Basic Functions of the Respiratory System

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The Respiratory System

•Basic functions of the respiratory system

•Supplies body with oxygen

•Disposes of carbon dioxide

•Four processes involved in respiration

•Pulmonary ventilation

•External respiration

•Transport of respiratory gases

•Internal respiration

Functional Anatomy of the Respiratory System

•Respiratory organs

•Nose, nasal cavity, and paranasal sinuses

•Pharynx, larynx, and trachea

•Bronchi and smaller branches

•Lungs and alveoli

Organs of the Respiratory System

•Divided into

•Conducting zone

•Respiratory zone

The Nose

•Provides an airway for respiration

•Moistens and warms air

•Filters inhaled air

•Resonating chamber for speech

•Houses olfactory receptors

The Nose

•Size variation due to differences in nasal cartilages

•Skin is thin—contains many sebaceous glands

The Nasal Cavity

•External nares—nostrils

•Divided by nasal septum

•Continuous with nasopharynx

•Posterior nasal apertures—choanae

Nasal Cavity

•Two types of mucous membrane

•Olfactory mucosa

•Near roof of nasal cavity

•Houses olfactory (smell) receptors

•Respiratory mucosa

•Lines nasal cavity

•Epithelium is pseudostratified ciliated columnar

The Upper Respiratory Tract

Respiratory Mucosa

•Consists of

•Pseudostratified ciliated columnar epithelium

•Goblet cells within epithelium

•Underlying layer of lamina propria

•Cilia move contaminated mucus posteriorly

Nasal Conchae

•Superior and middle nasal conchae

•Part of the ethmoid bone

•Inferior nasal conchae

•Separate bone

•Project medially from the lateral wall of the nasal cavity

•Particulate matter

•Deflected to mucus-coated surfaces

The Pharynx

•Funnel-shaped passageway

•Connects nasal cavity and mouth

•Divided into three sections by location

•Nasopharynx

•Oropharynx

•Laryngopharynx

•Type of mucosal lining changes along its length

The Nasopharynx

•Superior to the point where food enters

•Only an air passageway

•Closed off during swallowing

•Pharyngeal tonsil (adenoids)

•Located on posterior wall

•Destroys entering pathogens

•Contains the opening to the pharyngotympanic tube (auditory tube)

•Tubal tonsil

•Provides some protection from infection

The Oropharynx

•Arch-like entranceway—fauces

•Extends from soft palate to the epiglottis

•Epithelium

•Stratified squamous epithelium

•Two types of tonsils in the oropharynx

•Palatine tonsils—in the lateral walls of the fauces

•Lingual tonsils—covers the posterior surface of the tongue

The Laryngopharynx

•Passageway for both food and air

•Epithelium

•Stratified squamous epithelium

•Continuous with the esophagus and larynx

The Respiratory System

The Larynx

•Three functions

•Voice production

•Provides an open airway

•Routes air and food into the proper channels

•Superior opening is

•Closed during swallowing

•Open during breathing

Nine Cartilages of the Larynx

•Thyroid cartilage

•Shield-shaped, forms laryngeal prominence (Adam’s apple)

•Three pairs of small cartilages

•Arytenoid cartilages

•Corniculate cartilages

•Cuneiform cartilages

•Epiglottis

•Tips inferiorly during swallowing

The Larynx

•Vocal ligaments of the larynx

•Vocal folds (true vocal cords)

•Act in sound production

•Vestibular folds (false vocal cords)

•No role in sound production

•Epithelium of the larynx

•Stratified squamous—superior portion

•Pseudostratified ciliated columnar—inferior portion

The Larynx

•Voice production

•Length of the vocal folds changes with pitch

•Loudness depends on the force of air across the vocal folds

•Sphincter function of the larynx

•Valsalva’s maneuver—straining

•Innervation of the larynx

•Recurrent laryngeal nerves (branch of vagus)

The Trachea

•Descends into the mediastinum

•C-shaped cartilage rings keep airway open

•Carina

•Marks where trachea divides into two primary bronchi

•Epithelium

•Pseudostratified ciliated columnar

The Trachea

Bronchi in the Conducting Zone

•Bronchial tree

•Extensively branching respiratory passageways

•Primary bronchi (main bronchi)

•Largest bronchi

•Right main bronchi

•Wider and shorter than the left

Bronchi in the Conducting Zone

•Secondary (lobar) bronchi

•Three on the right

•Two on the left

•Tertiary (segmental) bronchi

•Branch into each lung segment

•Bronchioles

•Little bronchi, less than 1 mm in diameter

•Terminal bronchioles

•Less than 0.5 mm in diameter

Changes in Tissue Composition along Conducting Pathways

•Supportive connective tissues change

•C-shaped rings replaced by cartilage plates

•Epithelium changes

•First, pseudostratified ciliated columnar

•Replaced by simple columnar, then simple cuboidal epithelium

•Smooth muscle becomes important

•Airways widen with sympathetic stimulation

•Airways constrict under parasympathetic direction

Structures of the Respiratory Zone

•Consists of air-exchanging structures

•Respiratory bronchioles—branch from terminal bronchioles

•Lead to alveolar ducts

•Lead to alveolar sacs

Structures of the Respiratory Zone

•Alveoli

•~300 million alveoli account for tremendous surface area of the lungs

•Surface area of alveoli is ˜140 square meters

Structures of the Respiratory Zone

•Structure of alveoli

•Type I cells—single layer of simple squamous epithelial cells

•Surrounded by basal lamina

•Alveolar and capillary walls plus their basal lamina form

•Respiratory membrane

Structures of the Respiratory Zone

•Structures of alveoli (continued)

•Type II cells—scattered among type I cells

•Are cuboidal epithelial cells

•Secrete surfactant

•Reduces surface tension within alveoli

•Alveolar macrophages

Expiration

•Quiet expiration—chiefly a passive process

•Inspiratory muscles relax

•Diaphragm moves superiorly

•Volume of thoracic cavity decreases

•Forced expiration—an active process

•Produced by contraction of

•Internal and external oblique muscles

• Transverse abdominis muscles

Changes in Thoracic Volume

The Digestive System

Overview of the Digestive System

•Organs are divided into two groups

•Alimentary canal

•Mouth, pharynx, and esophagus

•Stomach, small intestine, and large intestine

•Accessory digestive organs

•Teeth and tongue

•Gallbladder, salivary glands, liver, and pancreas

•Accessory organs are connected to the alimentary canal by ducts

•Secretions contribute to breakdown of foodstuffs

The Alimentary Canal and Accessory Digestive Organs

Digestive Processes

•Ingestion—occurs in the mouth

•Propulsion—movement of food

•Peristalsis—major means of propulsion

•Mechanicaldigestion—prepares food for chemical digestion

•Chewing, churning food in stomach, segmentation

•Segmentation is rhythmic local constrictions of intestine

Digestive Processes

•Chemical digestion—complex molecules broken down to chemical components

•Mouth

•Stomach

•Small intestine

•Absorption—transport of digested nutrients

•Defecation—elimination of indigestible substances as feces

Digestive Processes

Peristalsis

•Major means of propulsion

•Adjacent segments of the alimentary canal relax and contract

Segmentation

•Rhythmic local contractions of the intestine

•Mixes food with digestive juices

Abdominal Regions

•Four lines divide abdominal wall into nine regions

•Midclavicular lines—vertical lines of grid

•Subcostal plane—superior horizontal line

•Connects inferior points of costal margin

•Transtubercular plane—inferior horizontal line

•Connects tubercles of iliac crests

Nine Regions of Anterior Abdominal Surface

•How regions relate to abdominal viscera

Abdominal Quadrants

•A simpler method of sectioning the anterior abdominal wall

•Right upper quadrant

•Left upper quadrant

•Right lower quadrant

•Left lower quadrant

The Peritoneal Cavity and Peritoneum

•Peritoneum—a serous membrane

•Visceral peritoneum—surrounds digestive organs

•Parietal peritoneum—lines the body wall

•Peritoneal cavity—a slit-like potential space

The Peritoneal Cavity and Peritoneum

•Mesentery—a double layer of peritoneum

•Holds organs in place

•Sites of fat storage

•Provides a route for circulatory vessels and nerves

The Peritoneal Cavity and Peritoneum

•Retroperitoneal organs

•Behind the peritoneum

•Peritoneal organs

•Digestive organs that keep their mesentery

Mesenteries

•Superficial view of abdominal organs

Mesenteries

•Lesser omentum attaches to lesser curvature of stomach

Mesenteries

•Greater omentum—a “fatty apron” of peritoneum

•Greater omentum and transverse colon reflected

Mesenteries

•Sagittal section through the abdominopelvic cavity

•Mesenteries attach to posterior abdominal wall

Secondarily Retroperitoneal Organs

•Initially formed within peritoneum

•Become retroperitoneal

•Fuse to posterior abdominal wall

Summary of Intraperitoneal and Secondarily Retroperitoneal Organs

Histology of the Alimentary Canal Wall

•Same four layers from esophagus to anus

•The mucosa—innermost layer

•Consists of

•Epithelium

•Lamina propria

•Muscularis mucosae

•The submucosa—external to the mucosa

•Contains blood and lymphatic vessels, nerve fibers

Histology of the Alimentary Canal Wall

•The muscularis externa—external to the submucosa

•Two layers

•Circular muscularis—inner layer

•Longitudinal muscularis—outer layer

•The serosa—the outermost layer

•Is the visceral peritoneum

Smooth Muscle

•Primarily found in walls of viscera

•Fibers elongated

•Have one centrally located nucleus

•Grouped into sheets

•Longitudinal layer—parallel to long axis of organ

•Circular layer—deeper layer, fibers run around circumference of organ

Smooth Muscle Contraction

•Myofilaments operate by interaction with cytoskeleton

•Dense bodies—correspond to Z-discs of skeletal muscle

Innervation of Smooth Muscle

•Innervated by ANS

•Few fibers per sheet innervated

•Sheet of smooth muscle contracts as a unit

•Exceptions

•Iris of eye

•Arrector pili muscles in skin

Nerve Plexuses

•Myenteric nerve plexus

•Lies between circular and longitudinal muscularis

•Controls peristalsis and segmentation

•Submucosal nerve plexus

•Lies in submucosa

•Signals glands to secrete

•Innervation

•Sympathetic and parasympathetic motor fibers

•Visceral sensory fibers

The Digestive System

The Mouth and Associated Organs

•The mouth—oral cavity

•Mucosal layer

•Stratified squamous epithelium

•Lamina propria

•The lips and cheeks

•Formed from orbicularis oris and buccinator muscles, respectively

Anatomy of the Mouth

•The labial frenulum

•Connects lips to gum

•The palate

•Forms the roof of the mouth

The Tongue

•Interlacing fascicles of skeletal muscle

•Grips food and repositions it

•Helps form some consonants

•Intrinsic muscles—within the tongue

•Extrinsic muscles—external to the tongue

•Lingual frenulum

•Secures tongue to floor of mouth

The Superior Surface of the Tongue

•Tongue papillae

•Filiform papillae—no taste buds

•Fungiform papillae

•Circumvallate papillae

•Sulcus terminalis

•Marks border between mouth and pharynx

•Posterior one-third of tongue lies in oropharynx

•Lined with lingual tonsil

The Teeth

•Deciduous teeth—20 teeth

•First appear at 6 months of age

•Permanent teeth—32 teeth

•Most erupt by the end of adolescence

•Dental formula—shorthand

•Way to indicate number and position of teeth

•2I, 1C, 2P, 3M

Tooth Structure

•Longitudinal section of tooth in alveolus

The Salivary Glands

•Produce saliva

•Compound tubuloalveolar glands

•Parotid glands

•Parotid duct—parallel to zygomatic arch

•Contains only serous cells

•Submandibular glands

•Lies along medial surface of mandible

•Sublingual glands

•Lies in floor of oral cavity

•Contains primarily mucous cells

The Salivary Glands

The Pharynx

•Oropharynx and laryngopharynx

•Passages for air and food

•Lined with stratified squamous epithelium

•External muscle layer

•Consists of superior, middle, and inferior pharyngeal constrictors

The Esophagus

•Gross anatomy—muscular tube

•Begins as a continuation of the pharynx

•Joins the stomach inferior to the diaphragm

•Cardiac sphincter—closes lumen to prevent stomach acid from entering esophagus

The Esophagus

•Microscopic anatomy

•Epithelium is stratified squamous epithelium

•When empty, mucosa and submucosa in longitudinal folds

•Mucous glands—primarily compound tubuloalveolar glands

•Muscularis externa

•Skeletal muscle first third of length

•Adventitia—most external layer

The Stomach

•Site where food is churned into chyme

•Secretion of pepsin begins protein digestion

•Functions under acidic conditions

•Food remains in stomach approximately 4 hours

•Regions of the stomach

•Cardiac region

•Fundus

•Body

•Pyloric region

Microscopic Anatomy of the Stomach

•Muscularis has three layers

•Circular and longitudinal layers and oblique layer

•Epithelium is simple columnar epithelium

•Mucosa dotted with gastric pits

•Gastric glands—deep to gastric pits

Microscopic Anatomy of the Stomach

•Gastric glands of fundus and body

•Mucous neck cells

•Secrete a special mucus

•Parietal (oxyntic) cells

•Secrete hydrochloric acid and gastric intrinsic factor

•Chief (zymogenic) cells

•Secrete pepsinogen

•Pepsinogen is activated to pepsin when it encounters acid in the gastric glands

The Small Intestine—Gross Anatomy

•Longest portion of the alimentary canal

•Site of most enzymatic digestion and absorption

•Three subdivisions

•Duodenum

•Jejunum

•Ileum

•Innervation

•Parasympathetic fibers from vagus nerve

•Sympathetic from thoracic splanchnic nerves

The Duodenum

•Receives digestive enzymes and bile

•Main pancreatic duct and common bile duct enter duodenum

•Sphincters control entry of bile and pancreatic juices

The Small Intestine—Microscopic Anatomy

•Modifications for absorption

•Circular folds (plicae circulares)

•Transverse ridges of mucosa and submucosa

•Villi

•Finger-like projections of the mucosa

•Covered with simple columnar epithelium

•Microvilli

•Further increase surface area for absorption

Histology of the Intestinal Wall

•Absorptive cells

•Uptake digested nutrients

•Goblet cells

•Secrete mucus that lubricates chyme

•Enteroendocrine cells

•Secrete hormones

•Intestinal crypts

•Epithelial cells secrete intestinal juice

The Digestive System

The Large Intestine

•Digested residue contains few nutrients

•Small amount of digestion by bacteria

•Main functions

•Absorb water and electrolytes

•Mass peristaltic movements force feces toward the rectum

Gross Anatomy of Large Intestine

•Subdivided into

•Cecum, vermiform appendix, colon, rectum, anal canal

•Special features of large intestine

•Teniae coli

•Thickening of longitudinal muscularis

•Haustra

•Puckering created by teniae coli

•Epiploic appendages

•Fat-filled pouches of visceral peritoneum

Gross Anatomy of Large Intestine

•Cecum

•Blind pouch

•Beginning of large intestine

•Vermiform appendix

•Contains lymphoid tissue

•Neutralizes pathogens

•Colon

•Divided into distinct segments

•Ascending, transverse, descending, and sigmoid colon

Gross Anatomy of Large Intestine

•Rectum

•Descends along the inferior half of the sacrum

•Anal canal

•The last subdivision of the large intestine

•Lined with stratified squamous epithelium

Vessels and Nerves of the Large Intestine

•First half of large intestine

•Arterial supply—superior mesenteric artery

•Innervation

•Sympathetic innervation—superior mesenteric and celiac ganglia

•Parasympathetic innervation—vagus nerve

Vessels and Nerves of the Large Intestine

•Distal half of large intestine

•Arterial supply—inferior mesenteric artery

•Innervation

•Sympathetic innervation—inferior mesenteric and hypogastric plexuses

•Parasympathetic innervation—pelvic splanchnic nerves

Microscopic Anatomy of Large Intestine

•Villi are absent

•Contains numerous goblet cells

•Intestinal crypts—simple tubular glands

•Lined with simple columnar epithelial tissue

•Epithelium changes at anal canal

•Becomes stratified squamous epithelium

The Liver

•Largest gland in the body

•Performs over 500 functions

•Digestive function

•Bile production

•Performs many metabolic functions

The Liver

Microscopic Anatomy of the Liver

•Hepatocyte—functional cells of the liver

•Portal triad composed of

•Bile duct tributary

•Branch of hepatic portal vein

•Branch of hepatic artery

•Kupffer cells—destroy bacteria

Microscopic Anatomy of the Liver

•Some functions of hepatocytes

•Rough ER manufactures blood proteins

•Smooth ER produces bile salts, detoxifies poisons

•Peroxisomes detoxify poisons (alcohol)

•Golgi apparatus packages secretory products

•Mitochondria provide energy for liver processes

•Glycosomes store sugar

•Great capacity for regeneration

The Gallbladder

•Stores and concentrates bile

•Expels bile into duodenum

•Bile emulsifies fats

•Cholecystokinin—released from enteroendocrine cells in response to fatty chyme

The Gallbladder

The Digestive System

The Pancreas

•Exocrine function

•Acinar cells make, store, and secrete pancreatic enzymes

•Enzymes are activated in the duodenum

•Endocrine function

•Produces insulin and glucagon

•Regulates blood sugar

The Exocrine Pancreas: Histology

Peptic Ulcers

•Are erosions of the mucosa of a region of the alimentary canal

•Gastric ulcers

•Occur in pyloric region of the stomach

•Duodenal ulcers

•Occur in duodenum of the small intestine

Peptic Ulcers

•Caused by Helicobacter pylori

•H. pylori

•Acid-resistant

•Binds to gastric epithelium

•Induces oversecretion of acid and inflammation

Peptic Ulcers

Disorders of the Digestive System

•Intestinal obstruction

•Mechanical obstructions

•Adhesions, tumors, or foreign objects

•Nonmechanical obstruction

•Halt in peristalsis

•Trauma

•Intestines touched during surgery

Disorders of the Digestive System

•Inflammatory bowel disease

•Inflammation of intestinal wall

•Crohn’s disease

•Ulcerative colitis

•Viral hepatitis

•Jaundice and flu-like symptoms

•Major types—A, B, C, and G

Disorders of the Digestive System

•Cystic fibrosis and the pancreas

•Pancreatic ducts become blocked with mucus

•Clogged ducts prevent pancreatic juices from entering small intestine

•Leads to malabsorption of fats and other nutrients

Embryonic Development of the Digestive System

•Alimentary canal formed in week 3

•Encloses tubular portion of yolk sac

•Vitelline duct

•Landmark dividing into three regions

•Forgut

•Midgut

•Hindgut

Embryonic Development of the Digestive System

The Digestive System in Later Life

•Middle age—gallstones and ulcers

•Old age—activity of digestive organs decline

•Fewer digestive juices and enzymes produced

•Absorption is less efficient

•Dehydration of fecal mass leads to constipation

•Diverticulosis and cancer of digestive organs

The Urinary System

•Important functions of the kidneys

•Maintain the chemical consistency of blood

•Filter many liters of fluid from blood