The Digestive System

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Questions and Answers

What is the main function of the Von Ebner Glands?

To produce taste buds

To facilitate taste sensation and washing away food particles (correct)

To detect diseases through tongue color

To mix food during mastication

Which type of lingual papillae is most common and has no taste buds?

Vallate or Circumvallate Papillae

Foliate Papillae

Filiform Papillae (correct)

Fungiform Papillae

What is the surface of the tongue that contains lingual papillae?

Dorsal Surface (correct)

Rough surface

Ventral Surface

Smooth surface

What is the function of the tongue during mastication and swallowing?

To help speak and mix food during mastication and swallowing Signup and view all the answers

What is the characteristic of the epithelium on the ventral surface of the tongue?

Non-keratinized stratified squamous epithelium Signup and view all the answers

What type of corticoids are mainly secreted by the Zona Fasiculata?

Glucocorticoids and some aldosterone Signup and view all the answers

What is the main function of the cells in the Zona Reticularis?

Producing androgens Signup and view all the answers

What is the characteristic of chromaffin cells in the adrenal medulla?

They have lost their axons and dendrites Signup and view all the answers

What is the function of the pineal gland?

Regulating the body's circadian rhythms Signup and view all the answers

What is secreted by pinealocytes during the day?

Serotonin Signup and view all the answers

What is the main function of myelin sheaths in nerve fibers?

To increase nerve impulse conduction through salutatory conduction Signup and view all the answers

What type of neuroglial cells are found in the PNS?

Schwann and satellite cells Signup and view all the answers

What is the main function of ganglia?

To provide a site for the cell bodies of neurons and glial cells Signup and view all the answers

What type of neurons are found in Autonomic ganglia?

Multipolar neurons Signup and view all the answers

What is the function of the Endoneurium?

To surround individual nerve fibers Signup and view all the answers

What is the primary function of Pneumocyte type II cells?

To secrete surfactant to decrease surface tension of the alveoli Signup and view all the answers

What is the characteristic of the epithelium in the bronchioles?

Lined with pseudostratified ciliated columnar cells Signup and view all the answers

What is the effect of asthma on the bronchioles?

Constriction of smooth muscle in bronchioles, causing a decrease in their diameter Signup and view all the answers

What is the result of hyaline membrane disease?

Labored breathing due to a lack of pulmonary surfactant Signup and view all the answers

What is the result of emphysema?

Destruction of alveolar walls and formation of large cyst-like sacs Signup and view all the answers

What is the main function of the ear pinna?

To direct sound waves to the inside Signup and view all the answers

What is the characteristic of the epithelium on the cornea?

Stratified squamous non-keratinized epithelium Signup and view all the answers

What is the function of the choroid?

To nourish the outer part of the retina Signup and view all the answers

What is the characteristic of the ciliary body?

It is formed of two layers of cells, inner and outer Signup and view all the answers

What is the amount of melanin in the iris pigmented epithelium responsible for?

Determining eye color Signup and view all the answers

What is the primary function of the Malpighian Renal corpuscles?

To form the glomerular filtrate by the process of dialysis Signup and view all the answers

Which of the following layers of Bowman's capsule is formed of modified simple squamous cells known as podocytes?

Visceral layer Signup and view all the answers

What is the main function of Mesangial cells?

To act as structural support to podocytes and vessels Signup and view all the answers

What is the main difference between the proximal convoluted tubules and the distal convoluted tubules?

The proximal convoluted tubules have more apical microvilli Signup and view all the answers

What is the location of the Juxtaglomerular Complex?

Between the afferent and efferent arterioles Signup and view all the answers

What type of epithelium lines the vagina?

Stratified squamous non-keratinizing epithelium Signup and view all the answers

What is the function of the stereocilia in the epididymis?

Increase the apical surface area for absorption Signup and view all the answers

What type of epithelium lines the ejaculatory duct?

Folded simple columnar epithelium Signup and view all the answers

What is the characteristic of the epithelium covering the penis?

Keratinized stratified squamous epithelium Signup and view all the answers

What is the function of the smooth muscles in the vas deferens?

Peristaltic contraction for ejaculation Signup and view all the answers

Study Notes

Digestive System

The digestive system includes the gastrointestinal tract (alimentary canal)
The digestive system consists of the oral cavity, digestive tract, and digestive glands

Oral Cavity

The oral cavity includes the lips, tongue, palate, and cheeks
The lips consist of 3 histological regions:
- Outer surface: thin hairy skin with hair follicles, sebaceous, and sweat glands
- Inner surface: mucous membrane with labial muco-serous glands that produce saliva
- Red margin (vermillion): partially keratinized stratified squamous epithelium

Tongue

The tongue has 2 surfaces:
- Dorsal surface (rough): covered by partially keratinized stratified squamous epithelium with lingual papillae
- Ventral surface (smooth): covered by non-keratinized stratified squamous epithelium
The tongue has 4 types of lingual papillae:
- Filiform papillae: most common, conical in shape, and have no taste buds
- Fungiform papillae: few in number, reddish in color, and have few taste buds
- Foliate papillae: present on each side of the tongue
- Vallate or circumvallate papillae: 8-12 in number, present in a V-shaped groove, and rich in taste buds

Esophagus

The esophagus is a 25-cm long muscular tube that connects the oral cavity to the stomach
The esophagus wall consists of 4 layers:
- Mucosa: non-keratinizing stratified squamous epithelium, lamina propria, and mucous glands
- Submucosa: contains mucous glands (esophageal glands)
- Musculosa: skeletal in upper 1/3, mixed in middle 1/3, and smooth in lower 1/3
- Adventitia: connective tissue covering with blood vessels and lymphatic vessels

Stomach

The stomach is a sac-like muscular structure extended for digestion
The stomach is the first station for digestion
The stomach can be used to detect some diseases:
- Pale red color: may indicate anemia
- Blue color: lack of oxygen in the blood leading to increase carbon dioxide and cyanosis
- Red color: indicates healthy

Taste Buds

Taste buds are present on the tongue and contain 3 layers
Each taste bud has:
- Receptor taste cells (sensory nerve-like microvilli for absorption)
- Supporting cells (act as bodyguards)
- Basal cells (act as stem cells for renewal of other 2 cells)

Pituitary Gland

Consists of two glands: neurohypophysis and adenohypophysis
Adenohypophysis has three parts: pars distalis, pars intermedia, and pars tuberalis
Pars distalis has two types of cells: chromophils (acidophils and basophils) and chromophobes

Chromophils

Acidophils (35%): have acidophilic granules in cytoplasm, produce growth hormone and prolactin
Basophils (15%): have basophilic granules in cytoplasm, produce TSH, ACTH, MSH, FSH, LH, and ICSH

Chromophobes

Poorly stained, make up 50% of cells, function as reserve or stem cells

Pars Nervosa

Consists of unmyelinated nerve fibers, Herring bodies, fenestrated blood capillaries, and pituicytes
Function: stores and releases oxytocin, involved in sexual reproduction

Thyroid Gland

Has two lobes connected by a narrow isthmus
Stroma consists of capsule, C.T septa, and reticular C.T
Parenchyma consists of secretory cells, producing T3 and T4 hormones

Thyroid Hormone Production

Follicular cells secrete T3 and T4 hormones
Parafollicular cells (C cells) secrete calcitonin hormone, which decreases bone osteoclast activity and lowers blood calcium levels

Thyroid Disorders

Thyrotoxicosis: increased follicular cells and thyroxine secretion
Iodine deficiency goiter: hypothyroidism due to low iodine in diet
Myxedema: hypothyroidism leading to fatigue, sleeping, muscular and mental sluggishness
Graves' disease: autoimmune disease, exophthalmic goiter, and hyperthyroidism

Parathyroid Glands

Four small glands, behind the thyroid gland
Stroma consists of capsule, septa, and reticular C.T
Parenchyma consists of chief cells (secrete parathyroid hormone) and oxyphil cells

Adrenal Glands

Two glands, one above each kidney, formed of peripheral cortex and central medulla
Stroma consists of capsule, septa, and reticular C.T
Parenchyma consists of adrenal cortex and adrenal medulla

Adrenal Cortex

Divided into three zones: zona glomerulosa, zona fasiculata, and zona reticularis
Zona glomerulosa: secretes mineral corticoids, mainly aldosterone
Zona fasiculata: secretes glucocorticoids, mainly cortisone and some aldosterone
Zona reticularis: secretes androgens, produces all hormones in the ovary after menopause

Adrenal Medulla

Consists of chromaffin cells and autonomic ganglion cells
Chromaffin cells: modified sympathetic ganglia cells, secrete epinephrine (80%) or norepinephrine (20%)
Autonomic ganglion cells: scattered between chromaffin cells, innervated by preganglionic sympathetic neurons

Pineal Gland

Also known as the third eye, affected by light
Stroma consists of capsule, septa, and reticular C.T
Parenchyma consists of pinealocytes, secretes melatonin (at night) and serotonin (precursor of melatonin during the day)

Nervous Tissue

The nervous system is divided anatomically into:
- Central Nervous System (CNS): Brain and spinal cord
- Peripheral Nervous System (PNS): Cranial, spinal nerves, and ganglia
There are approximately 10 billion neurons in the nervous system

Neurons

Neurons are the main cells of the nervous tissue, with stellate shape and long processes
Neurons have three parts:
- Dendrites: multiple elongated processes that receive impulses
- Soma or cell body: contains single central active nucleus, basophilic cytoplasm, and neurofilaments
- Axon: single elongated process that transmits nerve impulses
Classification of neurons according to their processes:
- Pseudounipolar: contains a common stem that divides into two branches (central and peripheral)
- Bipolar: contains two processes, an axon and a dendrite
- Multipolar: contains more than two processes

Classification of Neurons by Cell Body Shape

Pyramidal: pyramidal cells in cerebral cortex
Pyriform: purkinje cells of cerebellum
Stellate: AHCs of spinal cord and autonomic ganglia cells

Classification of Neurons by Function

Sensory neurons: receive stimuli from the environment and conduct them to CNS
Motor neurons: originate in CNS and conduct impulses to effector organs (muscle and glands)
Associated neurons (interneurons): connect sensory with motor neurons

Nerve Fibers

Made up of the axons of neurons
Most axons are enveloped by myelin sheaths, formed by oligodendrocytes in CNS and Schwann cells in PNS
Myelin sheath increases nerve impulse conduction through saltatory conduction
Connective tissue coats (sheaths) surround nerve fibers:
- Epineurium: surrounds the nerve trunk
- Perineurium: surrounds nerve bundles
- Endoneurium: surrounds individual nerve fibers

Neuroglial Cells (Nerve Glue)

Support and protect neurons
Divided into:
- Neuroglia of PNS: Schwann cells and satellite cells
- Neuroglia of CNS: Astrocytes, Oligodendroglia, Microglia, and Ependymal cells

Ganglia

Ovoid structures containing neuronal cell bodies and glial cells (satellite cells) supported by connective tissue
Types of ganglia:
- Sensory (Spinal) Ganglia: receive peripheral afferent impulses that go to the CNS
- Autonomic ganglia: receive efferent impulses to the effector organs (motor)

Respiratory System

Nasopharynx connects the nose and mouth to the trachea and is lined by respiratory epithelium (pseudostratified ciliated with goblet cells)
Oropharynx is continuous with the nasopharynx at the level of the soft palate

Larynx

Connects the pharynx to the trachea and is supported by hyaline cartilage and striated muscle
Vocal cords consist of skeletal muscle (vocalis muscle)
Anterior glottis is covered with stratified squamous epithelium, while the posterior glottis is covered with pseudostratified ciliated epithelium

Epiglottis

Prevents food from entering the respiratory system
Made of elastic cartilage and closes off the trachea to prevent inhalation of solids or liquids

Trachea

Mucosa is lined with respiratory epithelium (pseudostratified ciliated columnar epithelium with goblet cells)
Submucosa contains many seromucous glands
Hyaline cartilage is present in the trachea
Adventitia contains dense connective tissue

Bronchus and Bronchiole

Bronchus has a longer lumen and is lined with pseudostratified ciliated columnar epithelium
Bronchiole has a shorter lumen and is lined with ciliated columnar cells and Clara cells
Present plate of cartilage and mucoserous glands in bronchus, but not in bronchiole

Alveoli

Pneumocyte type I represents 97% of alveolar wall cells and forms part of the blood gas barrier
Pneumocyte type II represents 3% of alveolar wall cells and secretes surfactant to decrease surface tension of alveoli

Respiratory Diseases

Hyaline membrane disease occurs in those who lack adequate pulmonary surfactant and can be prevented by glucocorticoids
Asthma is caused by constriction of smooth muscle in bronchioles, leading to decreased diameter and treated with drugs that relax bronchiolar smooth muscle
Emphysema is characterized by destruction of alveolar walls and formation of large cyst-like sacs, reducing the surface area available for gas exchange and decreasing elasticity of the lungs

Ear

The ear is divided into three main parts: the external ear, the middle ear, and the inner ear.
The external ear consists of:
- The ear pinna, formed of elastic cartilage covered by thin skin, which directs sound waves to the inside.
- The external auditory meatus, a flattened canal extending from the ear pinna to the tympanic membrane, lined with skin containing hair follicles, sebaceous glands, and ceruminous glands that secrete a brownish semisolid wax.
The tympanic membrane (ear drum) is covered by simple cubical epithelium and transmits sound vibrations from the outer ear to the bony ossicles of the middle ear.

Eye

The eye wall consists of three main layers:
- The outer fibrous layer, which is supporting, consisting of:
  - Cornea, anterior (stratified squamous non-keratinized) epithelium.
  - Sclera, posterior (formed of dense irregular connective tissue).
- The middle vascular layer, which is vascular and pigmented, consisting of:
  - Iris.
  - Ciliary body.
  - Choroid.
- The inner nervous layer, consisting of:
  - Retina.
Eye color is determined by the amount of melanin in the iris pigmented epithelium on the back of the iris.
The ciliary body consists of:
- Two layers of epithelial cells: inner and outer cell layers.
- The inner layer is formed of non-pigmented cells.
- The outer layer is formed of pigmented cells.
The choroid:
- Has a black color.
- Functions to nourish the outer part of the retina.

Urinary System

The urinary system consists of two kidneys, two ureters, one urinary bladder, and one urethra.
The kidneys are responsible for excreting urine (approximately 1500-2000 ml/24 hours) containing metabolic waste products such as urea, creatinine, and uric acid.

Functions of the Kidneys

Regulate water and electrolyte balance and maintain acid-base balance.
Produce renin hormone that helps regulate blood pressure.
Produce erythropoietin hormone that stimulates the production of erythrocytes.
Hydroxylate vitamin D3 to its active form.

Structure of the Kidney

The stroma of the kidney consists of a capsule, reticular fibers, and few collagenous bundles.
The kidney is divided into lobes and lobules.
The parenchyma of the kidney is formed of urineferous tubules.

Urineferous Tubules

The cortex (outer) is red in color and contains Malpighian Renal Corpuscles.
The medulla (inner) is light grey in color and contains medullary rays and collecting tubules.

The Nephron

The nephron is the functional and structural unit of the kidney.
Each nephron consists of a Malpighian renal corpuscle, proximal and distal convoluted tubules, and the loop of Henle.
The Malpighian renal corpuscle forms the glomerular filtrate by the process of dialysis.

Malpighian Renal Corpuscle

Each corpuscle is formed of Bowman's Capsule, glomerular capillaries, supporting mesangial cells, and afferent and efferent arterioles.
Bowman's Capsule is a double-walled capsule surrounding the glomerular blood capillaries, formed of two continuous layers of epithelium separated by capsular space.
The parietal layer is formed of simple squamous epithelium, and the visceral layer is formed of modified simple squamous cells known as podocytes.

Podocytes

Podocytes have small foot-like processes (pedicles) that form a fenestrated epithelium around the fenestrated capillaries of the glomerulus.

Mesangial Cells

They are branched cells adherent to the surface of glomerular blood capillaries and act as structural support to podocytes and vessels.

Juxtaglomerular Complex

Present under the distal convoluted tubule (DCT), fitting between the afferent and efferent arterioles.

Proximal Convoluted Tubules vs. Distal Convoluted Tubules

Proximal convoluted tubules have a larger diameter, more apical microvilli, and reabsorb water, NaCl, Ca, phosphate, glucose, amino acids, and plasma proteins, while excreting creatinine, iodine, and penicillin.
Distal convoluted tubules have a smaller diameter, less apical microvilli, and reabsorb water and sodium while excreting sodium, potassium, and ammonium.

Female External Genitalia

Ovaries are covered by germinal epithelium and divided into cortex and medulla.
The ovarian cortex is composed of ovarian follicles in various stages of development.
The ovarian medulla is a richly vascularized fibroelastic connective tissue and hilus cells that secrete androgens.
If androgens increase in males, it will lead to sterility.

Ovarian Follicles

Ovarian follicles evolve through four developmental stages: primordial, primary, secondary, and Graafian follicles.
Primordial follicles are composed of a single layer of flattened follicular cells that surround the primary oocyte.
Primary follicles have two types: unilaminar and multilaminar, depending on the number of layers of follicular cells that surround the primary oocyte.
Multilaminar follicles secrete progestron and estrogen under FSH and lipids produce estrogen after menopause.
Secondary follicles are similar to primary follicles except for the presence of accumulations of liquor folliculi among the granulosa cells.
Graafian follicles, also known as mature follicles, undergo ovulation and may be as large as the entire ovary.

Ovulation

Ovulation is the process of releasing the secondary oocyte from the graafian follicle.
The corpus luteum is formed from the remnants of the graafian follicle and is a temporary endocrine gland that manufactures and releases hormones that support the uterine endometrium.

Oviducts (Fallopian Tubes)

The oviducts act as a conduit for spermatozoa to reach the primary oocyte and to convey the fertilized egg to the uterus.
The mucosa of oviduct is simple columnar epithelium partially ciliated and has two types of cells: columnar ciliated cells and peg cells.

Uterus

The uterus is a muscular organ consisting of a fundus, body, and cervix.
The uterine wall of the body and the fundus is composed of endometrium, myometrium, and adventitia or serosa.
The endometrium consists of two layers: a superficial functional layer (shed during menstruation) and a deeper basal layer.
The myometrium is composed of three smooth muscle layers: inner and outer longitudinal layers, and a middle circular (stratum vascularis) layer.

Cervix

The cervix is the terminal end of the uterus that protrudes to the vagina.
The upper cervix (endocervix) is lined by a simple columnar epithelium that contains mucous-secreting cells.
The lower cervix (ectocervix) is lined by a stratified squamous non-keratinizing epithelium.

Vagina

The vagina is lined by a stratified squamous non-keratinizing epithelium.

Male External Genitalia

The male external genitalia include the penis, urethra, and scrotum.
The internal male genitalia include the testes, epididymis, vas deferens, seminal vesicles, prostate, bulbo-urethral glands, and ejaculatory ducts.

Duct of Epididymis

The duct of epididymis is lined with pseudo-stratified columnar epithelium with stereocilia that increase the apical surface area.
The function of the duct of epididymis is absorption and storage of spermatozoa.

Vas Deferens

The vas deferens is formed of smooth muscles that convey spermatozoa to the ejaculatory duct during ejaculation.

Ejaculatory Duct

The ejaculatory duct is lined by folded simple columnar epithelium surrounded by connective tissue.
There is no muscle in the wall of the ejaculatory duct.

Penis

The penis is surrounded by erectile tissue and covered by keratinized stratified squamous epithelium.

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Description

This quiz covers the different parts of the digestive system, including the oral cavity, digestive tract, and digestive glands. Learn about the functions of the lips, tongue, palate, and cheeks in the digestive process.