HUMAN ANATOMY

LECTURE EIGHTEEN

RESPIRATORY SYSTEM

FUNCTIONS

• Gas exchange - (O2 and CO2) in lungs

• Regulation of blood pH - alters blood CO2 levels

• Voice production - movement of air past vocal cords

• Immunity - protection against microorganisms by preventing

entry and removing them from respiratory surfaces

• Olfactory stimulation – airborne chemicals enter with

inhalation

TERMINOLOGY• Ventilation - movement of air into and out of lungs

• External respiration - gas exchange between air in lungs

and blood stream

• Internal respiration - gas exchange between blood and tissues

• Cellular respiration – production of energy (ATP) in the cell

RESPIRATORY ANATOMYUpper tract• Nose, nasal cavity, pharynx, and associated

structuresLower tract• Larynx, trachea, bronchi, and lungsRespiratory mucosa • lines the conducting portion• consists of epithelial cells with underlying areolar layer (lamina propria)• upper tract layer contains mucosa glands• lower tract layer contains bundles of smooth muscle cellsEpithelial layer changes:• pseudostratified ciliated columnar cells line

nasal cavity and pharynx, and portions of lower tract

• smaller bronchioles become cuboidal with some cilia• alveoli contain simple squamous epithelium

NOSE AND NASAL CAVITY• External nose composed of cartilage

with bone across the bridge• Nasal cavity extends from nares

through to choane (entrance to pharnyx)- hard palate makes up the floor and

separates nasal from oral cavity- nasal septum divides left and right

sides- conchae (3) are bony ridges on

lateral walls to increase surface area

- meatuses are areas between conchae- paranasal sinuses are air filled

spaces within bone that open into the nasal cavity and are lined with mucus membrane (reduce weight of skull, produce mucus, influence voice tone)

- nasolacrimal ducts (carry tears) also enter into cavity

- olfactory receptors found in superior area of nasal cavity

FUNCTIONS OF NASAL CAVITY• passageway for air

• trap debris from air:

- coarse hairs within epithelial lining (stratified squamous epithelium)

- pseudostratified columnar epithelium containing cilia and mucus

producing goblet cells - mucus traps debris and cilia sweep mucus to

pharynx (to be swallowed)

• air is warmed by nasal capillaries and moistened by mucus

• smell

• resonating chambers for speech

PHARYNX• Common passageway of

respiratory and digestive systems• Divided into three regions:(1) Nasopharynx

- internal nares to ulva- pseudostratified columnar

epithelium with goblet cells- auditory tubes enter- contains pharyngeal tonsils

(2) Oropharynx - ulva to epiglottis- stratified squamous

epithelium (protects against abrasion from food)

- palatine and lingual tonsils(3) Laryngopharynx

- from epiglottis to esophagus- lined with stratified squamous

and ciliated columnar epithelium

LARYNX

LARYNX• Found below hyoid bone in throat

• Consists of nine cartilages (three are unpaired and six form three pairs)

connected by muscles and ligaments

epiglottis is attached to thyroid and has flap near base of tongue (elastic

rather than hyaline cartilage)

• largest is the thyroid cartilage (Adam’s apple)

• most inferior is the cricoid cartilage – forms base of larynx

Vocal Cords

• held together by paired ligaments

- superior pair form the vestibular folds (false vocal cords)

- inferior pair form the vocal folds (true vocal cords)

FUNCTIONS OF LARYNX• Maintain an open passageway for air movement

• Epiglottis and vestibular folds prevent swallowed material from moving into larynx

• Vocal folds are primary source of sound production

- greater amplitude of vibration, louder the sound

- frequency of vibration determines pitch

VOCAL FOLDS

TRACHEA• Extends from the cricoid cartilage of

the larynx through the mediastium and divides into the right and left bronchi

• Membranous tube of dense connective tissue and smooth muscle (trachealis) supported by hyaline cartilage

• 16 to 20 C-shaped tracheal cartilage rings open posteriorly - provide protection and maintain open airway

• Lined with pseudostratified columnar epithelium with cilia and goblet cells that produce mucus – sweep mucus and debris upward so may be swallowed

BRONCHI• Trachea branches in mediastium into

right and left primary bronchi

• C-shaped cartilagenous rings maintain open airway

• Before branching each primary bronchus travels along the medial

groove (hilus) of the lung

BRONCHIAL TREE• Primary bronchi divide inside the lungs into smaller passageways - secondary

bronchi (two in the left and three in the right lung)

• Secondary bronchi divide into tertiary bronchi extending to the bronchopulmonary area of the lungs

• Walls of secondary and tertiary bronchi have progressively less cartilage and more smooth muscle - diameter decreases

- pseudostratified columnar epithelium with cilia and mucus producing goblet

cells

• Tertiary bronchi branch into bronchioles

and finally terminal bronchioles

• Terminal bronchioles branch into respiratory

bronchioles ending in alveolar ducts

- open into alveoli (small sacs)

- thin simple squamous epithelium

ALVEOLI• Each alveoli is surrounded by an

extensive capillary network

- capillaries are surrounded by a

network of elastic fibers to hold

alveoli and bronchioles and push

air out

• Alveolar epithelium is simple squamous epithelium - thin and very delicate for gas exchange

• Roaming macrophages patrol epithelial surface for foreign particles

• Septal cells produce superfactant (phospholipids and proteins) - to keep sacs open

RESPIRATORY MEMBRANE

• Site of gas exchange in alveoli

• Composed of:

(1) squamous cells lining alveoli

(2) endothelial cells lining adjacent

capillary

(3) fused basal laminae between

alveoli and endothelial cells

• Allows for quick exchange of O2 and CO2 across membrane

LUNGS• Each is cone-shaped with:

- base resting on diaphragm

- apex extending beyond clavicle

- hilus on medial surface is where

bronchi, blood vessels, nerves, and

lymphatics enter - form root

• Divided into lobes (right has three and left has two) separated by deep fissures

• Each lobe is divided into bronchopumonary segments separated by a connective tissue septa - supplied by tertiary bronchi

- divided into lobules - supplied by bronchioles

PLEURA• Lungs sit inside thoracic cavity

• Each lung is surrounded by a separate pleural cavity filled with pleural fluid (lubricant holds membranes close together)

• Each cavity is lined with a serous membrane called pleura

visceral pleura - adheres to lung

parietal pleura - adheres to thoracic wall

THORACIC WALL• Thoracic vertebrae, ribs, costal cartilages, sternum and associated muscles

• Thoracic cavity is the space enclosed by the thoracic wall and the diaphragm

• Diaphragm separates thoracic cavity from abdominal cavity