BMS 251 - Exam #3

Functions of respiratory system

Respiration (Oxygen and CO2 exchange between atmosphere and body cells)

Ventilation (Breathing)

Pulmonary Gas Exchange (External Respiration)

Tissue Gas Exchange (Internal Respiration)

Cellular Respiration

General functions of respiratory system

Air passageway

Site of exchange O2 and CO2

Detection of odors

Sound production

Structural organization of RS

Upper and lower respiratory tracts

Functional organization of RS

Conducting and respiratory zone

Structure of mucosa membrane

Respiratory tract: Psuedostratified ciliated columnar epithelium

Traps foreign particles (mucus) and removes trapped particles out of respiratory tract (cilia)

From nasal cavity to alveoli, epithelium gets thinner

Regions of the nasal cavity

Olfactory region

Respiratory region

Nasal vestibule

Olfactory region

Detects odors

Olfactory epithelium is in mucus membrane

Contains olfactory receptors to detect odors

Respiratory region

Conditions incoming air

Conchae: produce turbulence in inhaled air to increase contact of air with mucosa (warm, cleanse, humidify)

Nasal vestibule

Traps large particulates

Vibrissae: course hair that serve to trap inhaled pathogens & debris

Function of pharynx

Passageway for air and food

Mucosa and tonsils protect from ingested substances

Eustachian tubes equalize pressure on either side of tympanic membranes

Three regions of pharynx

Nasopharynx: Respiratory only, leads to auditory tubes, pharyngeal tonsils, psuedostratified ciliated columnar epithelium

Oropharynx: Respiratory and digestive, lingual and palatine tonsils, nonkenatinized stratified squamous epithelium

Laryngopharynx: Respiratory and digestive, nonkenatinized stratified squamous epithelium

Structure and function of larynx

Inferior to pharynx, superior to trachea

Passageway for air, prevent aspiration of ingested material, speech, sneeze/cough reflex, valsalva manuever

How does the larynx contribute to sound production?

Exhaled air vibrates the vocal folds

Structure and function of the trachea

Windpipe

Inferior to larynx, anterior to espohagus

Carries oxygen

Has cartilage rings

Structural subdivisions of bronchial tree

Main bronchi

Lobar bronchi

Segmental bronchi

Smaller bronchi

Location and function of smooth muscle in bronchial tree

Transitions to smooth muscle in bronchioles

To allow for bronchocontriction and bronchodilation

Bronchoconstriction

Limits airflow in bronchial tree

Limits entry of harmful substances

Bronchodilation

Maximizes airflow in bronchial tree

Maximizes O2 delivery and CO2 removal

Sympathetic NS

Terminal bronchiole

Epithelium and smooth muscle

Marks the transition from conducting zone into respiratory zone

Respiratory bronchiole

Thin walls, sparse alveoli, smooth muscle

Transport air and begin gas exchange

Alveolar ducts

Thin walls, smooth muscle

Pathway to alveolar sacs

Alveoli

Simple squamous epithelium surrounded by capillaries

Primary site of gas exchange

Alveolar Type I cells

Facilitate rapid diffusion of gases

Alveolar Type II cells

Provide surfactant to reduce surface tension and prevent collapse

How do alveoli provide surface area for pulmonary capillaries?

Act as microscopic balloon-like sacs to create a highly-vascularized network

Structure and function of respiratory membrane

Alveolar-capillary membrane

Function is pulmonary gas exchange (oxygen and CO2 exchange)

Pleural membrane

Two thin membranes (visceral (inside) and parietal (outside)) that enclose the lungs and line the chest cavity to create a fluid-filled space for breathing

Pleural cavity

Fluid-filled space between parietal and visceral membranes

How does pleural membrane keep lungs inflated?

Creating a low-pressure cavity to create a suction membrane. Elastic recoil allows stretch and inward pull

Bronchopulmonary segments of lungs

Functional units of the lungs

Encapsulated in connective tissue supplied by own segmental bronchus, branch of pulmonary artery & vein.

Respiration

The movement of respiratory gases between atmosphere and systemic cells of the body (pulmonary ventilation, pulmonary gas exchange, gas transport, tissue gas exchange)

Pulmonary ventilation

Movement of gases between atmosphere & alveoli

Pulmonary gas exchange

Exchange of gases between alveoli & the blood in pulmonary capillaries

Gas transport

Transport of gases in the blood to the systemic cells of the body

Tissue as exchange

Exchange of gases between blood in systemic capillaries and systemic cells of the body

Ventilation

Moving air in and out of the lungs to facilitate gas exchange

Physiological process of pulmonary ventilation

Inspiration and expiration driven by pressure differences

Quiet breathing

Rhythmic breathing at rest

Forced breathing

Vigorous breathing during exercise

Four steps of pulmonary ventilation

1. Autonomic nuclei in brainstem control skeletal muscles of breathing
2. Muscles of breathing contract/relax to change volume of thoracic cavity
3. Volume changes in thoracic cavity establish pressure gradient between lungs & atmosphere
4. Air moves down the pressure gradient

How are pressure gradients established by skeletal muscles?

By changing the pressure in the thoracic cavity

Inspiration expands thoracic cavity

Expiration shrinks thoracic cavity

Boyle’s Law

Inverse relationship between pressure and volume

If volume increases, pressure decreases

If volume decreases, pressure increases

Nervous system structures involved in breathing

Medullary respiratory center (ventral and dorsal)

Pontine respiratory center

Physiological events of quiet breathing

Sensors (chemoreceptors, central and peripheral)

Respiratory center

Respiratory muscles

How is pulmonary ventilation controlled by CNS?

Chemoreceptors send signals to ventral respiratory center to control rate and depth of breathing

What is the difference between central and peripheral chemoreceptors?

Central detects CO2 in CSF

Peripheral receptors detect low O2 and pH

Other reflexes that alter breathing rate and depth

Mechanoreceptors (detect stretch in lungs, prevent over-inflation, receptors send signals to respiratory center to stop inhalation)

Proprioceptors (stimulated by skeletal muscle movement, more movement = greater breathing depth)

Irritant receptors (stimulated by pain/inhaled particles, causes sneezing/coughing)

Airflow

The amount of air that moves into and out of the respiratory tract with one breath

How do pressure gradients and resistance determine airflow?

The difference in interpulmonary pressure and atmospheric pressure and resistance from elasticity of lungs control airflow

Partial pressure

The amount of pressure each gas contributes to the total pressure
within a mixture of gases

How do total pressure and % of gas impact partial pressure?

If total gas increases while gas concentration stays the same, partial pressure decreases. If % of gas increases while total gas stays the same, partial pressure increases.

Partial pressure gradient

A difference in the partial pressure of one specific gas between two locations

Will diffuse down partial pressure gradients to even out concentration

Pulmonary gas exchange

Passive diffusion of oxygen (O2) into and carbon dioxide (CO2) out of pulmonary capillaries across the respiratory membrane, driven by partial pressure differences.

Anatomic features of respiratory membrane for efficient breathing

Large surface area

Extremely thin membrane

Ventilation-perfusion coupling

The matching of air flow (ventilation) to blood flow (perfusion) in pulmonary alveoli to maximize oxygen uptake and carbon dioxide removal.

Ensures that well-ventilated areas receive high blood flow, while poorly ventilated areas are bypassed, optimizing efficient gas exchange

Tissue gas exchange

The process where oxygen diffuses from systemic capillaries into body tissues and carbon dioxide diffuses from tissues into the bloodstream.

Pulmonary v. tissue gas exchange

Pulmonary oxygenates blood

Tissue delivers oxygenated blood to cells and removes CO2

Why does partial pressure in the blood change depending on location?

More oxygen is necessary in certain parts of the body

Why is hemoglobin essential to oxygen transport?

Carries more oxygen than plasma can dissolve

How is CO2 transported in the blood?

Dissolved in plasma

Bound to amino groups in hemoglobin

Transported in plasma as bicarbonate

Conversion of CO2 to HCO3-

CO2 diffuses into erythrocytes

Carbonic anhydrase catalyzes formation of HCO3-

HCO3- leaves erythrocyte and moves into plasma

Three substances carried by hemoglobin

O2

CO2

Nitric oxide (NO)

Most important variable that influences binding of O2 to hemoglobin

Partial pressure of oxygen

How do variables that increase metabolism impact hemoglobin?

Increased metabolism (lower pH, high PCO2, high temp) cause hemoglobin to release oxygen molecules

Hormones that active feeding center

Ghrelin (stomach

Hormones that activate satiety center

CCK (small intestine)

Insulin (pancreas)

Leptin (adipose tissue)

Organs of the GI tract

Oral cavity

Pharynx

Esophagus

Stomach

Small intestine

Large intestine

Anal canal

Accessory digestive organs

Teeth

Tongue

Salivary glands

Liver

Gallbladder

Pancreas

Functions of digestive system

Ingestion (entry of substance)

Motility (mix and move substance through GI tract)

Secretion (release of substances to aid in digestion)

Digestion (breakdown of substances)

Absorption (transport of materials to lymph or blood)

Elimination (excretion of undigested components)

Digestion

Mechanical: physically making food smaller (chewing, stomach churning)

Chemical: use of enzymes to break down complex molecules into simple molecules

Motility

Smooth muscle in the wall of GI tract contract and relax to move GI contents

Segmentation: mixing

Perstalsis: wave of contraction

Absorption

Digested substances are transported from the lumen of the GI tract through epithelium

Most absorbed through blood

Lipids and lipid-soluble vitamins absorbed in lymph

Systems that regulate digestive system

Nervous system (enetric and autonomic, parasympathetic/sympathetic)

Endocrine system

Location of ENS

Neurons and glis embedded in gut wall as ganglia

Innervate smooth muscle and glands of GI tract

Location of ANS

Innervates muscle and glands of GI tract (direct control)

Neurons of ENS (indirect control)

Sympathetic - decreases activity

Parasympathetic - increases activity

Short reflex

Local, only involves ENS

Alters GI activity in local segment of tract

Long reflex

Involves CNS & ANS

Alters activity in most of GI tract & accessory organs

Receptors in the digestive system

Chemoreceptors (chemical, trigger digestive enzymes)

Baroreceptors (physical, detect stretch)

Located in mucosa and submucosa walls

Mastication

Chewing

Composition and function of saliva

99.5% water, 0.5% solutes (enzymes, mucin, lysozyme and antibodies)

Moisten food, chemical digestion, cleanse oral cavity, prevent bacterial growth

How stomach participates in digestion

Holds place for ingested food

Chemical & mechanical digestion

Absorption

Regulates entry of chyme in small intestine

Secretory cells in gastric epithelium

Surface mucous cell

Mucous neck cell

Parietal cell

Chief cell

G-cell

Secretions of gastric cells

Alkaline mucus - coat inner stomach, protect from acidity

HCl - breaks down plant walls and denatures proteins, activates enzymes, creates optimal pH from pepsin and acidic lipases

Gastric lipase - digests fats, active in low pH of stomach

Pepsinogen - breaks down denatured enzymes, active in low pH of stomach

Gastrin - hormone released into blood, stimulates stomach motility and secretions

Cephalic reflex

Sensory input and thoughts of food sent to medulla oblongata

Medulla integrated into and increases PS output to stomach

Stomach increases contractions and secretions

Gastric reflex

Baro & chemoreceptors in stomach are activated and send info to medulla oblongata

Medulla processes info and increases PS output to stomach

Stomach increases contractions and secretions

Intestinal reflex

Chemoreceptors in small intestine are activated and send info to medulla

Medulla processes info to decreases PS output to stomach

Stomach decreases contractions and secretions

Primary function of small intestine

Finishes chemical digestion

Primary site for absorption of nutrients and water

Function of circular folds

Increase surface area, slow down movement of food

Function of villi and microvilli

Increase surface area for absorption

Small intestine secretion cells

Simple columnar epithelium: absorbs nutrients

Goblet cells: produces mucin

Enter endocrine cell: secretes CCK & secretin

Paneth cell: secretes lysozome

Liver in the digestive process

Produce bile

Pancreas in the digestive process

Releases pancreatic juices which chemically digest all macromolecules and neutralize acidic chyme

Gallbladder in digestive process

Store and release bile into duodenum

Function of bile

Neutralize acidic chyme

Emulsification of lipids (bile salts)

Elimination of bilirubin & cholesterol

Regulation of accessory glands

Secretin & CCK and autonomic nervous system

Motility in the small intestine

Segmentation dominates early intestinal phase (mixes chyme with accessory digestive secretions & brush border enzymes)

Peristalisis dominates late intestinal phase (propel chyme towards the large intestine)

Gastroileal reflex

Initiated during gastric & intestinal phase

Ileum contracts

Ileocecal valve relaxes

GI contents enter cecum

Primary function of large intestine

Absorption of remaining water & electrolytes

Vitamin synthesis by colonic bacteria (K & B5)

Formation, storage, and elimination of feces

Peristalsis in large intestine

Slow

Short reflex

Haustral churning in large intestine

Hastrum stretches as it fills with fecal material

Stretch stimulates contraction of hastrum

Mixes and moves material to distal hastra

Short reflex