Download respirotory practicle

Histology
Lec-10-
Ass. Lec.
Wafaa H. M. Alhashimy
Dentistry College
Second Stage
Respiratory System
Components of Respiratory System
A. Conducting Portion : consists of the nasal cavity, nasopharynx, larynx, trachea,
bronchi, bronchioles, and terminal bronchioles.
B. Respiratory Portion : consists of respiratory bronchioles, alveolar ducts, and alveoli.
The exchange of oxygen and carbon dioxide occurs within this portion.
Nasal Cavity
 The vestibules : are lined with a keratinised stratified squamous epithelium.
Hairs , which filter large particulate matter out of the airstream, and sebaceous
glands are also present.
 Conchae are bony, shelflike projections from the lateral wall within the nasal
cavity, the middle and inferior projections are lined with respiratory epithelium,
whereas the superior Conchae are lined by olfactory epithelium.
 The respiratory region (called respiratory epithelium) is lined with ciliated
pseudostratified columnar epithelium The respiratory segment has a very
vascularized lamina propria , both of which facilitate the conditioning
(warming, cooling and filtration) of the air. Mucous and serous glands in the
lamina propria .
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The olfactory segment :is located along the dorsal roof of the nasal cavity.
Mucosa : specialized type of pseudostratified columnar epithelium, known as
Olfactory epithelium consists of four distinct cell types:
-Olfactory cells :The olfactory cells of the epithelium are bipolar neurons
which congregate to form the olfactory nerve . The apical poles of these neurons
are covered with non-motile cilia, with the plasma membrane containing
odorant-binding proteins acting as olfactory receptors. The incoming odorants
are made soluble by the serous secretion from Bowman's Glands .
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-Supporting cells or Sustentacular cells are tall columnar cells featuring microvilli
support for the olfactory cells .
-Basal cells :Resting on the basal lamina of the olfactory epithelium, basal cells are
stem cells capable of division and differentiation into either supporting or olfactory
cells. The constant divisions of the basal cells leads to the olfactory epithelium being
replaced every 2–4 weeks.
-Brush Cells :a microvilli-bearing columnar cell with basal surface in contact with
afferent nerve endings, specialised for transduction of general sensation.
Lamina propria : contains Bowman's (Olfactory) Glands: are tubuloalveolar serous
secreting glands. The role of the secretions are to trap and dissolve odiferous
substances for the bipolar neurons. Constant flow from the Bowman's glands allows
old odors to be constantly washed away.
Paranasal sinuses are a group of four paired air-filled spaces that surround the nasal
cavity (maxillary sinuses), above the eyes (frontal sinuses), between the eyes (ethmoid
sinuses), and behind the ethmoids (sphenoid sinuses).
pharynx
The nasopharynx is the first part of the pharynx and continues caudally with the
oropharynx and hypopharynx . This region is lined by respiratory epithelium ,
Larynx
commonly called the voice box, is an organ involved in breathing, sound production,
and protecting the trachea against food aspiration. the larynx is found in the anterior
neck. The laryngeal skeleton consists of nine cartilages: three single (epiglottic,
thyroid and cricoid) and three paired .
The epiglottis is a flap that is made of elastic cartilage tissue covered with a mucous
membrane. It projects obliquely upwards behind the tongue and the hyoid bone,
pointing dorsally.
The vocal apparatus consists of two pairs of mucosal folds.
The false vocal folds are covered by respiratory epithelium, not responsible for sound
production, These false vocal folds do not contain muscle . while the true vocal folds
are covered by stratified squamous epithelium . have skeletal muscle.
Trachea
The trachea is a wide flexible tube, the lumen of which is kept open by 20 tracheal
cartilages, which are C-shaped rings of hyaline cartilage. The gaps between the rings
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of cartilage are filled by the trachealis muscle - a bundle of smooth muscle, and
fibroelastic tissue. Together these hold the lumen of the trachea open, but allow
flexibility during inspiration and expiration.
Mucosa and sub-mucosa of Trachea
The respiratory mucosa is made up of the epithelium and supporting lamina propria.
The epithelium is tall columnar pseudostratified with cilia and goblet cells. The
supporting lamina propria contains elastin, that plays a role in the elastic recoil of the
trachea during inspiration and expiration, together with blood vessels that warm the
air.
Branchial tree
A bronchus is a passage of airway in the respiratory tract that conducts air into the
lungs. The bronchus branches into smaller tubes, which in turn become bronchioles.
No gas exchange takes place in this part of the lungs.
The human trachea divides into two main bronchi , the left and the right, at the level
of the sternal angle
-The right main bronchus is wider, shorter, subdivides into three lobar bronchi .
-The left main bronchus divides into two lobar bronchi .
The lobar bronchi divide into tertiary bronchi. The segmental bronchi divide into
many primary bronchioles which divide into terminal bronchioles, each of which
then gives rise to several respiratory bronchioles, which go on to divide into two to 11
alveolar ducts. There are five or six alveolar sacs associated with each alveolar duct.
The alveolus is the basic anatomical unit of gas exchange in the lung.
The hyaline cartilage forms an incomplete ring in the bronchi, giving them a "D"shaped appearance in the larger bronchi and as small plates and islands in the smaller
bronchi. Smooth muscle is present continuously around the bronchi.
The cartilage and mucous membrane, the amount of hyaline cartilage in the walls
decreases until it is absent in the smallest bronchioles , the amount of smooth muscle
increases. The mucous membrane also undergoes a transition from ciliated
pseudostratified columnar epithelium to simple cuboidal epithelium to simple
squamous epithelium.
The alveolar ducts and alveoli consist primarily of simple squamous epithelium, which
permits rapid diffusion of oxygen and carbon dioxide. Exchange of gases between the
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air in the lungs and the blood in the capillaries occurs across the walls of the alveolar
ducts and alveoli.
Alveolar ducts are tiny ducts that connect the respiratory bronchioles to alveolar sacs,
They are tiny end ducts of the branching airways that fill the lungs. Each lung holds
approximately 1.5 to 2 million of them. The tubules divide into two or three alveolar
sacs at the distal end. They are formed from the confluence openings of several
alveoli. The epithelial lining consists of smooth muscle knobs covered by nonciliated,
simple cuboidal cells. The smooth muscle constricts under parasympathetic
innervation and relax under sympathetic innervatio.
Alveoli: Individual hollow cavities contained within alveolar sacs (or ducts). Alveoli
have very thin walls which permit the exchange of gases Oxygen and Carbon Dioxide.
They are surrounded by a network of capillaries, into which the inspired gases pass.
There are approximately 3 million alveoli within an average adult lung.
Diaphragm: The diaphragm is a broad band of muscle which sits underneath the
lungs, attaching to the lower ribs, sternum and lumbar spine and forming the base of
the thoracic cavity.
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