• sore throat
• white spots inside the mouth
• Widespread Skin rashes

Prevention & Control: 

• Immunization‐95%
• Measles Vaccination 
• Unvaccinated children immunized by immunoglobulin.
• Paracetamol is used to reduce body temp.
• Strict Isolation

Diphtheria

Causative Organism:

Corynebacterium diphtheriae

Mode of Transmission:

• By droplet infection
• Directly from infected cutaneous lesions
• Transmission by objects like toys,cups etc.
• Portal of entry is mainly the respiratory tract.

Symptoms:

• A thick, gray membrane covering your throat and tonsils
• A sore throat and hoarseness
• Swollen glands (enlarged lymph nodes) in your neck
• Difficulty breathing or rapid breathing
• Nasal discharge
• Fever and chills
• Malaise

Prevention & Control:

• Strict Isolation.
• Early detection of carriers & their treatment.
• Active immunization combined with DPT vaccine.
• Antibiotics like Penicillins, Erythromycin.

Tuberculosis

Causative Organism: 

Mycobacterium tuberculosis

Mode of Transmission:

• It is mainly transmitted by droplet infection and droplet nuclei. 
• The most common source is the sputum of the patients with pulmonary tuberculosis.
• Coughing can produce a large number of droplets. Fresh droplets carry viable organisms. (The frequency and vigor of cough and the ventilation of the environment influences the transmission of infection.)
• It can thrive in organs of relatively high oxygen tension such as apices of the lung, the renal parenchyma, the growing ends of the bones and the cerebral cortex.
• It is also tolerant to the acid environment of the stomach and it has been isolated from the gastric contents of the patients suffering from tuberculosis.

Symptoms:

• Coughing that lasts three or more weeks
• Coughing up blood
• Chest pain, or pain with breathing or coughing
• Unintentional weight loss
• Fatigue
• Fever
• Night sweats
• Chills
• Loss of appetite

Prevention & Control:

• One should live in a properly ventilated house.
• Nourishing and well balanced diet should be taken.
• Milk should be consumed after proper, boiling.
• Tuberculosis patients should be detected as early as possible by microscopic examination of sputum, chest x-ray and tuberculin test.
• Infected persons should be isolated.
• Detected patients should be promptly treated with specific anti-tubercular drugs.
• Patients should be advised to spit only in sputum cup containing disinfectant,
• While coughing he should use a handkerchief, which should be properly disinfected after use.
• B.C.G, vaccination (Bacillus Calmette Guerin) should be given to newborns below four weeks of age.
• Vaccination can be done to individuals below 20 years of age.
• People should be taught that tuberculosis is not an incurable disease. They should be advised that taking the antituberculosis drugs in sufficient doses and for a sufficient period of time is very essential for the complete cure of the disease.

Treatment:

• It requires long term treatment with multiple drugs so as to avoid resistance.
• Drugs like Isoniazid, Pyrazinamide, Ethambutol
• Antibiotics like Minocycline, Streptomycin, Rifampicin.

Polio

Causative Organism: 

A poliovirus which has three serotypes 1, 2 and 3.

Mode of Transmission:

• Faeco-oral route is the main route of transmission of the disease. Man is the reservoir of the virus.
• Another route is the droplet infection, this occurs in the acute phase of disease when the virus occurs in the throat. 
• Close personal contact with an infected person facilitates droplet infection.

Symptoms:

• Fever
• Sore throat
• Headache
• Vomiting
• Fatigue
• Back pain or stiffness
• Neck pain or stiffness
• Pain or stiffness in the arms or legs
• Muscle weakness or tenderness

Prevention & Control:

• Notification of the case to the health authorities.
• Proper disposal of urine and faeces. 
• Protection of water sources and supply of safe drinking water. 
• Personal hygiene should be strictly maintained.
• Poliovirus vaccine live oral (Trivalent oral polio vaccine, Sabine vaccine) is the vaccine of choice for primary Immunization of children. 
• It is indicated for active immunization against infections of poliovirus caused by type 1, 2 and 3 in infants starting at 6-12 week.

Cholera

Causative Organism:

A bacteria called Vibrio cholerae

Mode of Transmission: 

• Spread is mainly by contaminated food, water, milk. 
• Human beings are the only reservoir of cholera infection.
• Immediate source of infection is the stools and vomitus of cases and carriers.

Symptoms:

• Diarrhoea
• Nausea
• Vomiting
• Electrolyte imbalance

Prevention & Control:

• Early detection of suspected cases and Bacteriological examination of stools for confirmation.
• Cholera cases should be notified to the local health authority.
• Patient's stools, vomitus should be collected in a pot containing disinfectant.
• Water and milk should be consumed only after boiling.
• Fruits, vegetables should be thoroughly cleaned before use
• Strict isolation.

Treatments:

• Oral rehydration therapy.
• IV fluids.
• Rehydration is the key to save life.
• Antibiotics like Ciprofloxacin, Doxycycline.

Typhoid

Causative organism:

Salmonella typhi

Salmonella para typhi‐ A

Salmonella para typhi‐ B1

Mode of Transmission: 

• Faecal‐Oral route
• Urine‐ Oral route
• Direct transmission through contaminated hands or fingers.
• Indirect transmission through contaminated water, milk, food or through flies.

Symptoms:

• poor appetite;
• abdominal pain and peritonitis;
• headaches;
• generalized aches and pains and weakness;
• high fever, often up to 104 F;
• lethargy (usually only if untreated);
• intestinal bleeding or perforation (after 2-3 weeks of the disease);
• Cough;

Diagnosis: 

Microscopic testing of blood, urine, feces.

Prevention & Control: 

• Control of reservoir.
• Sanitation.
• By immunization   TAB vaccine‐S. typhi,S. paratyphiA, S. paratyphi B
• Oral typhoid vaccine 
• Anti typhoid vaccine

Treatment:

• Antibiotics like Ciprofloxacin, Azithromycin.

Filariasis

Causative Organism:

nematodes :

1)W. Bancrofti

2)B. Malayi

3)B. Timosi

Mode of Transmission: 

• By bite of infected mosquito

Symptoms: 

• Fever.
• Inguinal or axillary lymphadenopathy.
• Testicular and/or inguinal pain.
• Skin exfoliation.
• Limb or genital swelling

Prevention & Control:

• By vector control:‐ Elimination of breeding places of mosquitoes by sanitation & waste water disposal.
• Chemotherapy – Diethylcarbamazine (DEC)

Trachoma

Causative organism:

Bacteria Chlamydia trachomatis

Mode of Transmission:

• It occurs by direct or indirect contact with ocular discharges of infected people or fomites. 
• Swimming pools where water can get contaminated is also a source of infection.
• Overcrowding also helps in transmission

Symptoms:

• Mild itching and irritation of the eyes and eyelids
• Discharge from the eyes containing mucus or pus
• Eyelid swelling
• Light sensitivity (photophobia)
• Eye pain

Prevention & Control:

• Early diagnosis and treatment of cases.
• Common use of eye cosmetics like kajal, surma should be avoided.
• Health education and community hygiene plays an important role in prevention and control of trachoma.
• Strict isolation.

Treatment:

• Ciprofloxacin eye drops
• Azithromycin eye drops
• Chloramphenicol eye drops

Leprosy

Causative Organism:

A bacteria “Mycobacterium leprae”

Mode of Transmission:

• Leprosy may be transmitted by droplet infection, direct or indirect contact of an infected patient. 
• It may be transmitted through breast milk of lepromatous mother, by insect vectors or by tattooing needles.

Symptoms:

• the appearance of skin lesions that are lighter than normal skin and remain for weeks or months
• patches of skin with decreased sensation, such as touch, pain, and heat
• muscle weakness
• numbness in the hands, feet, legs, and arms, known as “glove and stocking anesthesia”
• eye problems
• enlarged nerves, especially in the elbows or knees
• stuffy nose and nosebleeds
• curling of the fingers and thumb, caused by paralysis of small muscles in the hand
• ulcers on the soles of the feet.

Detection of the cases:

Lepromin Skin Test

Prevention & Control: 

• Detection of the cases.
• Multidrug therapy for control and cure.
• Surveillance
• Immunoprophylaxis
• Chemoprophylaxis and rehabilitation of patients
• To interrupt the transmission of the disease.
• Treat the patient for complete cure and rehabilitation..
• Isolation of patients.

Treatment:

• It also requires long term treatment with multiple drugs to avoid resistance.
• Drugs like Dapsone, Solapsone, Clofazimine.
• Antibiotics like Streptomycin, Rifampicin, tetracycline

AIDS

(Acquired Immunodeficiency Syndrome)

Causative Organism:

Human Immunodeficiency Virus (HIV)

Mode of Transmission:

• HIV is transmitted from person to person by Sexual contact: Any vaginal, oral or anal sex with infected partner can spread AIDS, as the virus is present in the vaginal secretions, semen.
• Transfusion of the infected blood or through contaminated needles and syringes.
• The virus can be transmitted from the infected mother to foetus through the placenta.

Symptoms:

• Fever
• Headache
• Muscle aches and joint pain
• Rash
• Sore throat and painful mouth sores
• Swollen lymph glands, mainly on the neck
• Diarrhea
• Weight loss
• Cough
• Night sweats

Diagnosis:

• ELISA (Enzyme Linked Immunosorbent Assay)
• Western Blot Method.

Prevention & Control:

• Screening of blood donors for AIDS.
• Screening of high risk groups like drug addicts and prostitutes.
• Avoid indulgence in multiple sexual partners, avoid oral, anal sex.
• Use of contraceptive devices like condoms.
• Use of disposable syringes and needles.

Treatment:

• Antiviral drugs like Lamivudine, Zidovudine.
• Immunomodulators.
• Symptomatic.

Syphilis

Causative Agent:

A spirochaete bacteriumTreponema pallidum

Symptoms:

• Unusual discharge, sore/rash usually in groin area.

Mode of Transmission:

• Sexual contact with an infected person.
• Affected mother to child.

Prevention & Treatment:

• Avoid unsafe sexual contact
• Use of condoms.
• Penicillin 600000 units/day

Gonorrhoea

Causative Organism:

Gonococcal-Neisseria gonorrhoea

Mode of Transmission:

• Sexual contact with an infected person.
• Affected mother to child.

Symptoms:

• Painful urination
• Pus-like discharge from the tip of the penis
• Pain or swelling in one testicle
• Increased vaginal discharge
• Painful urination
• Vaginal bleeding between periods, such as after vaginal intercourse
• Abdominal or pelvic pain

Prevention & Treatment:

• Single I.M.injection of  600,000 Units of procaine penicillin is in most instances sufficient.
• Avoid unsafe sexual contact
• Use of condoms.

With Special Thanks to Prof. Pravin Awate.

Special Sense Organs

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 Special Sense Organs:

Introduction:

The special senses include sense of smell, taste, hearing, vision and touch.

A) Sense of smell 

• The sense of smell or olfaction originates in the superior part of the nasal cavity.

• The nose contains 10-100 millions receptors for the sense of smell.

• Olfactory receptors react to odorant molecules in inspired air of the nasal cavity. 

• The sense of smell may affect the appetite. If the odours are pleasant the appetite may improve and vice versa. 

• From the olfactory portion of nasal cavity nerve fibres pass through the cribriform plate of the ethmoid bone to the olfactory bulb. From this region nerve fibres are passes to the olfactory area in the temporal lobe of the cerebral cortex. In this area the impulses are interpreted and odour perceived.

• ‘Sniffing’ concentrates more molecules in the roof of the nose. This increases the stimulation of olfactory receptor and the perception of the smell.

B) Sense of taste (gustation)

• Tongue consists of about 10000 taste buds. 

• The taste buds are present in elevations on the tongue called papillae. 

• There are three types of papillae.

1) Vallate papillae 

2) Fungiform papillae

3) Filiform papillae

 

1) Vallate papillae 

• About 12 large, circular papillae form an inverted V-shaped row at the back side of the tongue. 

• Each of these papillae consist of 100-300 taste buds.

2) Fungiform papillae

• It is mushroom shaped elevations scattered over the entire surface of the tongue. 

• Each papilla consists of 5 taste buds.

3) Filiform papillae

• These are thread like structure which increases friction between the tongue and food. 

• It also facilitates movement of food in the oral cavity.

Tastes:

• Five primary tastes can be distinguished as sour (आंबट) , sweet (गोड), bitter (कडू), salty (खारट) and umami (तुरट) (meaty/savory). 

• All other tastes are a combination of the two or more of the five primary tastes or are associated with olfactory sensation (smell). 

• Certain chemicals stimulate gustation receptors.  

• Nerve impulses are generated and conducted towards the taste area in the parietal lobe of the cerebral cortex where the taste is perceived.

• The stimulation of different tastes takes place at different parts of the tongue.

1) Sweet and salty taste mainly at the tip of the tongue.

2) Sour taste at the sides of the tongue.

3) Bitter taste at the back of the tongue.

4) Umami taste at the several regions of the tongue.

C) Hearing 

• The organ of hearing is ear. 

• It is supplied by VIIIth cranial nerve (Vestibulocochlear Nerve), which is stimulated by vibrations of sound waves.

• The ear is divided into three main regions.

1) External (outer ear)    

2) Middle ear        

3) Internal ear

1) External (Outer ear)   

• The external ear consists of the auricle (pinna), external auditory canal and eardrum (tympanic membrane).

• The auricle is made up of elastic cartilage which is covered by skin. 

• The external auditory canal is a curved tube about 2.5 cm long and extends from the auricle to the eardrum. 

• The eardrum is a thin, semi transparent part present in between the external auditory canal and middle ear.

 

2) Middle ear

• The middle ear is the small cavity present in the temporal bone. 

• The anterior wall of the middle ear contains an opening that directly connects with the nasopharynx called as auditory tube (Eustachian tube). 

• Middle ear consists of three smallest bones present in the body called auditory ossicles. 

• The three bones are the malleus, incus and stapes. 

• The one end of the malleus is attached to the internal part of eardrum. 

• The other end of the malleus articulates with the body of incus. 

• The incus articulates with the head of the stapes. 

• The base of the stapes fits into the oval window. 

• Below the oval window is another opening called the round window.

Internal structure of Ear

 

3) Internal (Inner) ear

Structurally the internal ear consist of two main divisions,

a) The bony labyrinth :

• It is a series of cavities present in the temporal bone. 

• It consists of a fluid called perilymph. 

• It is divided into three areas.

i) The semicircular canals - 

• They are anterior, posterior and lateral semicircular canals. 

• Each canal consists of a swollen enlargement at one end called the ampulla. 

• It contains receptors for equilibrium. 

ii) The vestibule - 

• It is the oval central portion of the bony labyrinth. 

• It also contains receptors for equilibrium.

iii) The cochlea - 

• It continues with the vestibules. 

• It is a bony spiral canal like a snail shell and makes almost three turns around a central bony core. 

• The cochlea contains receptors for hearing.

b) Membranous labyrinth –

• These are the series of tubes present inside the bony labyrinth. 

• It is lined by epithelium and contains a fluid called endolymph.

Physiology of hearing:

• The auricle directs the sound waves into the external auditory canal. 

• These sound waves strike the eardrum and cause the eardrum to vibrate back and forth. 

• The vibration is transmitted from the eardrum to the malleus to the incus and then to the stapes. 

• The vibrations from the middle ear are transferred to the perilymph. 

• From the perilymph the vibrations are transmitted to the endolymph, which leads to the generation of nerve impulses. 

• The generated nerve impulses pass to the auditory portion of the cerebral cortex. 

• These impulses of hearing are interpreted by the brain.

D) Vision

• The eye is the organ of vision (sight) present in the orbital cavity. 

• The adult eyeball measures about 2.5 cm in diameter. 

• The wall of the eyeball consists of three layers.

1) The superficial fibrous layer

• It consists of the anterior cornea and posterior sclera. 

• Cornea is transparent layer which covers the coloured iris. 

• The sclera is the ‘white’ of the eye. 

• The sclera covers the entire eyeball except the cornea and gives shape to the eyeball. 

• An opening is present at the junction of the sclera and cornea called scleral venous sinus. 

• A fluid called aqueous humour drains into this sinus.

• The lacrimal caruncle, is the small, pink, globular nodule at the inner corner of the eye. It is made of skin covering sebaceous and sweat glands.

  The front view of Eye

2) The middle vascular layer

• It consists of three parts: choroid, ciliary body and iris.

• Choroid consists of various blood vessels which gives nutrients to the posterior surface of the retina. 

• It also contains melanocytes that produce the pigment melanin which prevents reflection and scattering of light within the eyeball.

• The anterior portion of the choroid becomes the ciliary body. 

• The ciliary body consists of ciliary processes and ciliary muscle. 

• The ciliary processes contain blood capillaries which secretes aqueous humour.

• The ciliary muscle is a circular band of smooth muscle. 

• Contraction and relaxation of the ciliary muscle changes the shape of the lens for near and far vision.

• Iris is attached to the ciliary processes, present in between the cornea and the lens. 

• Iris consists of melanin which determines the colour of the eye. 

• The opening in the centre of the iris is called the pupil.

Section of Eyeball

3) The inner nervous layer

• The inner layer of the eyeball is the retina which covers the posterior part of the eyeball. 

• It is a very delicate structure and responsible for stimulation by light rays.

• It consists of several layers of retinal neurons. 

• The light sensitive layer consists of sensory receptor cells namely rods and cones. 

• The rods and cones are specialised cells which converts light rays into nerve impulses. 

• Rods stimulate in dim light and do not produce colour vision while cones stimulates in bright light which produce colour vision.

 

Interior of the eyeball

• The lens divides the interior of the eyeball into two cavities: the anterior cavity and vitreous chamber.

• The anterior cavity consists of two compartments namely the anterior and posterior chamber. 

• The anterior chamber present in between the cornea and the iris. 

• The posterior chamber present in between the iris and lens. 

• Both the chambers are filled with a watery fluid that nourishes the lens and cornea called aqueous humour.

• Vitreous chamber is present in between the lens and the retina. 

• It consists of colourless, transparent, jelly like substance called vitreous body.

• It maintains intraocular pressure and prevents the wall of the eyeball from collapsing.

E) Touch 

• The skin is the organ of sensation of touch. 

• The skin covers the external surface of the body and it is the largest organ of the body. 

• It consists of two layers: epidermis and dermis and accessory organs like hair, nails, sebaceous glands, and sweat glands.

1) Epidermis

• The epidermis is made up of keratinized stratified squamous epithelium which produces the protein keratin. 

• Keratin is a tough fibrous protein which protects the skin and underlying tissues from heat, chemicals and microbes. 

• Epidermal cells consist of melanocytes which produce the pigment melanin.

• Melanin is responsible for skin colour and absorbs ultraviolet (UV) light.

• In most of the body regions epidermis has four layers: stratum basale, stratum spinosum, stratum granulosum and a thin layer of stratum corneum. This is called ‘thin skin’. 

• In the fingertips, palms and soles, the epidermis has five layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum and a thick layer of stratum corneum. This is called ‘thick skin’.

2) Dermis

• The dermis is made up of connective tissue. 

• Dermal tissue consists of blood vessels, nerves, glands and hair follicles. 

• The dermis is divided into a papillary region and a reticular region. 

• The papillary region consists of areolar connective tissue with fine elastic fibres.

• The reticular region consists of fine dense irregular connective tissue with collagen fibres and some elastic fibres. 

• It also consists of adipose tissues, hair follicles, nerves, sebaceous (oil) glands and sweat glands. 

• Sebaceous glands of the skin open into the hair follicle. 

• These glands are absent in the palm and sole region. 

• Sebaceous glands secrete some oily secretions called sebum. 

• The sebum keeps skin soft and smooth. It also acts as bactericidal agent which prevents infection by microorganisms.

Functions of the skin

1) The skin regulates body temperature by liberating sweat at its surface and by adjusting the flow of blood in the dermis.

2) The dermis of the skin consists of extensive network of blood vessels and act as blood reservoirs. 

3) It provides protection to the body.

4) Cutaneous sensations of the skin are responsible for sensations like touch, pressure, vibration, temperature and pain.

5) Elimination of some substances from the body.

6) The skin acts as absorption medium i.e. the passage of material from the external environment into the body.

7) Synthesis of vitamin D by the ultra violet rays of the sun takes place in the skin.

Physiology of pain

• Pain serves a protective function by signalling the presence of tissue damaging conditions. Indication of the location of pain may help the underlying cause of disease.

• Nociceptors (Noci-harmful) are the receptors for the pain which are free nerve endings present in every tissue of the body except the brain. 

• Intense thermal, mechanical and chemical stimuli can activate nociceptors.

• Tissue irritation and injury release chemicals such as prostaglandins, kinins and potassium ions that stimulate nociceptors.

• Conditions that generate pain include excess stretching of any structure, prolonged muscular contraction, muscle spasm etc.

 

QUESTIONS

1. Give the functions of tongue.

2. What are the fundamental sensations of taste?

3. Explain in short V.S. of human skin.

4. Describe the functions of skin.

5. Draw and label diagram of eye.

6. Explain the physiology of pain.

7. Explain mechanism of hearing in short.

8. Explain physiology of taste.

9. Draw and label structure of ear.

10. Write a short note on eye.

 

Digestive System

Introduction: 

• Digestion is the process of breaking large and complex food molecules into smaller and simple molecules easy for absorption, with help of digestive enzymes and acid.
• Like other systems of the body Digestive system also works in coordination with other systems.
• The branch of science that deals with the structure, function, diagnosis and treatment of diseases of stomach and intestine is called Gastroenterology.

Digestive System:

• It consists of,
  • Gastrointestinal Tract (Alimentary Canal):
    • Mouth,
    • Pharynx,
    • Oesophagus,
    • Stomach,
    • Small Intestine.
    • Large Intestine.
  • Accessory Organs:
    • Teeth,
    • Tongue,
    • Salivary Glands,
    • Liver,
    • Gallbladder and Pancreas.

Activities of Digestive System:

• Digestive system performs following major activities,
  • Ingestion: Eating
  • Movement of Food: Through peristalsis from mouth to anus.
  • Digestion: Chemical and Mechanical
  • Absorption: 
  • Defecation: Elimination of undigested waste.





Alimentary Canal:

• Alimentary canal is made up of ‘Four Types” of layers throughout its length.
• These layers are,
  • Mucosa.
  • Submucosa.
  • Muscularis.
  • Serosa. 
• These layers are in continuation with mesentery ( Double fold of peritoneal layer)
• Mucosa: 
  • It is also referred to as “Mucous Membrane” as mucous production is one of its main functions.
  • It is made up of three sub layers,
    • Epithelium
    • Lamina propria.
    • Muscularis mucosa.
  • Mouth, Phyrenx, Oesophagus and anal canal contains Squamus stratified epithelium.
  • Stomach and intestines contain Columnar epithelium off which some are modifies to “Goblet Cells” which secrete mucus.
  • Lamina propria contains some connective tissue and is associated with lymphocytes and forms MALT ( Mucosa associated Lymphoid Tissue) which protects from food borne infections.
  • Muscularis mucosa is a thin layer of smooth muscles responsible for folding of the stomach and intestinal tissues.
• Submucosa:
  • It is a broad layer of connective tissues consisting of blood vessels and nerves.
  • It also contains glands that secrete digestive enzymes.
• Muscularis:
  • Third layer is also called “Muscularis externa”.
  • It is a muscular layer that imparts mechanical digestion.
  • In the upper and lower part it is made up of skeletal muscles providing voluntary control on digestion and evacuation.
  • In intestines it is double layer while in stomach it is three layered.
• Sclerosa: 
  • Present only on organs inside the abdominal cavity.
  • Made of a layer of visceral peritoneum and a loose connective tissue.
  • Main function is to keep organs in position.
  • Instead of Serosa the mouth, pharynx and oesophagus contains a dense sheet of collagen fibers called adventitia.

Stomach:

• Stomach is present between Oesophagus and First part of small intestine i.e. duodenum.
• It is a “J” shaped organ present on the left side of the body and just below the diaphragm.

  

  
• It is divided into “Four” parts as follows,
  • Cardia: Superior opening, contains “Cardiac Sphincter”. 
  • Fundus: Superior rounded portion.
  • Body: Central portion below fundus.
  • Pylorus: last part, below body, made up of two parts,
    • Pyloric Antrum:
    • Pyloric canal: It contains “Pyloric Sphincter”.
• Cells of Stomach:
  • Mucous cells: secrete mucus that protects against stress and acid.
  • Parietal cells: secrete hydrochloric acid
  • Chief cells: secrete pepsin, a proteolytic enzyme
  • G cells: secrete the hormone gastrin
• Functions of Stomach:
  • Reservoir of food.
  • Secretes gastric acid.
  • Gastric acid aids in the process of digestion.
  • Acidic pH in the stomach kills the microbes present in the food.
  • The churning movements of the stomach cause mixing of food with gastric juices.
  • The pepsin present in gastric juice helps in protein digestion.
  • The gastric lipases start digestion of fats.
  • Acidic drugs like Aspirin get absorbed from the stomach.
  • Mucosal membrane and mucus of stomach protects linings of stomach from gastric acid.
  • Cardiac sphincter prevents reflux of acidic contents in oesophagus.
  • Pyloric sphincter regulates entry of chyme in small intestine and reverse entry into the stomach.

Small Intestine:

• It is present between the stomach and large intestine.
• It starts at duodenum and ends at ileocaecal junction.
• It lies in the abdominal cavity surrounded by large intestine.
• Length is  5 Meters and diameter is 1.5 inches.
• Provides Chemical as well as mechanical digestion.
• Main site for chemical digestion and absorption of food.
• Contains “Three” parts,
  • Duodenum.
    • First part.
    • Starts near the pyloric sphincter of stomach.
    • “C” shaped.
    • Smallest part is only 25 cm.
    • Contains openings of bile duct and pancreatic duct.
    • It has little acidic pH.
  • Jejunum.
    • Middle part.
    • Present between duodenum and ileum.
    • 3 Feet in length.
  • Ileum.
    • Last part.
    • Starts after jejunum and ends at large intestine at “Ileocaecal Junction”.
    • Contains ileocaecal sphincter.
    • 6 feets in length.
• Cells of Small Intestine:
  • Absorptive Cells:
    • Modified columnar epithelium.
    • Contains “Microvilli '' provides greater surface area.
  • Paneth Cells:
    • Secrete antimicrobial substances.
    • Protects from microorganisms survived from stomach acid.
  • Enteroendocrine Cells:
    • Cells with endocrine functions.
    • S cells : Secretin (Regulates secretions of Pancreas and Liver.
    • ICells: Secretes Cholecystokinin (Regulate secretion of Bile.)
    • K Cells: Secrete a glucose dependent peptide that stimulates secretion of insulin.
    • G Cells: Secrete “Gastrin”. (Stimulates Gastric Acid Secretion).
  • Goblet Cells: Secrete Mucus.
• Functions of Small Intestine:
  • Forward movement of food by peristalsis governed by ANS.
  • Secretion of Intestinal Juice, (Governed by ANS).
  • Absorption of nutrients and Vitamins.
  • Secretion of Secretin and Gastrin.
  • Mechanical and Chemical Digestion.
• Movements of Small Intestine:
  • Small intestine shows two types of movements,
    • Peristalsis.
    • Segmentation.
  • Peristalsis:
    • It is a spontaneous contraction and relaxation of “Longitudinal Muscles”.
    • Results in forward movement of food.
    • It is in single direction i.e. towards anus.
    • Controlled by “ANS” (Ach increases while Adr decreases).
  • Segmentation: 
    • It is a spontaneous contraction and relaxation of “Circular  Muscles”.
    • Results in forward and backward movement of food.
    • It is in two directions.
    • Not controlled by ANS, it is Myogenic in nature.
  • “Watch This Video”.

Large Intestine.

• Last part of G.I.T.
• Length is about 5 Foot and diameter increases from Caecaum to Anus.
• In fact length is very less as compared to small intestine but called as Large intestine because of its bigger diameter.
• It is present around the small intestine and forms a frame around it.
• It is divided into following parts;





• Caecum.
• Ascending Colon.
• Transverse Colon.
• Descending COlon.
• Sigmoid Colon.
• Rectum.
• Anal Canal.

Caecum:

• First part of large intestine.
• Starts at “Ileocaecal Junction”.
• Ileocaecal sphincter is present in caecum.
• Caecum has a small twisted coiled tubule called “Appendix”.
• It ends at “Ascending Colon”.

Ascending Colon:

• Remaining part after caecaum is called “Colon”.
• Ascending colon is the first part of the colon.
• It moves upwards till the lower surface of Liver.
• From the liver it turns to the left.
• The turn is called “Right Colic Flexure (Hepatic Flexure)”.

Transverse Colon:

• It starts from Hepatic Flexure and runs left toward Spleen.
• Just below the spleen it turns downwards.
• The turn is called “Left Colic Flexure (Splenic Flexure)”.

Descending Colon:

• At Splenic Flexure the colon turns and runs downwards till iliac crest.
• This part is called a descending colon.
• Descending colon ends at Sigmoid Colon.

Sigmoid Colon:

• It starts from descending colon and ends in rectum.

Rectum:

• Starts from sigmoid colon and ends in anal canal.
• 13 cm long.
• Storage site for fecal material before excretion.
• Contains rich blood supply.

Anal Canal:

• Last part of GIT that opens in an external environment.
• Around 4 cm in length.
• Mucous membrane is arranged in folds called “Anal columns” it contains rich blood supply.
• Opening to an external environment is called “Anus”.
• Anus is guarded by two sphincters,
  • Internal Anal Sphincter.
  • External Anal Sphincter.
• Internal anal sphincter is made up of smooth muscles hence is involuntary in nature.
• External anal sphincter is made up of skeletal muscles hence is voluntary in nature.
• These sphincters allow defecation of feces.

Functions of Large Intestine:

1. Absorption:
   1. Large intestine mainly deals with absorption of water.
   2. It also absorbs many minerals, certain vitamins and alkaline drugs.
2. Microbial Flora:
   1. Large intestine provides a friendly environment for growth of many microbes and hence is heavily colonized by many bacterias.
   2. These microbes are called “Normal Microbial Flora”.
   3. Normal microbial flora synthesizes certain vitamins like folic acid, cyanocobalamin etc.
   4. The microbial flora also prevents infections from pathogenic microbes found in food.
   5. The microbes when they enter other parts of the body may cause infection e.g. E. coli.
3. Defecation:
   1. The “mass peristalsis” movement rises in sigmoid colon and pushes fecal material into rectum.
   2. Stretched rectum produces an urge for defecation.
   3. Sphincters are opened and fecal material is expelled out.

Accessory Organs:

• An organ that helps with digestion but is not part of the digestive tract. 
• The accessory digestive organs are the tongue, salivary glands, pancreas, liver, and gallbladder.

Salivary Glands:





• These exocrine glands secrete a secretion called saliva in the oral cavity.
• There are 3 pairs of the salivary glands,
  • Parotid Glands.
  • Submandibular glands.
  • Sublingual glands.
• Parotid glands:
  • Largest salivary glands.
  • Present below the ears.
  • Secrete saliva in oral cavity through parotid ducts.
  • Saliva contains large amounts of Salivary amylase.
  • More fluidity in nature.
• Submandibular Glands:
  • Present below the mandible.
  • Secrete saliva in oral cavity through submandibular ducts.
• Sublingual Glands:
  • Smallest salivary glands.
  • Present below the tongue.
  • Saliva contains less amount of salivary amylase.
  • Thick in nature.
• Saliva:
  • Secretion of salivary glands is called “Saliva”.
  • It is colorless.
  • It is 99.5% water and remaining .5% is inorganic salts, enzymes and waste materials like urea, uric acid etc.
  • Saliva has a slight acidic pH 6.35 to 6.85.
  • Saliva contains an enzyme “Salivary amylase (Ptyline)”.
  • Daily secretion is 1 to 1.5L.
• Functions:
  • Lubrication of the mouth.
  • Lubrication and moistening of food.
  • Continuous flushing and cleaning of oral cavity helps checking microbial growth.
  • Many drugs and waste materials are excreted via saliva.
  • Salivary amylase causes chemical digestion of starch.

Liver:





• Largest gland in the body.
• Located on the left side below lungs in the upper abdominal cavity.
• Superficially it is covered by peritoneum which separates it into lobes.
• Has two main lobes – right and left lobe.
• Right lobe is further divided into caudate, and quadrate lobe.
• The hepatic blood vessels enter the liver at the porta hepatis.
• The gallbladder rests in a recess on the inferior surface of the right lobe.
• The structural and functional unit of liver is “Lobule”.
• Each liver lobule is hexagonal in shape.
• Composed of hepatocyte (liver cell) plates radiating outward from a central vein,
• Portal triads are found at each of the six corners of each liver lobule.
• Liver sinusoids – enlarged, leaky capillaries located between hepatic plates
• Kupffer cells – hepatic macrophages found in liver sinusoids.
• Functions of Hepatocytes:
  • 
    Production of bile
  • Processing bloodborne nutrients
  • Storage of fat-soluble vitamins
  • Detoxification.
• 
  Secreted bile flows between hepatocytes toward the bile ducts in the portal triads and is stored in Gallbladder.
• Composition of Bile:
• A yellow-green, alkaline solution containing bile salts, bile pigments, cholesterol, neutral fats, phospholipids, and electrolytes
• Bile salts are cholesterol derivatives that:
• Emulsify fat
• Facilitate fat and cholesterol absorption
• Help solubilize cholesterol
• Enterohepatic circulation recycles bile salts
• The chief bile pigment is bilirubin, a waste product of heme.

Functions of Liver:

1. Metabolism:
   1. Carbohydrate Metabolism: 
      1. Stores Glycogen.
      2. Gluconeogenesis.
      3. Glycogenolysis.
   2. Fat Metabolism:
      1. Oxidation of fatty acids. (Liver utilizes energy through fat metabolism).
      2. Synthesis of Lipoproteins.
      3. Synthesis of phospholipids and cholesterol.
      4. Converts large amounts of carbohydrates and proteins into fats.
   3. Protein Metabolism:
      1. Parenchymal cells of the liver synthesize plasma proteins.
      2. Deamination of amino acids.
      3. Urea cycle to remove ammonia from the body.

2) Secretion of bile.

3) Storage of many vitamins like fat soluble vitamins and cyanocobalamin.

4) Breakdown of RBCs and defense against microbes by Kuffer cells.

5) Production of heat.

6) Detoxification of drugs and bacterial toxins.

Gallbladder: 





• It is a thin walled green muscular bag present on the ventral surface of the liver.
• 8-10 cm long.
• Stores and concentrates bile by absorbing its water and ions.
• Releases bile via “Cystic Duct” which is connected to “Bile Duct”.
• When acidic chyme enters duodenum the “I” cells of small intestine secrete “Cholecystokinin” which stimulate liver for bile production.
• Cholecystokinin also causes contraction of the gallbladder releasing bile in duodenum.
• Anatomically gallbladder is divided into Fundus, body and neck.
• Common diseases of gallbladder include gallstone (Crystallization of cholesterol”, obstructive jaundice.

Pancreas:





• It is a soft oblong organ present below the stomach.
• It is attached to duodenum and ends near spleen.
• It has mixed exocrine and endocrine functions.
• The pancreas has a head, a body, and a tail. 
• It delivers pancreatic juice to the duodenum through the pancreatic duct.
• The exocrine part of the pancreas arises as little grape-like cell clusters, each called an acinus (plural = acini), located at the ends of pancreatic ducts.
• The acini secrete pancreatic juice which contains a large amount of pancreatic enzymes.
• The pancreatic duct along with bile duct opens in duodenum in an area called as “Hepatopancreatic ampulla”, this part is guarded by a sphincter called “hepatopancreatic sphincter” which controls entry of bile and pancreatic juices in duodenum.
• Islets of Langerhans (EndocrineCells) represents a group of cells that appear surrounded by acini (Exocrine Cells).
• Islets of Langerhans contain three types of cells with endocrine function.
  • Ɑ (Alpha Cells): Secrete “Glucagon” 
  • 𝛃 (Beta Cells): Secrete “Insulin”.
  • 𝞭 (Delta Cells): Secrete “Somatostatin”.
  • Islets of langerhans cells also secrete a local hormone called “Pancreatic Polypeptide”.
• Pancreatic Juice:
  • It's a clear secretion secreted by Pancreas in duodenum.
  • Pancreas secretes around one liter of pancreatic juice everyday.
  • It contains mainly water, some salts, sodium bicarbonate and several digestive enzymes.
  • The proteolytic enzymes are secreted in inactive forms which get activated in the duodenum, while amylases, lipases and others are secreted in active forms.
  • Pancreatic secretion is controlled by “secretine” a local hormone produced by “S” cells of small intestine.
• Hormones of Pancreas:
  • Endocrine part of pancreas is Islets of Langerhans.
  • Beta cells of Islets of Langerhans secrete “Insulin” which is responsible for conversion of glucose to glycogen and also for entry of glucose in the cells, hence maintaining the blood sugar levels.
  • Absence or deficient insulin secretion gives rise to a condition called as “Diabetes mellitus”.
  • Alpha cells of Islets of Langerhans secrete a hormone called “Glucagon” responsible for conversion of glycogen to glucose, hence providing sugar to the body in fasting conditions.
  • Delta cells of Islets of Langerhans secretes “Somatostatin” its a local hormone and inhibits secretion of other hormones like “Gastrin, Secretin, Insulin, Glucagon etc.”