Digestive System Components

Module 10 - The Digestive System

Section 01 - Components of the Digestive System

• The digestive tract includes the mouth, oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, and anus.
• The accessory digestive organs include the tongue, teeth, salivary glands, liver, biliary ducts and gallbladder, and pancreas.
• Digestion involves the mastication of food in the mouth into smaller pieces, facilitating enzymatic breakdown into smaller molecules.
• Absorption occurs mainly in the small intestine, where nutrients, water, and vitamins are absorbed, with some absorption in the large intestine.
• Secretion occurs in the stomach, where cells in the mucosal wall release gastric acid for chemical digestion.
• Motility involves muscle contractions in the esophageal wall to move food down to the stomach.
• Elimination of waste occurs through the process of defecation, where unabsorbed materials are removed.
• The mucosa is the innermost layer of the digestive tract wall and includes the surface epithelium, lamina propria, and muscularis mucosae.
• The surface epithelium reflects the organ's function, such as secretion, absorption, or protection.
• The lamina propria is a layer of loose connective tissue under the surface epithelium.
• The muscularis mucosae is a layer of smooth muscle fibers under the lamina propria.
• The submucosa is a layer composed of dense irregular connective tissue containing blood vessels, lymphatics, glands, and nerve plexuses.
• The muscularis externa consists of circular and longitudinal layers of smooth muscle with nerve plexuses, responsible for muscular contractions.
• The serosa/adventitia is the outermost layer.
• A serosa is present when the outer layer is a serous membrane.
• An adventitia is present when the outer layer is made of loose connective tissue.

Section 02 - Oral Cavity

• The vestibule is the space between the cheeks, lips, gums, and teeth.
• The oral cavity proper includes all areas of the mouth other than the vestibule.
• The palate forms the superior border of the oral cavity and is divided into the hard palate (bone) and soft palate (muscle).
• The uvula is the posterior extension of the soft palate.
• Teeth are important for the mechanical digestion of food, and humans have two sets: deciduous (“baby teeth”) and permanent teeth.
• Deciduous teeth consist of 2 incisors, 1 canine, and 2 molars in each quadrant.
• Permanent teeth consist of 2 incisors, 1 canine, 2 premolars, and 3 molars in each quadrant.
• The tongue is a muscle associated with speech, taste, and mechanical manipulation of food.
• Intrinsic muscles control the shape of the tongue.
• Extrinsic muscles control the tongue's movement.
• The frenulum anchors the tongue to the floor of the mouth.
• The superior and lateral surfaces of the tongue are covered in papillae.
• Papillae are bumps that contain taste buds.
• The pharynx is a part of both the digestive and respiratory systems.
• Salivary glands secrete digestive enzymes and mucus to aid in chewing and breaking down food.
• Parotid glands secrete serous fluid and are located anterior and inferior to the external ear opening.
• Submandibular glands secrete serous and mucous fluid and are inferior to the mandible.
• Sublingual glands secrete mucus and are inferior to the tongue.
• Tonsils, collections of lymphoid tissue in areas of the pharynx, play a role in the immune system; palatine, pharyngeal, and lingual.

Section 03 - Esophagus and Stomach

• The esophagus is a muscular tube ~25 cm long, extending from the pharynx to the stomach.
• The mucosa of the esophagus is a stratified squamous epithelium to protect from friction.
• The submucosa of the esophagus contains mucus-secreting glands for lubrication.
• The muscularis externa of the esophagus consists of smooth muscle and skeletal muscle.
• In the upper ⅓ of the Esophagus it consists of skeletal muscle only, in the middle ⅓ is a mix of both and in the lower ⅓ it consists of smooth muscle only.
• Most of the Serosa/Adventitia layer of the Esophagus is made of loose connective tissue Adventitia.
• The stomach is a J-shaped organ divided into the fundus, body, and antrum.
• The antrum connects to the small intestine.
• The shape of the stomach gives rise to the lesser and greater curvatures.
• The greater omentum is an apronlike structure that hangs off the greater curvature, covering and protecting abdominal viscera.
• The mucosa of the stomach is folded into ridges called rugae.
• Made up of the simple columnar epithelium, which protects the stomach from acidic conditions.
• Inward folds extend into the lamina propria to form gastric glands.
• Contain and secrete stomach acids for chemical digestion.
• The submucosa contains blood vessels, lymphatics, glands, and nerve plexuses.
• The muscularis externa has three layers of smooth muscle arranged in different directions - longitudinal, circular, and oblique.
• The serosa/adventitia is covered by serosa.

Section 04 - The Intestines

• The small intestine attaches to the posterior abdominal wall, approximately 6 meters long, and is divided into three parts: duodenum, jejunum, and ileum.
• The duodenum is a 25 cm C-shaped structure enclosing the head of the pancreas.
• The jejunum is 2.5 meters in length, mostly in the upper left quadrant of the abdomen.
• The ileum is 3.5 meters in length, mostly in the right lower quadrant of the abdomen.
• Villi are finger-like projections that extend into the lumen.
• Epithelium contains simple columnar cells and absorbative cells with microvilli to increase surface area.
• Lamina propria forms the core of each villus and contains blood and lymphatic capillaries.
• Intestinal glands, also known as crypts of Lieberkühn, are deep folds of mucosa that secrete intestinal juices.
• Plicae circulares, or circular folds formed from the mucosa and submucosa, increase the surface area for absorption.
• Submucosa, duodenal (Brunner's) glands secrete alkaline mucus to protect from stomach acid.
• The muscularis externa contains smooth muscle organized into circular (inner) and longitudinal (outer) layers.
• Outermost Serosa layer.
• The large intestine is the terminal portion of the digestive tract.
• The cecum is the first portion and has a vermiform appendix.
• The colon is divided into four sections (ascending, transverse, descending, and sigmoid).
• Transverse colon extends from below the liver, crossing the abdomen to join the descending colon just below the spleen.
• Sigmoid colon is the S-shaped terminal portion that leads to the rectum.
• Rectum extends from the sigmoid colon to the anal canal.
• The mucosa, which lacks villi or plicae circulares, has a simple columnar epithelium containing goblet cells.
• Contains intestinal glands and accumulations of lymphatic tissues are present in the lamina proper.
• Submucosa contains blood vessels, lymphatics, glands, and nerve plexuses.
• Depending on the location, the muscularis externa has a unique arrangement.
• In the cecum and colon, the outer longitudinal layer forms three longitudinal bands that forms sac-like structures called haustra.
• In the rectum the three teniae coll merge to form the continuous longitudinal muscular layer.
• The anal canal circular muscle layer into the internal anal sphincter, used in waste excretion.
• The serosa/adventitia layer can be covered in either serosa or adventitia.
• The anal canal is the last portion of the digestive tract.
• The anal column are longitudinal ridges in the canal.
• External and internal anal sphincters are used to maintain continence and relax to enable evacuation.

Module 11 - The Accessory Digestive Organs and Urinary System

Section 01 - Accessory Digestive Organs

• The liver performs many functions in the digestive system, including bile production for fat digestion and storing glucose as glycogen.
• Aids in the metabolism of toxins, drugs, and alcohol in the blood.
• It is located in the upper right abdominal quadrant, under the diaphragm, and anterior to the inferior vena cava.
• The liver includes right, left, caudate, and quadrate lobes.
• Ligaments attach the liver to the abdominal peritoneum and diaphragm; The falciform ligament separates the left and right lobes.
• Coronary ligaments suspend the liver from the diaphragm.
• The porta hepatis (hilum) is where the hepatic vessels and ducts enter and leave the liver and is located on the underside of the liver.
• The common hepatic duct drains bile produced by the liver; it joins with the gallbladder’s cystic duct to form the common bile duct.
• The portal vein carries nutrient-rich blood from the digestive system to the liver.
• The hepatic artery carries oxygenated blood to the liver.
• Hepatocytes or liver cells, arrange in portal triads in hexagonal lobules, which make up the functional units of the liver.
• Plates or cords, which radiate outward from the central vein.
• Sinusoids, spaces between the plates in which venous blood flows.
• Portal (hepatic) triads contain branches of the hepatic artery, portal vein, and common hepatic duct.
• Each lobule is surrounded by 6, one at each corner of the hexagon.
• Nutrient-rich blood in portal veins enters the sinusoids where nutrients are absorbed into hepatocytes.
• Blood drains into a central vein which join making hepatic veins, with a path leading to the inferior vena cava.
• Hepatocytes produce bile into small channels of canaliculi that empty into bile ducts of the portal triad and form the common hepatic duct.
• In cirrhosis, presence of scar causes issues functioning properly as tissues become fibrosis and fatty, blocking blood and bile flow, causing jaundice and a distended abdomen.
• The gallbladder is a muscular sac that stores and concentrates bile, with the fundus, body and neck region.
• The biliary system includes ducts that connect the liver and gallbladder; hepatic ducts from the liver drain bile into the common hepatic duct.
• The cystic duct attaches to the common hepatic duct and transports bile to and from the gallbladder.
• The common bile duct is where the hepatic and cystic ducts meet, draining bile into the duodenum.
• The pancreas is a mixed gland with exocrine (enzyme secretion) and endocrine functions and lies deep to the stomach.
• The head is at the duodenum's concavity.
• The body extends toward the spleen.
• The main pancreatic duct collects exocrine products, fusing with the common bile duct at the hepatopancreatic ampulla of Vater to empty into the duodenum.
• Pancreatic acini secrete enzymes into the duodenum.
• High in digestive enzymes and bicarbonates for the aid of acidity.

Section 02 - Kidneys

• The kidneys initiate the urinary system, filtering blood and producing erythropoietin.
• They are bean-shaped organs located on either side of the spine against the posterior abdominal wall.
• Typically fist sized.
• Lie level on the right due to the liver.
• The hilum is the medial concave side, for renal and nerve passage ways.
• It’s continuous with internal space in each kidney, which is filled with the renal sinus of fatty tissues.
• Supportive tissues surround the kidneys, offering protection and cushion; the renal capsule covers the outter surface protects injury and pathogens.
• Adipose capsule offers cushion and protection to tissue with by surrounding tissues.
• The kidney divides separate regions into cortex and medulla.
• Cortex is outer layer and medulla is deep to cortex
• The renal pyramids exist in the medulla
• Apex of these pyramids are called renal papilla
• Based on the kidneys are divided into renal lobes.
• Recieve blood from renal arteries and drain into renal veins
• Nephron's blood is composed of two renal capsuled
• filtration happens when components of blood move from capillaries to Bowmans pace.
• Collecting ducts travels into tubules and collects in the medulla
• Once fluid leaves it becomes urine
• Juxtaglomerular apparatus regulates pressure by monitoring ion concentrations in filtrate.
• Juxtaglomerular are smooth muscle.
• The long the tubes, that connect with musclar tubes.
• Start at renal pelvis and go though urethra
• Composed of muscle lining for muscle action.

module 12 - The Reproduction System

Section 01 - The Male Reproduction System

• The testes is the site where sperm creation and development occurs and is protected by tissues
• Two oval shapes which have 4-5cm in length and 2.5-3cm in diameter
• Tunica vaginalis is outer protective covering.
• Extentions create compartments in lobules, which create testicular cord.
• Seminferous Tubules is a lightly caed tubules that function for sperm production,
• Each create 600-1000 and can be 80cm long when ucoiled.
• Leydig cells produce secretion in testrone.
• Male sperm carries gentitic information.
• Head with nulceus and are somal cap, that halps connect to the egg
• Neak connect head to midpiece
• Midpiece helps produce energy.
• Has source of movement.
• Scrotum is derives from abdomial wall and can be reposistioned.
• It contains skin and fascia.
• Has two muscles and helps to control temperature.
• Dartos muscle located superficially and helps controll the sking
• Helps change temp by altering surface temps.
• Cremaster, reflexively contracts and draws testes to the body wall.
• Epididymis is first portion which are shaped like comas.
• Contains, receives sperm, the head and the body which it lies on.
• Vas defrens storgagesaand transits sperm from the epididimus to the urethra.
• It helps sperm through the vas deferens
• Contains ejeculatory that is joined by and the seminal vesicles
• Part of uniary and transports sperm out the body.

Accessory Gland

• Seminal values create fluid and nutrients through ejaculation.
• Prostate gland creates fluid through enzymes and sugars.
• It consists tubular area and in smooth muscle an inCT.
• Bolubrehal two create clear substance and produce thick like surface
• It secrates traces for production rate.
• Penius has the uriary, and helps help carry in both pathwa\ys through urine and sperm
• Pevis is a ributed fix with Attaches of to ischiuem in the pelvic bones It consist of three cylinders of issues an urine. Body is the main portion with cyliders Pennis has expansion. Corpora Cavertsa most mass of the pevies. Attachtothe pony pelvis and muscles Speniglosum to fyll with glands Proxaion is enlargetan bulb

The Section 02- The Female Reproductive System

• Overy paired location nears side of pelvis

• Eges and store where and producd

• Ovais is procted that supports overie

• Is also to protect overie.

• Is surrouded bu conetcice lise and capule of algubina

• Deep oveires and madulla.

• Cortex overires

• Conatin many folicies.

• Folicle os the modt in a cell layer

• Layers with cel.

• Secry folicaly with fluid and it

• Terirary is a follicle.

• Antrum. From remains and more progestions. Dose to extent.

If tilization doesnt occure Duse in de genterate

• MEdula overs is the line.

• Fallopain is the feval reproductive system

• Open inte cavittit.

• Progetors cature

• Fumbrie capture the egg

• And Ampila widdit

• Istmuos is closedto the opening

• Sape which orga in locaitons and carrites. Cervix

• Contains cersible

• Internal conextes

• Externam conetd tex It consist three layerss Engodmedri is the changes to cylcers.

• Middle. Outer