HUMAN DIGESTIVE SYSTEM
Human digestive system parts and functions The DIGESTIVE SYSTEM is involved in the process of digestion. This digestion process takes place in ALIMENTARY CANAL.
Human digestive system parts and functions
ALIMENTARY CANAL:-
The Alimentary canal starts from mouth and extends through stomach and ends with large intestines.We can study them through each part.
I. HISTORY OF GUT WALL:- This have 4 layers namely;
- Serosa
- Muscularies
- sub-mucosa
- Mucosa
II. MOUTH:- The mouth leads to the oral cavity or buccal cavity.The mouth and it's parts can be studied in detailed;
- Palate
- Tooth
- Tongue
- Papillae
|
STRUCTURE OF HUMAN MOUTH |
A. PALATE:- It is used to chew and breath at same time. It hangs from free border of soft palate called uvula(little grape).
B. TOOTH:- Here the human teeth shows 3 main features:-
THECODONT, HETERODONT, DIPHYODONT.
- Thecodont means their teeth are embedded in the sockets of jaw bone.
- Heterodont means their teeth are of different shapes due to different functions. In human we see 4 types namely; Incisors,Canines,Pre-molars,Molars.
- Diphyodont means the teeth appears twice in their life time.First appeared teeth are called as milk teeth or Primary teeth.Second apperaed teeth are called as Permanent teeth or secondary teeth.
The teeth in human are lined by PERIODONTAL
MEMBERANE.
The structure of tooth shows 3 main regions:-
The tooth is made up of bone like DENTINE,Which is made up of rich calcium, it is secreted by ODONTOBLAST of mesodermal origin and dentine covered by ENAMEL secreted by AMELEOBLAST of ectodermal origin.Dentine of root is covered by another bone like substance called CEMENTUM."Enamel'" is the "hardest substance" in our body. As we know, we have 2 sets of teeth in our life time:- Milk teeth and Permanent teeth.
- PRIMARY TEETH:- These are also known as milk teeth, these appear in kid stage. These are 20 in number.(2-Incisors,1-Canine,2-molars).These are replaced during 6 to 12 years of age.
The dental formula is:- 2102/2102.
- SECONDARY TEETH:- These are also known as permanent teeth, these are 32 in number.(2-Incisors,1-Canine,2-Pre molars,3-Molars). The third set of teeth appear at the age of 21,called as WISDOM TEETH.
The dental formula is:- 2123/2123.
The 4 types of teeth have 4 different functions;
- Incisors- (2) Chisel shaped,used in cutting of food.
- Canines- (1) Dagger shaped called cuspid,used for tearing.
- Pre molars- (2) Bicuspid,cheek teeth,used to crush and grind.
- Molars- (3) Cheek teeth,used to grind,third set of teeth called wisdom teeth appeared at 21 years.
C. TONGUE:- It is a freely movable muscular sense organ attached to floor of oral cavity by FRENULUM. It is inverted V-shaped, and furrow. At an angle of this furrow,there is a small pit called as FORAMEN CAECUM. Tongue is called as UNIVERSAL TOOTH BRUSH.
D. PAPILLAE:- Papillae are present on upper surface of tongue and some bears taste buds. The different types of papillae are;
- CIRCUMVALLATE PAPILLAE:- Large inverted V-shaped row,on posterior surface/back of the tongue.
- FUNFIFORM PAPILLAE:- Mushroom shaped anterior magin and on tip of the tongue.
- FILLIFORM PAPILLAE:- Present on either surface of tongue and pointed,thread like structures.
- FOLIATE PAPILLAE:- The foliate papillae are also there on lateral margins of the tongue near base.
Taste areas of tongue are;
- Sweet-Tip of the tongue.
- Salt-Tip and sides of the tongue.
- Sour-Sides and base of the tongue.
- Bitter-Base of the tongue.
STRUCTURE OF HUMAN TONGUE
III.PHARYNX:- Oral cavity leads to a funnel shaped tube called as pharynx. It serves as common passage for food and air.
A. NASOPHARYNX:- Upper part of the pharynx,made up of lymphoid tissue. Adenoid/pharyngeal tonsils are present on roof of pharynx,paired lingual tonsil located at the base of the tongue.
B. OROPHARYNX:- Middle part of the pharynx,oral cavity opens into it,an ovoid palatine tonsil lies on either sides of the oropharynx.
C. LARYNGOPHARYNX:- Lower part of the pharynx,leads into esophagus and into voice box/larynx, and it have EPIGLOTTIES.
PHARYNX OF HUMAN
IV. ESOPHAGUS:- It is called as Food tube, it is a thin,long muscular, posterior to trachea, lined by non-keratinized stratified squamous epithelium. An involuntary sphincter of smooth muscles called as Cardiac sphincter/lower esophageal sphincter, which regulates opening of esophagus into stomach.STRUCTURE OF ESOPHAGUS
V. STOMACH:- It is v-shaped distensible, muscular bag in upper left portion of abdominal cavity, inferior to diaphragm, it is used in MIXING AND HOLDING. Stomach have 3 portions;
- CARDIAC PORTION:- Cardiac sphincter is present through which esophagus opens into it.
- FUNDIC REGION:- Food from cardiac portion enters to fundic region, from here it moves on to pyloric portion.
- PYLORIC PORTION:- Pyloric aperture is guarded by pyloric sphincter through which it opens into duodenum.
Entry of food into stomach is guarded by GASTRO-ESOPHAGAL SPHINCTER. When stomach is empty,mucosa lies in large irregular folds called RUGAE, which look like whrinkles.
STRUCTURE OF HUMAN STOMACH
VI. SMALL INTESTINES:- Long, 3m in length and averages 2.5cm in diameter. Starts at pyloric sphincter of stomach, coils and opens into large intestines, it shows 3 regions.
A. DUODENUM:- Short, 0.3m, U-shaped, opening of stomach into it guarded by pyloric sphincter, it receives chyme from stomach and digestive secretions from pancreas and liver.
B. JEJUNUM:- Long 1m, middle part, the bulk of chemical digestion and nutrient absorption occurs in it.
C. ILLEUM:- Longest 2m highly coiled, joins the large intestine, the opening from illeum into large intestine is guarded by ileocaecal value.
Villi:- Villi are tufts of hairs/finger like projections of mucosa of small intestine. Each villi covered by epithelium and supplied with an arteriole, a venule, a blood capillary called LACTEAL. Villi have plasma membrane and produce no.of microvilli.
STRUCTURE OF HUMAN SMALL INTESTINE
VI. LARGE INTESTINES:- It is 1.5m long, 6.5cm in diameter. Plays a main role in completion of absorption, production of vitamins, formation of faeces, expulsion of faeces. This shows 4 regions.
A. CAECUM:- Small blind sac, it hosts some symbiotic micro-organisms. A narrow finger-link tubular projection with lymphoid tissue called vermiform appendix arises from caecum. It have a vestigial organ. APPENDICITIS is inflammation of appendix and it need APPENDECTOMY which is a surgical removal of appendix within 24 hrs. The caecum opens into colon.
B. COLON:- Colon is a food passage and it shows 4 parts;
- ASCENDING COLON
- DESCENDING COLON
- TRANSVERSE COLON
- SIGMOID COLON
Longitudinal muscles of muscularis of large intestine are thickened and form conspicuous bands called TAENIAE COLI. (Taeniae- flat bodies.) Tonic contractions of bands gather colon into a series of pouches called as HAUSTRA.
C. RECTUM:- It is 20cm long, straight muscular tube and expandable organ for temporary storage of faeces.
D. ANAL CANAL:- It is the terminal portion of rectum called as anal canal. It opens to exterior by anus guarded by an internal anal sphincter of smooth muscle which is involuntary. An external anal sphincter of skeletal muscle is voluntary in function.
STRUCTURE OF HUMAN LARGE INTESTINE
These are the main Human digestive system parts and functions which are used in the process of digestion of food in human.
Very nice blog, clearly understanding!!!
ReplyDeleteTnq so much
DeleteHearty congratulations dear...
ReplyDeleteKeep rocking ๐๐
Tnq aunt๐๐ฅฐ
DeleteVery nice Prasanna supriya..!!
ReplyDeleteTnq so much yar
DeleteSuper very good janu
ReplyDeleteTnq aunty๐ค
DeleteWowwwww... Congrats...Keep going. All the best ๐ God Bless You ๐
ReplyDeleteTnq aunty๐ค
Delete