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Questions and Answers
Which layer of the skin is primarily responsible for providing a sensory function?
What is one of the primary roles of the hypodermis?
Which component in the integument is responsible for lubrication of both hair and skin?
What adaptation allows the nose (rhinarium) to protect against UV light?
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How does the structure of the footpads differ between dogs and cats?
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What is the primary purpose of the arrector pili muscle?
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Which structure in the claw is responsible for extending the claw?
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What is the major function of melanin related to the skin?
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What is a primary function of the integument?
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Which layer of the epidermis is responsible for synthesizing keratin?
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What is the role of melanocytes in the skin?
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Which of the following layers of the eye is responsible for maintaining its shape?
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How does the integument contribute to homeostasis?
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What is the function of the sebaceous glands in the integument?
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What type of epithelium comprises the epidermis?
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What is the primary purpose of Vitamin D3 synthesis in the integument?
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What role does the ciliary muscle play concerning the lens?
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What happens at the optic chiasma?
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Which part of the ear separates the external ear from the middle ear?
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What is the primary function of the cochlea?
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What is the significance of the tapetum lucidum in the retina?
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Which structure of the ear is involved in maintaining balance?
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How do predators differ in visual perception compared to prey?
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What are the auditory ossicles responsible for?
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What is the primary function of the choroid layer in the eye?
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Which part of the eye is responsible for nighttime vision?
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What role does the ciliary body play in vision?
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Why does the pupil appear black?
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What causes the 'blind spot' in the retina?
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How do the suspensory ligaments contribute to vision?
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What is the function of bipolar neurons in the retina?
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What is the main purpose of the tapetum lucidum?
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What are the two sac-like structures contained within the vestibule?
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Which part of the inner ear is responsible for detecting sound?
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Which cranial nerve carries sensory information about balance from the vestibule?
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What type of receptors detect pain stimuli in the skin?
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What is the function of the vomeronasal organ (Jacobson’s organ)?
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How do chemicals stimulate taste buds?
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What characteristic of dogs enhances their olfactory capability?
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Which type of sensory receptors in the skin is responsible for detecting temperature changes?
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Study Notes
Integument
- Outer covering of the body.
- Consists of the skin, hair, footpads, and claws
Skin
- The external surface of the body.
- Acts as a barrier against the external environment.
- Consists of three layers:
- Epidermis: Outermost layer
- Dermis: Middle layer
- Hypodermis: Deepest layer
Functions of the Skin
- Protection: Protects the body from the external environment and pathogens.
- Sensory: Detects touch, temperature, and pain.
- Secretion/Excretion: Secretes sweat and sebaceous fluids.
- Production: Produces Vitamin D.
- Storage: Hypodermis stores fat.
- Pigmentation: Produces melanin, which protects the skin from UV light.
Footpads
- Epidermis is thickened and hairless.
- Adipose tissue in the dermis forms the digital cushion.
- Dogs have conical papillae, giving a rough feel.
- Cats have a smooth epithelial surface.
Nose/Rhinarium
- Hairless and contains keratin for toughness.
- Heavily pigmented for UV protection.
Claws
- Composed of:
- Unguicular Crest: Claw covering the unguicular process.
- Unguicular Process: Claw base.
- Extensor Tendons: Extend the claw.
- Middle Phalanx: Middle bone of the digit.
- Tendon of Deep Digital Flexor: Flexes the middle phalanx.
- Flexor Tubercle: A small bump on the middle phalanx.
- Distal Phalanx: Tip of the claw.
- Digital Pad: Pad below the claw.
Hair
- Composed of:
- Hair Follicle: Structure that holds the hair root.
- Hair Bulb: Base of the hair follicle.
- Hair Root: Anchors hair to the skin.
- Hair Shaft: Visible portion of the hair.
- Arrector Pili Muscle: Contracts to raise hair.
- Pore of Sweat Gland Duct: Opening of the sweat gland.
- Sebaceous Gland: Secretes oily substance that lubricates hair and skin.
- Eccrine Sweat Gland: Secretes sweat.
- Pacinian Corpuscle: Detects pressure and vibrations.
Dermis
- Middle layer of the skin.
- Composed of dense connective tissue that is vascular.
- Contains nerve fibers, nerve endings, and elastic fibers.
- Also contains hair follicles, and sweat and sebaceous glands.
Hypodermis
- Deepest layer of the skin.
- Subcutaneous layer composed of loose connective tissue and fat.
Functions of the Integument
- Protection: Protects the body from the external environment and prevents entry from pathogens.
-
Maintenance of Homeostasis
- Conserving water
- Maintaining body temperature.
- Excretion: Excretes materials through the sebaceous glands and sweat glands.
- Synthesis of Vitamin D: Synthesizes Vitamin D3 from UV light. Liver converts Vitamin D3 into a compound used to synthesize calcitriol. Calcitriol regulates absorption of calcium and phosphorus from the intestines.
- Storage: Stores fat for energy reserves.
- Sensation: Sensory receptors in the dermis detect chemical, mechanical, and thermal stimuli, protecting the animal from injury and damage.
- Pigmentation: Melanocytes (junction of dermis and epidermis) produce melanin, which protects the animal from UV light.
Epidermis
- Superficial, avascular layer of the skin.
Stratified Squamous Epithelium
- The epidermis is composed of stratified squamous epithelium.
- Consists of five layers:
- Stratum Corneum: Outermost layer of keratinized cells that are constantly being sloughed off. Keratinization is complete in this layer.
- Stratum Lucidum: Thin layer of cells that have lost their nuclei. Only present in thick skin (e.g. palms of hands and soles of the feet).
- Stratum Granulosum: Cells contain granules of keratohyalin. Responsible for synthesizing keratin.
- Stratum Germinativum: Deepest layer of the epidermis (also known as the basal layer). Stem cells continuously divide to produce new epidermal cells.
- Stratum Spinosum: Thick layer of cells connected by desmosomes. Contains keratinocytes.
Special Senses
Eye
- Specialized sense organ that detects light.
- Consists of three layers:
- Sclera: Tough outer layer that maintains the shape of the eye.
- Uvea: Middle layer (also known as the vascular layer). Consists of the choroid, ciliary body, and iris.
- Retina: Innermost layer. Contains photoreceptor cells that convert light into nerve impulses.
Eye Position
- Depends on the animal's environment.
- Poor blood supply but well supplied with nerve fibers.
- Cornea is the first part of the eye to be hit by light, focusing light onto the retina.
Choroid
- Darkly pigmented, vascular layer of the eye that lies adjacent to the retina.
- Contains blood vessels that supply internal structures and prevent light from escaping.
Tapetum Lucidum
- Triangular area of yellow-green iridescent light-reflecting cells in the choroid.
- Reflects light back to the photoreceptor cells, improving night vision (hence "eye shine" in animals when headlights are pointed at them).
Ciliary Body
- Smooth muscle, a continuation of the ciliary body, that controls the thickness and shape of the lens by adjusting tension on the suspensory ligaments.
Suspensory Ligaments
- Radial and circular muscle fibers that surround the lens.
- Support the lens and help to focus light.
Iris
- Colored part of the eye that controls the amount of light entering the eye by regulating the size of the pupil.
- The pupil appears black because the choroid is opaque and darker than the iris.
- Pigmented cells in the iris give the eye its color.
- Nerve supply is via the oculomotor nerve.
Retina
- Innermost layer of the eye containing photoreceptor cells that detect light.
- Closest to the choroid, has an augmented layer that prevents light leaking into the eyeball.
Photoreceptor Cells
- Responsible for detecting light.
- Rods: Detect black and white, used for night vision (responsible for 95% of vision).
- Cones: Detect color, used for daytime vision (responsible for 5% of vision).
Bipolar Neurons
- Transmit information from the rods and cones to the next layer, the ganglion cells.
Ganglion Cells
- Nerve cells in the retina whose axons travel along the retina to the optic disc.
- The optic disc marks the location where the optic nerve leaves the eye and contains no rods and cones, creating a "blind spot".
Formation of an Image
- Four-step process:
-
Light Rays: Pass through:
- Cornea and pupil: Cornea bends the light rays, the pupil controls the amount of light entering the eye.
- Lens: Focuses the light rays onto the retina. Curvature of the lens is adjusted by the ciliary muscle.
- Retina: Photoreceptor cells on the retina detect the light rays. Some light is reflected back by the tapetum lucidum to stimulate more photoreceptor cells.
- Nerve Impulses: Light rays are converted into nerve impulses that travel along the optic nerve to the brain.
- Optic Chiasma: Some of the nerve impulses cross to the opposite side of the brain at the optic chiasma, so that each cerebral hemisphere receives information from both eyes.
- Visual Cortex: Nerve signals are carried to the visual cortex of the cerebral hemispheres where they are interpreted as an image. The image formed on the retina is an inverted and smaller image of the original object, but the brain automatically inverts it.
- Predators: Have a narrow field of view and a wide area of binocular vision.
- Prey: Have a wide field of view and a narrow area of binocular vision.
-
Light Rays: Pass through:
Ear
- Organ of hearing and balance.
- Divided into three parts:
- External Ear: Consists of the pinna/auricle, the external acoustic meatus (EAM), and ceruminous glands.
- Middle Ear: Consists of the tympanic membrane, the tympanic cavity, and the auditory ossicles.
- Inner Ear: Consists of the cochlea, the vestibule, and the semicircular canals.
External Ear
- Consists of:
- Pinna/Auricle: External part of the ear. Directs soundwaves towards the EAM.
- External Acoustic Meatus (EAM): Canal leading to the eardrum.
- Ceruminous Glands: Secrete earwax which traps foreign materials.
Middle Ear
- Consists of:
- Tympanic Membrane: Eardrum, separates the external ear from the middle ear. Vibrates in response to soundwaves and transmits these vibrations to the auditory ossicles.
- Tympanic Cavity: Air-filled space behind the eardrum that contains the auditory ossicles.
- Auditory Ossicles: Three small bones (malleus, incus, and stapes) in the tympanic cavity, connected by synovial joints to transfer vibrations from the eardrum to the inner ear.
Inner Ear
- Lies within the petrous temporal bone.
- Contains the cochlea, the vestibule, and the semicircular canals.
Cochlea
- Snail-shaped structure that is filled with a fluid called endolymph.
Vestibule
- Structure containing two sac-like structures:
- Utricle: Central part of the vestibule.
- Saccule: Smaller, spherical sac lying beneath the utricle.
Semicircular Canals
- Three canals filled with a fluid called endolymph.
- Connected to the vestibule by the ampulla.
- Ampullae contain sense organs – “crista” – that sense motion.
Membranous Labyrinth
- Network of interconnected tubes filled with endolymph.
- Contains all parts of the inner ear: the cochlea, the vestibule, and the semicircular canals.
Vestibulocochlear Nerve (Auditory Nerve)
- Cranial nerve that carries information from the inner ear to the brain.
- Made up of two branches:
- Cochlear branch: Carries sensory information about sound from the cochlea.
- Vestibular branch: Carries sensory information about balance from the vestibule and semicircular canals.
Taste (Gustation)
- Taste buds are the primary organs for flavor.
- Located on the tongue, soft palate, and epiglottis.
- Chemicals dissolve in saliva and stimulate the taste buds.
- Sensory signals travel via the glossopharyngeal nerves and the vagus nerve.
Touch
- Touch receptors are found in the skin.
- There are different types of touch receptors, each designed to detect a specific type of stimulation:
- Pain receptors: Free nerve endings in the epidermis detect pain stimuli.
- Heat/cold receptors: Encapsulated in the dermis, they are bulbous corpuscles that detect heat (bulbs are “hot”) and cold.
- Pressure receptors: Lamellar corpuscles that detect pressure.
- Touch receptors: Meniscoid corpuscles, found in the dermis and epidermis.
Smell (Olfaction)
- Smell is detected by numerous olfactory nerves that pass through tiny holes in the ethmoid bone.
- These nerves are directly connected to the olfactory lobe in the brain.
- Molecules dissolved in mucus lining the nasal passage stimulate the olfactory nerve endings.
Vomeronasal Organ (Jacobson’s Organ)
- Also known as Jacobson's organ.
- Associated with the Flehmen response in dogs.
- Involved in detecting pheromones.
Dogs
- Dogs have tightly coiled nasal conchae, which increases the surface area of the nasal cavity.
- This heightens their sense of smell.
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Description
Test your knowledge on the integumentary system, focusing on the structure and functions of the skin. This quiz covers various components like the outer layers, footpads, and specialized features of the skin in mammals. Gain a better understanding of how the skin protects and interacts with the environment.
