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Sense Organ Human Anatomy and Physiology Complete Notes, Lecture notes of Anatomy

Babu Banarasi Das University Anatomy

Sense organ Complete sense organ notes of human anatomy and physiology

Typology: Lecture notes

2021/2022

Available from 01/05/2023

Dr_Raihan 🇮🇳

16 documents

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Sense Organs

Objectives

At the end of this lecture, student will be able to

• Describe the structural components of eye ball

• Explain the accessory structures of eye ball

• Distinguish between the structural components and the accessory structures of eye ball

• Describe the interior of the eye ball

• Explain image formation

• Explain the physiology of vision

• Distinguish the changes occurring during light and dark adaptation

• Explain the processing of visual signals in retina

• Describe the anatomy of ear

• Identify the receptor organs for equilibrium

• Describe the function of receptor organs for equilibrium

• Describe the auditory pathway

• Explain the major events in the physiology of hearing

• Describe the anatomy of olfactory receptor

• Explain the physiology of olfaction and olfactory transduction

• Describe the anatomy of taste bud and papillae

• Explain the physiology of gustation and gustatory pathway

• Describe the layers of the epidermis and the cells that compose them

• Describe various accessory structures of the skin

• Distinguish between the accessory structures and the main components of skin

• Explain the functions of skin

Content

• Eye ball

– Structural Component

– Accessory Structures

• Interior of the eye ball

• Image formation

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Download Sense Organ Human Anatomy and Physiology Complete Notes and more Lecture notes Anatomy in PDF only on Docsity!

Sense Organs

Objectives

At the end of this lecture, student will be able to

Describe the structural components of eye ball
Explain the accessory structures of eye ball
Distinguish between the structural components and the accessory structures of eye ball
Describe the interior of the eye ball
Explain image formation
Explain the physiology of vision
Distinguish the changes occurring during light and dark adaptation
Explain the processing of visual signals in retina
Describe the anatomy of ear
Identify the receptor organs for equilibrium
Describe the function of receptor organs for equilibrium
Describe the auditory pathway
Explain the major events in the physiology of hearing
Describe the anatomy of olfactory receptor
Explain the physiology of olfaction and olfactory transduction
Describe the anatomy of taste bud and papillae
Explain the physiology of gustation and gustatory pathway
Describe the layers of the epidermis and the cells that compose them
Describe various accessory structures of the skin
Distinguish between the accessory structures and the main components of skin
Explain the functions of skin

Content

Eye ball
Structural Component
Accessory Structures
Interior of the eye ball
Image formation

Physiology of vision
Light and dark adaptation
Anatomy of Ear
Auditory Pathway
Physiology of hearing
Anatomy of olfactory receptor
Physiology of olfaction and olfactory receptor
Anatomy of taste bud and papillae
Physiology of gustation and gustatory pathway
Skin
Layers of epidermis
Accessory structures
Function

THE EYE

Organ of the sense of sight
Responsible for the detection of visible light (400-700nm)
Location - In the orbital cavity; supplied by optic nerve

Accessory Structures of the Eye

The eyelids
Eyelashes
Eyebrows
The lacrimal apparatus
Extrinsic eye muscles

Eyelids

Upper and lower eyelids, or palpebrae
Shade the eyes during sleep
Protect eyes from excessive light and foreign objects
Spread lubricating secretions over the eyeballs
Upper eyelid more movable than the lower
Contains in its superior region the levator palpebrae superioris muscle

The Lacrimal Apparatus

A group of structures that produces and drains lacrimal fluid or tears

Lacrimal glands – supplied by parasympathetic fibers, facial (VII) nerves - Lacrimal fluid - a watery solution has salts, some mucus, lysozyme, a protective bactericidal enzyme - Lacrimation - a protective mechanism
The tears dilute and wash away the irritating substance - Crying - Excessive lacrimal fluid production by lacrimal glands in response to parasympathetic stimulation

Extrinsic Eye Muscles

Extend from the walls of the bony orbit to the sclera (white) of the eye
Surrounded in the orbit by periorbital fat
Capable of moving the eye in almost any direction Six extrinsic eye muscles move each eye
Superior rectus
Inferior rectus
Lateral rectus
Medial rectus
Superior oblique
Inferior oblique

Extrinsic eye muscles that move the eyeballs and upper eyelid

Supplied by cranial nerves III, IV, or VI
Extrinsic eye muscles move the eyeball laterally, medially, superiorly, and inferiorly
Oblique muscles preserve rotational stability of the eyeball
Neural circuits in the brain stem and cerebellum coordinate and synchronize movements of eye

Accessory structures of the eye

Anatomy of the Eyeball

Adult eyeball - about 2.5 cm in diameter
Only anterior one-sixth exposed
Remainder protected by the orbit

Provide nutrients to the posterior surface of the retina
Contains melanocytes, produce the pigment melanin (dark brown)
Melanin in the choroid absorbs stray light rays
Prevent reflection and scattering of light within the eyeball (b) Ciliary body
Anterior portion of the vascular tunic, the choroid becomes the ciliary body Ciliary body consists of: Ciliary processes
Protrusions or folds on the internal surface of the ciliary body
Extentions from ciliary process, zonular fibres (suspensory ligaments); attach to lens Ciliary muscle
A circular band of smooth muscle
Changes the tightness of the zonular fibers lters the shape of the lens dapt lens for near or far vision (c) Iris
Iris (= rainbow), the colored portion of the eyeball
Suspended between the cornea and the lens
Consists of melanocytes and circular (sphincter pupillae) and radial smooth muscle fibers (dilator pupillae)
Amount of melanin in the iris determines the eye color
Brown to black – large amount of melanin
Blue – low melanin
Green – moderate melanin concentration
Iris regulate the amount of light entering the eyeball through the pupil
Autonomic reflexes regulate pupil diameter in response to light levels

(3) Retina

Lines the posterior three-quarter of the eyeball

Is the beginning of the visual pathway
Optic disc – site, optic (II) nerve exits the eyeball
Central retinal artery, a branch of the ophthalmic artery, and the central retinal vein are bundled with optic disc Transverse section of posterior eyeball at optic disc

Retina consists of a pigmented layer and a neural layer Pigmented layer Neural (sensory) layer

Sheet of melanin-containing epithelial cells
Located between the choroid and the neural part of the retina
Melanin - also helps to absorb stray light rays
- Multilayered outgrowth of the brain
- Processes visual data extensively before sending nerve impulses into axons that form the optic nerve

Three distinct layers of retinal neurons

The photoreceptor layer
The bipolar cell layer
The ganglion cell layer

Lens

Behind the pupil and iris, within the cavity of the eyeball
In the cells of the lens, proteins called crystallins, arranged like the layers of an onion
Make up the refractive media of the lens
Transparent and lacks blood vessels
Enclosed by a clear connective tissue capsule
Held in position by encircling zonular fibers, which attach to the ciliary processes
Lens helps focus images on the retina to facilitate clear vision Anatomy of the eyeball

Interior of the Eyeball

Lens divides the interior of the eyeball into two cavities: Anterior cavity and Vitreous chamber

1. Anterior cavity- space anterior to the lens Consists of two chambers

Anterior chamber – between the cornea and the iris

Posterior chamber - behind iris and in front of zonular fibers and lens
Both chambers of the anterior cavity are filled with aqueous humor
Transparent watery fluid that nourishes the lens and cornea
Completely replaced about every 90minutes 2. Vitreous chamber
Larger posterior cavity of the eyeball
Lies between the lens and the retina Vitreous body - a transparent jellylike substance
Holds the retina flush against the choroid
Gives the retina an even surface for the reception of clear images
Contains phagocytic cells, remove debris
Keep the eye clear for unobstructed vision Intraocular pressure - pressure in the eye
Produced mainly by aqueous humor and partly by vitreous body
Normally it is about 16 mmHg
Maintains the shape of the eyeball
Prevents it from collapsing Interior of the Eyeball

Physiology of Vision

Photoreceptors and Photo pigments

Rods and cones have different appearance of the outer segment
Rods – cylindrical/ rod-shaped, plasma membrane (PM) form discs
Cones – tapered/ cone-shaped, PM folded back and forth
Photo pigments, integral proteins in the plasma membrane of the outer segment
Inner segment - contains the cell nucleus, Golgi complex, and many mitochondria Structure of rod and cone photoreceptors
Inner segments contain the metabolic machinery for synthesis of photo pigments and production of ATP
Transduction of light energy into a receptor potential occurs in the outer segments of rods and cones

Photo pigment

A colored protein, undergoes structural changes when it absorbs light, in the outer segment of a photoreceptor
Light absorption initiates production of a receptor potential
Photo pigment in rods – rhodopsin; in cones – 3 types
Photo pigments associated with vision contain two parts:
A glycoprotein, opsin
A derivative of vitamin A, retinal
Retinal - light-absorbing part of all visual photo pigments
In humans, 4 different opsins; 3 in cones; 1 in rods The cyclical bleaching and regeneration of photopigment
Blue arrows indicate bleaching steps
Black arrows indicate regeneration steps

Light and Dark Adaptation

Light adaptation— when emerging from a dark surrounding to sunshine

Visual system adjusts in seconds to the brighter environment by decreasing its sensitivity
As the light level increases, more and more photo pigment bleached

Axon collaterals of retinal ganglion cells extend to the midbrain and hypothalamus
Everything that can be seen by one eye - Eye’s visual field
We have binocular vision due to the large region where the visual fields of the two eyes overlap—the binocular visual field Visual field of each eye is divided into two regions: a) The nasal or central half b) The temporal or peripheral half
Light rays from an object in the nasal half of the visual field fall on the temporal half of the retina, and vice versa
Visual information from the right half of each visual field is conveyed to the left side of the brain, and vice versa Transverse section through eyeballs and brain

The visual pathway

The Ear

Organ of hearing
Supplied by the 8th cranial nerve, stimulated by vibrations caused by sound waves
Entire structure encased within the petrous portion of temporal lobe, except pinna

Anatomy of the ear

Ear is divided into three main regions

1. External (Outer) Ear - Auricle (Pinna) - Eardrum - External auditory canal 2. Middle Ear - Auditory ossicles - Auditory (eustachian) tube 3. Internal (inner) ear - Cochlea - Vestibular apparatus - Semicircular ducts

Utricle
Saccule

Contains two small membrane-covered openings:
The oval window
The round window Auditory ossicles
Three smallest bones in the body
Extending across the middle ear and attached to it by ligaments
Connected by synovial joints The bones, named for their shapes
The malleus (Hammer)
Incus (Anvil)
Stapes (Stirrup)
Incus, the middle bone in the series, articulates with the head of the stapes
Base or footplate of the stapes fits into the oval window
Round window
Opening below the oval window
Enclosed by a membrane, the secondary tympanic membrane Two tiny skeletal muscles attach to the ossicles Tensor tympani muscle Stapedius muscle
Supplied by the trigeminal (V) nerve • Supplied by the facial (VII) nerve
Limits movement • Smallest skeletal muscle in the human body
Increases tension on the eardrum • Protects the oval window
Prevent damage to the inner ear from loud noises • decreases sensitivity of hearing

The Auditory ossicles

Auditory (eustachian) tube

Opening in the anterior wall of the middle ear
Consists of both bone and elastic cartilage
Connects the middle ear with the nasopharynx
Normally closed at its medial (pharyngeal) end
During swallowing and yawning, it opens
Allows air to enter or leave the middle ear until the pressure in the middle ear equals the atmospheric pressure

Internal (inner) ear

Also called the labyrinth
Because of its complicated series of canals Consists of two main divisions:
An outer bony labyrinth encloses an inner membranous labyrinth

Bony labryinth - A series of cavities in the petrous portion of the temporal bone Divided into three areas: (1) The semicircular canals, contain receptors for equilibrium (2) The vestibule, contain receptors for equilibrium (3) The cochlea, contains receptors for hearing

Bony labyrinth, lined with periosteum and contains perilymph
Epithelial membranous labyrinth contains endolymph
Potassium ions in endolymph helps in generation of auditory signals

Sense Organ Human Anatomy and Physiology Complete Notes, Lecture notes of Anatomy

Related documents

Partial preview of the text

Download Sense Organ Human Anatomy and Physiology Complete Notes and more Lecture notes Anatomy in PDF only on Docsity!

Sense Organs

Objectives

Content

THE EYE

Accessory Structures of the Eye

Eyelids

The Lacrimal Apparatus

Extrinsic Eye Muscles

Accessory structures of the eye

Anatomy of the Eyeball

Lens

Interior of the Eyeball

Light and Dark Adaptation

The Ear

Anatomy of the ear

Internal (inner) ear