Sue Lee (sjl2005)
Sara Nash (sas2007)
RESPIRATORY SYSTEM
Overview
The function of the respiratory system is to exchange gases between the body and the surrounding
environment. However, one would not want their lungs to open directly into the environment, as this
exposure would predispose to infection, deposition of potentially toxic substances, and would furthermore
jeopardize the body’s ability to maintain a stable body temperature.
The respiratory system avoids these problems by having two parts. The gross and microscopic
structure of these zones are different and reflect their specific function.
1. Conducting Zone- for warming, moistening, and filtering
2. Respiratory Zone- for gas exchange
I. Conducting Zone
A. Function- warm, moisten, filter air
B. Anatomy
1. trachea- C-shaped rings of hyaline cartilage which keep the airway open,
especially during expiration. Note that the rings are open posteriorly to allow the
esophagus room to expand during peristalsis.
2. bronchi- cartilaginous plates instead of rings
3. bronchioles (large bronchioles→ small→ terminal)- smooth muscle, collagen, and
reticular fibers for support. NO cartilage.
C. Cell Types- the cellularity of the conducting airways changes as you approach the respiratory
airways. As you proceed from trachea to terminal bronchiole, glandular tissue disappears, as
do brush cells and goblet cells. Clara cells are found at the very end of terminal bronchioles,
and at this transition point the ciliated pseudostratified epithelium can change into simple
ciliated columnar or even simple non-ciliated cuboidal epithelium.
1. Ciliated columnar pseudostratified epithelium- consists of the columnar ciliated
cells that are responsible for driving a mucus flow outward (i.e. toward the pharynx)
along the lumen wall; and basal cells that are undifferentiated cells found near the
basement membrane, don’t extend to lumen, can develop into ciliated or goblet cells.
2. Goblet cells- secrete mucus. Found scattered in epithelium from nose to bronchi.
3. Brush cells- sensory cells with microvilli, found in trachea (and occasionally in
alveoli) and thought to be involved in cough and sneeze reflexes.
4. Clara cells- non-ciliated. In the conducting system, found only in the transition from
terminal bronchiole to respiratory bronchiole. Secrete “surface-active agent” which
helps prevent lumenal collapse.
5. Neuroepithelial (APUD) cells- involved in sensory processes, secrete serotonin and
substance P, which have effects on smooth muscle. Found in clusters at
bronchi/bronchiole branching points.
6. Lymphocytes- found in mucosa of bronchi, where they form germinal centers.
D. Glands
1. Mucous glands- secrete mucin in response to vagal stimulation. NOT found past
bronchi.
2. Serous glands- secrete glycoproteins, neutral and acidic polysaccharides, and
bacteriosidic proteins (e.g. lysozyme, lactoferrin, IgA). NOT found past bronchi.
NOTE: You will not have to recognize APUD, brush cells, and in all likelihood not the glandular tissue
on a typical slide during an exam. They are mentioned to give you a complete picture as to the function
of the conducting airways.
II. Respiratory Zone
A. Function- gas exchange. No need for mucus glands or big cartilage support.
B. Anatomy
1. Respiratory bronchioles- occasional alveoli open directly into the
bronchiolar lumen. More typically, the respiratory bronchiole branches into
alveolar duct.
2. Alveolar duct- elongate airways with almost no walls, except for scatter
rings of smooth muscle and the openings of alveoli.
3. Alveolar sac- spaces into which clusters of alveoli open
4. Alveoli
5. Alveolar septa- walls of tissue found between adjacent alveoli. They consist
of 2 thin epithelial layers (of 2 alveoli) which surround capillaries,
fibroblasts, elastic/collagen fibers, and the macrophages of the interstitium.
-blood-air barrier: the thinnest possible alveolar septa for gas exchange,
has 4 layers
surfactant
type I pneumocyte
basal lamina- single fused lamina of pneumocyte and capillary
endothelium
capillary endothelial cell.
C. Cell Types
1. Clara cells- these are the predominant cells in the respiratory bronchioles,
forming the epithelial lining of these airways. See above.
2. Smooth muscle- cords of smooth muscle are found in the non-respiratory
portions of the respiratory bronchioles (i.e. those portions that serve a
structural function). Clara cells still line the lumen here.
3. Type I pneumocyte- extremely thin squamous cells that line most of the
alveolar surface. Tight junctions between these and neighboring cells.
4. Type II pneumocyte- secretory cells, produce surfactant that prevents
alveolar collapse (this is a different agent than the one the Clara cells
secrete). These cells bulge into the alveolar lumen. They have apical
granules resolved on TEM or oil that are referred to as lamellar bodies.
5. Endothelial cells- non-fenestrated, squamous cells that line the alveolar
capillaries. Easily mistaken for type I pneumocytes.
6. Dust cells (aka macrophages)- you’ve seen these before. They go out into
the lumen to degrade surfactant, dust particles, and bacteria that happen to
enter the alveoli
7. Fibroblasts- found in the connective tissue septa. Produce collagen and
elastic fibers.
Segment
Trachea
Bronchi
Bronchioles
Large bronchiole
Small bronchiole
Terminal bronchiole
Support
Glands
CONDUCTING ZONE
C-ring hyaline cartilage
YES
Major Cell Type
Cartilage plates
Smooth muscle,
collagen, reticular fibers
-Pseudostratified ciliated epithelium
-Goblet cells
-Same as trachea
-Pseudostratified ciliated transition to
Simple columnar/cuboidal, ciliated
YES
NO
Smooth muscle,
NO
collagen, reticular fibers
RESPIRATORY ZONE
-Simple cuboidal ciliated
-Clara cells (nonciliated)
Respiratory bronchiole
Smooth muscle
NO
-Clara cells dominate,
-non-ciliated, cuboidal epithelium
RESPIRATORY SYSTEM QUESTIONS:
1. Which of the following is a correct pairing of the structure at the pointer and its
secretory product?
a. mucous cells: mucins
b. serous demilune: non-glycosylated proteins, bacteriostatic proteins
c. goblet cell: mucus
d. neuroepithelial cells: serotonin and substance P
2. What is the function of the cell type at the pointer?
a. secretes surface-active agent
b. structural support
c. gas exchange
d. secretes surfactant
3. The lumen at the pointer
a. requires cartilage to maintain its patency
b. is lined by stratified squamous epithelium
c. contains areas where gas exchange occurs
d. is lined by mucus glands but not serous glands
4. The segment of the respiratory system shown at the pointer
a. contains c-shaped cartilage rings
b. contains Clara cells
c. contains goblet cells but not serous glands
d. contains both goblet cells and serous glands
RESPIRATORY SYSTEM QUESTIONS & ANSWERS:
1. Which of the following is a correct pairing of the structure at the pointer and its
secretory product? (pointer on serous demilune in trachea)
a. mucous cells: mucins
*b. serous demilune: non-glycosylated proteins, bacteriostatic proteins
c. goblet cell: mucus
d. neuroepithelial cells: serotonin and substance P
2. What is the function of the cell type at the pointer? (pointer on type II pneumocyte)
a. secretes surface-active agent
b. structural support
c. gas exchange
*d. secretes surfactant
(refers to Clara cell)
(refers to smooth muscle cell)
(refers to type I pneumocyte)
(type II pneumocyte)
3. The lumen at the pointer (pointer in respiratory bronchiole)
a. requires cartilage to maintain its patency (there is no cartilage in the bronchioles)
b. is lined by stratified squamous epithelium (resp. bronchioles lined by cuboidal
epithelium)
*c. contains areas where gas exchange occurs (alveolar ducts, and thus alveoli, come off
of respiratory bronchioles)
d. is lined by mucus glands but not serous glands (neither mucus nor serous glands are
found beyond the bronchi)
4. The segment of the respiratory system shown at the pointer (pointer on bronchiole,
which lacks cartilage, glands and alveoli)
a. contains c-shaped cartilage rings (this would refer to the trachea)
*b. contains Clara cells
c. contains goblet cells but not serous glands (there are NO GLANDS OF ANY
KIND lining the bronchioles)
d. contains both goblet cells and serous glands
Oliver Stroeh & Jenny Platt
2/6/03
THE EYE
The eye can be divided into three layers:
1. The Outer Layer – Corneosclera (cornea + sclera)
2. The Middle Layer – Uvea (choroid + iris + ciliary body)
3. The Inner Layer – Retina (neuroretina + pigmented epithelium)
I. Corneosclera
Cornea – consists of:
• Corneal epithelium – stratified sqaumous, non-keratinized
• Bowman’s membrane – acellular
• Stroma – transparent, avascular regularly arranged collagen fibrils and
keratocytes
• Descemet’s membrane – thick basal lamina of corneal endothelium
• Corneal endothelium – single layer of flattened hexagonal cells that provides
for metabolic exchange with aqueous humor
Sclera
• white outer coat of the eye
• formed by dense, irregularly arranged connective tissue.
Limbus
• junction of cornea and sclera
• endothelium-lined channels merge to form the Canal of Schlemm
II. Uvea
Choroid
• highly vascular & pigmented connective tissue adjacent to retina
• separated from retina by Bruch’s membrane (lamina vitrea)
• absorbs light that passes through the retina, preventing reflective interference
Iris
• composed of loose connective tissue containing blood vessels, pigment, cells
& smooth muscle
• anterior layer = pigment cells (or melanocytes), whose number and disposition
determine eye color
• deeper layers = blood vessels and nerves, the sphincter and dilator pupillae
muscles, and a double layer of pigmented epithelium
Ciliary Body
• continuation of choroids which extends from the limbus to the ora serrata (the
anterior limit of the retina and choroids)
• covered by an outer non-pigmented epithelium and an inner pigmented
epithelium
• 3 groups of ciliary smooth muscles in connective tissue – 2 groups control
lens shape, 1 group facilitates drainage of aqueous humor
Ciliary Processes
• finger-like projections of the ciliary body
•
•
contain large blood vessels and long fenestrated capillaries
responsible for continuous production of aqueous humor
Pathway of aqueous humor:
- humor secreted into posterior chamber
- then passes between iris and lens to the anterior chamber
- enters the Canal of Schlemm, where the aqueous veins convey the
fluid to the veins in the sclera
III. Retina
Pigmented epithelium
• outer layer of retina
• made up of pigmented epithelial cells with microvillae
- these cells absorb light and phagocytose excessive membrane sheath
material
Neural Retina
• lies internal to the pigmented layer
• composed of several layers, moving external to internal:
1. Rods and Cones – outer and inner segments of photoreceptor cells
2. Outer Limiting Membrane – apical boundary of glial (Muller’s) cells
3. Outer Nuclear Layer – contains cell bodies (nuclei) of retinal rods &
cones
4. Outer Plexiform Layer – contains the processes of the horizontal,
amacrine and bipolar cells
5. Inner Nuclear Layer – contains the cell bodies (nuclei) of the
horizontal, amacrine, bipolar, and Muller’s cells
6. Inner Plexiform Layer – contains the processes of horizontal,
amacrine, and bipolar cells, and processes of ganglion cells that
connect to each other
7. Ganglion Cell Layer – contains cell bodies (nuclei) of ganglion cells
8. Optic Nerve Fibers – contains processes of ganglion cells that lead
from the retina to the brain; ganglion nerve cell axons exit the eye at
the optic disc where there are no photoreceptors (a blind spot)
9. Inner Limiting Membrane – composed of the basal lamina of Muller’s
cells
• macula
- oval depression in the retina that appears yellow
- contains the fovea – a single layer of cone cells; specialized for high
acuity vision
The Vitreous
• loose connective tissue which fills the center of the eye
• composed of thin, mostly randomly oriented, type II collagen
• no blood vessels or nerves in this area
• layer of phagocytes (hyalocytes) embedded around the border of the vitreous
The Lens
• bathed anteriorly by the aqueous humor and posteriorly by the vitreous
• avascular, non-innervated epithelial tissue
• a monolayer of cuboidal epithelial cells covers the anterior surface, serving as the
progenitor for the lens fibers
• the zonular fibers attach to the lens capsule (a thickened basal lamina) and are
anchored by the ciliary processes
[FIGURE 23.5 in Ross]
SSN Review Questions: The Eye
Jenny Platt & Oliver Stroeh
jrp2002
oms2002
1)
The region at the pointer is…
a. a single layer of cone cells.
b. specialized for high acuity vision.
c. devoid of photoreceptors.
d. the junction of the cornea and sclera.
2)
The structure indicated by the pointer…
a. inserts into the thickened basal lamina of the lens epithelium.
b. undergoes changes in tension with contraction/relaxation of the pupillae
muscles.
c. forms part of the suspensory ligament of the iris.
d. is a progenitor cell for lens fibers, which comprise most of the lens mass.
3)
a.
b.
c.
d.
Which of the following statements concerning the layer indicated
by the pointer is FALSE:
This layer contains cells whose function is to integrate or associate the
impulses from the other neurons
This layer is the outer nuclear layer.
This layer contains cells that serve as the supporting framework of the
retina
This layer lies adjacent to a layer containing cell processes, including
those of ganglion cells.
4) The layer indicated at the pointer:
a.
is Bruch’s membrane
b.
is an unusually thickened basal lamina
c.
is continuous with the retina
d.
is composed of a single layer of flattened hexagonal cells
5)
Which of the following correctly describes the structure at the pointer:
a. Pigment cells in this structure are responsible for eye color.
b. This structure contains the entire Canal of Schlemm
c. Neural cells can be found in this structure.
d. 3 groups of ciliary smooth muscle are found in this structure.
6)
Which of the following is TRUE:
This structure is lined by cuboidal epithelium.
Aqueous humor drains from the anterior chamber into the posterior chamber
and into this structure.
This structure is located in the limbus of the corneosclera.
Pigmented tissue in this structure absorbs light to prevent interference.
ANSWERS:
1)
2)
3)
4)
5)
6)
c. The pointer is on the optic disc of the eye (Eye Lab Web Graphic #17), a region that lacks all
neural elements except for the axons of ganglion cells and has no perceptive function (the eye’s
blind spot). Answer choices a. & b. describe the fovea. Answer choice d. describes the limbus.
a. The pointer is on a portion of a zonular fiber (Eye Lab Web Graphic #9). Answer choice a.
describes the lens capsule, the structure into which the zonular fibers do insert. Answer choice b.
is false since the ciliary muscle controls the tension on the zonules. Answer choice c. is incorrect
as the zonular fiber forms part of the suspensory ligament of the lens. Answer choice d. describes
the cuboidal epithelial cells covering the anterior surface of the lens.
b. The pointer is on the inner nuclear layer of the retina (Eye Lab Web Graphic #14). This layer
contains the cell bodies (nuclei) of the horizontal, amacrine, bipolar, and Muller’s cells. Answer
choice a. describes interneurons (horizontal and amacrine cells) and answer choice c. describes
glial cells (Muller’s cells). Answer choice d. describes the inner plexiform layer, which does
indeed lie adjacent to the inner nuclear layer.
b. The pointer is on Descemet’s membrane, an unusually thickened basal lamina of corneal
endothelium (Eye Lab Web Graphic #4). Answer a. is wrong because Bruch’s membrane lies
between the choroid and the retinal pigment epithelium. Answer c. is incorrect because
Descemet’s membrane is a part of the Cornea, the “Outer Layer” of the eye, whereas the retina is
part of the Inner Layer. Answer d. describes the corneal endothelium.
d. The pointer is on the ciliary body, which has 2 groups of smooth muscles that control lens
shape and 1 group that facilitates drainage of aqueous humor (Eye Lab Web Graphic #8). Answer
a. refers to the iris. Answer b. describes the limbus, where the cornea & sclera meet. Answer c is
incorrect because neural cells can only be found in the neural retina.
c. Pointer is on the Canal of Schlemm, which can be found in the limbus of the corneosclera (Eye
Lab Web Graphic #11). Answer a. is incorrect because the Canal of Schelemm is lined by
endothelium, which is a simple, squamous epitheium. Answer b. is incorrect because aqueous
humor flows from the posterior chamber to the anterior chamber between the iris and lens, and
then drains into the Canal of Schlemm. Answer d. is wrong because it describes the choroid,
which has highly vascular & pigmented connective tissue adjacent to the retina that absorbs light
that passes through the retina, preventing reflective interference.
The Ear
Stephanie White-Bateman
I.
Overview of the ear:
A.
Uses:
1. sound perception (auditory system)
2. balance + eye movement congruence (vestibular system)
B.
General architecture:
1. external ear:
a. pinna leads to
b. external auditory canal (outer 1/3 cartilaginous, inner 2/3 within
temporal bone)
2. middle ear:
a.
bounded by the tympanic membrane (lateral), temporal bone
(medial), eustachian tube (anterior) and mastoid process (posterior)
b.
tympanic membrane is attached to the malleus which is
attached to the incus which is attached to the stapes
3. inner ear:
a. within the petrous portion of the temporal bone, consists in a
membranous labyrinth within a bony labyrinth
b. contains three connected spaces: the vestibule, the cochlea and the
semicircular canals
II.
The auditory system:
A.
General cochlear architecture:
1. conically shaped helix: makes 2 _ turns around the
modiolus (central bony core)
2.
3 divisions: scala vestibuli, scala tympani, scala media
a. scala vestibuli and scala tympani:
1. essentially one long channel containing perilymph (continuous
at the “helicotrema” at the apex of the cochlea)
2. scala vestibuli: designated as that part leading from the oval
window to the helicotrema
3. scala tympani: designated as that part leading from the
helicotrema to the round window
c. scala media:
1. the “membranous cochlea” or “cochlear duct”
2. contains endolymph
3. triangular space (like right triangle)
a.
most acute angle attached to modiolus
b.
lateral wall contains stria vascularis, a vascularized,
secretory, stratified epithelium that secretes endolymph
c.
hypoteneuse is Reissner’s membrane, separating scala
media from scala vestibuli
d.
base consists of:
1. basilar membrane
2. Organ of Corti
B.
Organ of corti architecture:
1. hair cells:
a. epithelial cells containing stereocilia (note: there is no kinocilium in
cochlear hair cells!)
b. inner hair cells: auditory receptors
c. outer hair cells: “tune” the cochlea
2. phalangeal cells: support and surround hair cells and, by tight
junctions, seal the hair cells from the endolymph
3. tectorial membrane: attached on one end to modiolus; extends into
endolymph and attaches to the stereocilia of the inner and outer hair
cells
4. pillar cells: form the tunnel of Corti
C.
Function: Movement of the stapes at the oval window causes
vibrations to travel through the perilymph of the scala vestibuli (and
continue on the the scala tympani, where they are dissipated through the
round window). The pressure changes in the scala vestibuli are
transmitted to the adjacent scala media, and a traveling wave is initiated in
the basilar membrane. As the basilar membrane moves up and down, the
stereocilia of the hair cells are sheared back and forth because they are
also attached to the tectorial membrane which vibrates differently.
Bending of the stereocilia causes stretching of the hair cell plasma
membrane and the generation of transmembrane potential changes.
Depolarization of the hair cell causes an action potential in an afferent
nerve process lying beneath the Organ of Corti, and the electrical impulse
is transmitted to the spiral ganglion (stretched out within the modiolus),
and along the cochlear nerve (a division of CN VIII) to the brain stem.
Questions:
1. What is the significance of the structure at the pointer?
a. This epithelium is unique because it is the only epithelium in the body that is
vascularized.
b. This epithelium is unique because it is the only stratified epithelium in the body that
is secretory.
c. Both a and b.
d. Neither a nor b.
2. What is the function of the cells at the pointer?
a. Theses cells support the hair cells and seal them from the endolymph.
b. These cells contain an ATPase pump that maintains the sodium and potassium
concentrations of the endolymph.
c. Both a and b.
d. Neither a nor b.
(ans: c, a)
Azzie – aa2035
Vestibular system
Semicircular Canals
§ -extend from wall of vestibule
§ -at right angles to each other – superior, posterior, and horizontal
§ -at the end close to vestibule is the ampulla – 3 ampullae per ear
o -there is one crista ampullaris in each ampulla
§ -5 orifices into vestibule (superior and posterior canals share common cruss)
Receptor cells
§ -each hair cell – single kinocilium (true cilium) with numerous stereocilia (modified
microvilli)
§ -transducers – mechanical energy into electrical energy
§ -2 types (not distinguishable)
o -Type I hair cells – piriform shape with rounded base and thin neck;
surrounded by an afferent nerve cup with a few efferent fibers
o -Type II hair cells – cylindrical shape, with afferent and efferent nerve
endings
Cristae Ampullaris – Angular Movement
§ -oriented perpendicular to the long axis of the canal
§ -consists of receptor hair cells and supporting epithelial cells
§ -cupula is attached to the hair cells of each crista
o -projects into lumen and surrounded by endolymph
§ -Function:
o -when the head rotates the canals move along with the head.
o –the cupula moves faster than the endolymph surrounding it
o –causes bending of the stereocilia towards or away from the single
kinocilium
o –Example – if the head rotates to the left - in the left horizontal
semicircular canal the stereocilia move toward the kinocilium –
depolarizing the hair cell – increase firing rate
§ -the opposite happens in the right horizontal semicircular canal –
hyperpolarizing the hair cell – decrease firing rate
Maculae: Gravity & Linear Movement
§ -face the endolymph in the saccule and utricle of the vestibule – at right angles to
each other
§ -when standing – the macula utriculi is horizontal and the macula sacculi is vertical
§ -otolothic membrane is over each macula
o -otoliths (calcium carbonate and protein) on its outer surface
§ -Function – (similar to canals)
o –when the head is tilted the otoliths drag across the hair cells and cause the
stereocilia to move
VESTIBULAR SYSTEM QUESTIONS
1) The receptor cells in region 1 are involved in ___________ and the receptor cells in
region 2 are involved in ___________.
a) hearing; linear movement
b) angular movement; hearing
c) angular movement; linear movement
d) linear movement; angular movement
2) The receptor hair cells in this region have:
a) 1 stereocilium and multiple kinocilia
b) 1 stereocilium and 1 kinocilium
c) only stereocilia
d) only 1 kinocilium
e) multiple stereocilia and 1 kinocilium
Answers
1) C – Region 1 is a crista ampullaris of the semicircular canals
Region 2 is the macula of the utricle
2) E – this is the crista ampullaris – the cells in this region detect movement by bending
of stereocilia towards or away from a single kinocilium