Lecture 14: The Respiratory System

Lecture 14: The Respiratory System

Structure of Respiratory System

• Two subdivisions: upper and lower respiratory system
• Upper respiratory system: nose, nasal cavity, pharynx
• Lower respiratory system: larynx, trachea, bronchial tree, lungs

The Nose

• Composed of nasal bones, cartilage, and connective and adipose tissue
• Nostrils also known as nares

The Nasal Cavity

• Roles: warm and moisten incoming air, olfaction (sense of smell), and speech (resonance chamber)
• Divided in two by nasal septum
• Anterior region: hyaline cartilage
• Posterior region: different bones
• Vestibule: anterior region lined with skin with coarse hair (stratified squamous epithelia)
• Respiratory region: posterior region lined with mucosa (ciliated pseudostratified epithelial cells)

The Nasal Cavity

• Contains nasal conchae and mucus membrane-lined meatuses (grooves)
• Increase surface area and cause incoming air to swirl
• Warms and moistens incoming air
• Lacrimal duct drains into the cavity below the inferior nasal conchae

The Olfactory Area

• Located in the roof of the nasal cavity
• Involved in the sense of smell
• Contains neurons that act as olfactory receptors

The Paranasal Sinuses

• Two each in the following bones: frontal, sphenoid, ethmoid, and maxillae
• Sinusitis: inflammation of mucous membranes of the sinuses

The Pharynx

• Nasopharynx: located posterior to the nasal cavity/internal nares
  • Contains the openings to the nasal apertures and the auditory/eustachian tubes
  • Contains the pharyngeal tonsil (adenoid)
• Oropharynx: located posterior to the oral cavity (between soft palate and top of epiglottis)
  • Lined with stratified squamous epithelial cells
  • Passageway for air and food
  • Contains the palatine and lingual tonsils
• Laryngopharynx: located between the epiglottis and the opening of the larynx
  • Lined with stratified squamous epithelial cells
  • Passageway for air and food

The Larynx

• Passageway for air composed of 9 pieces of cartilage (all are composed of hyaline cartilage except the epiglottis)
  • Thyroid cartilage: anterior wall, forms Adam's apple
  • Cricoid cartilage: forms complete ring
  • Epiglottis: covers glottis during swallowing, composed of elastic cartilage
  • Arytenoid cartilages (2): attached to the vocal cords
  • Two cuneiform and two corniculate cartilages

The Vocal Cords

• Two pairs of folds in the mucosa
  • Vestibular folds (false vocal cords)
  • True vocal cords (produce sound)
  • The true vocal cords are located in an opening known as the glottis (covered by epiglottis during swallowing)

The Trachea

• Connects larynx to the main bronchi
• Located anterior to the esophagus
• Consists of 20 C-shaped pieces of hyaline cartilage (opening faces the esophagus)

The Bronchial Tree

• Leads from the main bronchi to the alveolar ducts
• In the lower bronchi, cartilage is replaced by smooth muscle and elastic fibers
• Epithelial cells in the upper bronchi are ciliated and pseudostratified
• Epithelial cells in the lower bronchi are non-ciliated and squamous

The Lungs

• Right and left lungs are separated by the mediastinum (containing the heart)
  • Right lung: three lobes (superior, middle, and inferior lobes)
  • Left lung: two lobes (superior and inferior lobes), cardiac notch where heart is

The Pleural Membrane

• Each lung is enclosed by its own double-layered pleural membrane
  • Visceral pleural membrane: covers surface of the lung
  • Parietal pleural membrane: attached to inner thoracic wall, diaphragm, and mediastinum
• Pleural cavity: contains pleural fluid which reduces friction and holds lungs to the walls of the thoracic cavity

The Conduction Zone

• The region from the nasal cavity to the terminal bronchioles is known as the conduction zone
• Conducts air from the environment to the respiratory zone

The Respiratory Zone

• The region from the respiratory bronchioles to the alveoli is known as the respiratory zone
• Responsible for the exchange of gases (O2/CO2) between the blood and the lungs

The Respiratory Membrane

• Consists of the walls of the alveoli and the blood vessels
• Walls of blood vessels are composed of simple squamous epithelial cells and a basement membrane
• Walls of alveoli are composed of type I and type II alveolar cells and a basement membrane

Ventilation/Breathing

• Requires two separate events: inspiration/inhalation and expiration/exhalation
• Inspiration/inhalation: intake of air into the lungs
• Expiration/exhalation: movement of air out of the lungs

Lecture 15: The Digestive System

The Mucosa

• Composed of three distinct layers: epithelium, lamina propria, and muscularis mucosae
• Epithelium: functions include protection, secretion, and absorption
• Lamina propria: connective tissue with blood and lymph vessels and MALT
• Muscularis mucosae: thin layer of muscle (makes folds in the lumen)

The Submucosa

• A layer of areolar connective tissue that serves to bind mucosa to muscularis
• Contains blood, lymphatic vessels, and nerves plexus

The Muscularis

• Two layers of smooth muscle: inner circular and outer longitudinal
• Myenteric nerve complex between layers
• Contractions cause motility (mixing and movement)

The Serosa

• Also known as the visceral peritoneum or adventitia
• Serves as the outermost covering of the organs (the esophagus lacks a serosa)

Oral Cavity

• Includes: lips, cheeks, palate, and tongue
• Palate: hard palate (2 maxillae and 2 palatine bones) and soft palate (posterior to hard palate)
• Tongue: attached to hyoid bone, skeletal muscle, projections of the mucosa (papillae = taste buds)

Salivary Glands

• Three pairs: parotid, submandibular, and sublingual
• Saliva: 99.5% water, 0.5% solutes (e.g., enzymes)

Dentition/Teeth

• Located in maxillae and mandible
• Child dentition: primary dentition/deciduous (baby) teeth
• Adult dentition: secondary dentition/permanent teeth

Tooth Structures

• Crown: above the gum
• Root: dentin and cementum overlay
• Neck: enamel and cementum boundary (gums)

Oropharynx and Laryngopharynx

• Contains only muscularis externa (skeletal muscles) and stratified squamous cells

Esophagus

• Located posterior to the trachea
• Passes through the diaphragm to the abdominal cavity
• All four histological layers in GI tract from this point on
• Muscularis externa: upper 1/3 = skeletal muscles, middle layer = smooth and skeletal, lower layer = smooth muscle

Stomach

• Four main regions: cardia, fundus, body, and pyloric region
• Converts food into chyme (food + gastric juice)
• Invaginations form gastric glands
• Rugae: folds in the mucosa and submucosa (allows expansion without tearing)

Small Intestine

• Pyloric sphincter to ileocaecal valve
• Made up of three layers
• Plicae circulares (circular folds): ridges in the mucosa and submucosa (cause chyme to spiral as it passes through)
• Villi: finger-like projections of mucosa (contain blood and lymph vessels), lymph vessels absorb dietary fats
• Microvilli: projections of the plasma membrane of absorptive cells (form what is known as the brush border)

Accessory Organs

• Pancreas: composed of head, body, and tail
• Liver: four lobes (right, left, quadrate, caudate)
• Gall bladder: muscular sac on the surface of the liver

Lecture 16: The Urinary System

The Kidneys

• Located retroperitoneally
• Right kidney lower than left kidney
• Supported and protected by three layers of connective tissue
• Renal cortex is the outermost surface
• Renal medulla divided into renal pyramids, renal columns, and the renal corpuscle

The Renal Corpuscle

• Located in the cortex
• Site of blood filtration
• ComposedHere are the study notes organized by topic:
• Male Reproductive System*

Bulbourethral Gland (Cowper glands)

• Located below prostate in urogenital diaphragm
• Secrete thick alkaline mucus to neutralize acidic urine and lubricate
• Secrete 5% of semen

Spermatogenesis

• Differentiation of spermatids = spermiogenesis
• Involves developing flagella, acrosome, and losing most of cytoplasm

Spermatozoa

• Head: contains nucleus with 23 chromosomes, acrosome with digestive enzymes
• Body (midpiece): contains large numbers of mitochondria to produce ATP for movement
• Tail (flagellum): propels sperm, made of microtubules

Semen

• Contains sperm, testicular fluid, and accessory gland secretions
• 2-5 ml released at ejaculation, pH 7.2-7.6
• Provides nutrients, protection, and transportation medium
• Female Reproductive System*

Ovaries (gonads)

• Located in pelvic cavity on lateral sides of uterus
• Histology: four layers, including superficial/germinal epithelia, tunica albuginea, ovarian cortex, and ovarian medulla

Uterine/Fallopian Tubes

• Three sections: infundibulum, ampulla, and isthmus
• Histology: three layers, including mucosa, muscularis externa, and serosa

Uterus

• Hollow organ composed of fundus, body, and cervix
• Histology: three layers, including perimetrium, myometrium, and endometrium
• Endometrium: two layers, including stratum functionalis and stratum basalis
• Oogenesis*
• 1º oocytes begin meiosis I before birth, arrested in prophase I
• LH stimulates completion of meiosis I, and 2º oocyte is formed
• Ovarian Follicles and Follicular Development*
• Primordial follicles: 1º oocyte surrounded by single layer of flat follicular cells
• Primary follicles: single layer becomes cuboidal, granulosa cells proliferate and secrete zona pellucida
• Secondary follicles: follicular cells secrete fluid, estrogen secretion begins
• Vesicular follicles: fluid-filled spaces unite to form antrum, granulosa cells surround oocyte
• Corpus luteum: follicle that remains after ovulation, produces estrogen and progesterone
• Mammary Glands*
• One per breast, modified sweat glands that produce milk
• Hormones*
• Steroids: synthesized from cholesterol, include testosterone, estrogen, and vitamin D
• Hormones derived from amino acids: include thyroxine, epinephrine, and norepinephrine
• Peptide or protein hormones: include oxytocin, antidiuretic hormone, and insulin
• Pituitary Gland*
• Suspended from hypothalamus, divided into anterior and posterior lobes
• Anterior pituitary gland: composed of epithelial tissue, regulates growth and metabolism
• Posterior pituitary gland: composed of nervous tissue, stores and secretes hormones produced by hypothalamus
• Other Endocrine Glands*
• Thyroid gland: produces thyroxine, regulates cellular metabolism
• Adrenal glands: produce cortisol, aldosterone, and epinephrine
• Pancreas: produces glucagon, insulin, and somatostatin
• Hypothalamus: produces hormones that regulate anterior pituitary gland
• Nervous System*
• Central Nervous System (CNS): brain and spinal cord
• Peripheral Nervous System (PNS): nerves that connect CNS to rest of body
• Neurons: cell body, dendrites, axon, and axon terminal
• Myelinated neurons: wrapped in layers of cell membranes from Schwann cells or oligodendrocytes
• Brain*
• Cerebrum: divided into two hemispheres, with gyri and sulci
• Cerebral cortex: 2-4 mm thick, divided into functional areas
• Cerebral white matter: tracts of myelinated neurons, including association, commissural, and projection tracts
• Brain Regions*
• Forebrain: includes cerebrum, diencephalon, and telencephalon
• Diencephalon: includes thalamus, hypothalamus, and epithalamus
• Cerebral basal nuclei: paired masses of gray matter, control skeletal muscle movement### Brain Stem
• The brain stem consists of the midbrain, pons, and medulla oblongata.
• The midbrain connects the pons and diencephalon, and contains the cerebral aqueduct.
• The anterior part of the midbrain contains the cerebral peduncle, which is a projection tract.
• The posterior part of the midbrain contains four nuclei/colliculi, known as the corpora quadrigemina.

Midbrain

• The midbrain contains two superior colliculi, which are responsible for visual reflexes.
• The midbrain also contains two inferior colliculi, which are responsible for hearing.

Pons

• The pons is located inferior to the midbrain.
• The pons contains tracts that connect the spinal cord to the brain, and tracts that connect to and from the cerebellum.
• The pons also contains the pontine respiratory center.

Medulla (Oblongata)

• The medulla is located inferior to the pons.
• The medulla ends at the foramen magnum, which is a hole in the skull.
• The medulla contains two bulges/pyramids, which are motor tracts.
• The medulla also contains vital centers, including the cardiac, vasomotor, and respiratory centers.

Brain Stem

• The midbrain, pons, and medulla are collectively known as the brain stem.

Cerebellum

• The cerebellum is located posterior to the pons and medulla.
• The cerebellum contains folds known as folia.
• The cerebellum has a cortex, which is grey matter, and arbor vitae, which is white matter.
• The cerebellum serves to coordinate skeletal muscle contractions, and is involved in maintaining balance and posture.

Limbic System

• The limbic system is a number of nuclei located in the cerebrum and diencephalon.
• The limbic system regulates emotions, such as laughing and crying.
• The limbic system also contains areas involved in memory, which can evoke emotions.

Reticular System

• The reticular system is a number of nuclei located in the brain stem, cortex, thalamus, and hypothalamus.
• The reticular system regulates alertness and attention, and filters stimuli, only sending new or unusual signals to the brain.

Spinal Cord Structure: Overview

• The spinal cord begins at the foramen magnum, which is a hole in the skull.
• The spinal cord ends at the conus medullaris, which is at the level of L1 or L2.
• Nerves continue down the vertebral foramina as the cauda equina, which is a bundle of nerves.
• Nerves exit at the intervertebral foramina.

Spinal Cord Structure: Overview

• The spinal cord has a filum terminale, which is a connective tissue extension of the pia mater.
• The filum terminale anchors the conus medullaris to the coccyx.
• The spinal cord is the location where CSF samples are taken.

Cross-Sectional Structure

• The spinal cord has an anterior median fissure and a posterior median sulcus, which separates the cord into right and left halves.
• The central canal of the spinal cord contains cerebrospinal fluid (CSF).

Cross-Sectional Structure

• The gray matter of the spinal cord contains cell bodies and dendrites of motor neurons and interneurons.
• The gray matter is shaped like a butterfly or an H.
• The cross bar of the gray matter is the gray commissure.

Cross-Sectional Structure

• Each side of the spinal cord is divided into horns.
• The dorsal horn is sensory, the lateral horn is motor, and the ventral horn is motor.

Cross-Sectional Structure

• The white matter of the spinal cord contains the myelinated axons of ascending (sensory) and descending (motor) tracts.
• The white matter forms specific columns, including the dorsal column, lateral column, and ventral column.

Spinal Cord Functions

• The spinal cord carries sensory and motor impulses to and from the brain.
• The spinal cord produces reflexes, which are fast, predictable, and autonomic responses to changes in the environment.

Peripheral Nervous System: Cranial Nerves

• There are 12 pairs of cranial nerves.
• The brain regions associated with the cranial nerves are the cerebrum, cerebellum, and brain stem.

Peripheral Nervous System: Cranial Nerves

• Two pairs of cranial nerves are only sensory, and one pair is mainly sensory.

Peripheral Nervous System: Spinal Nerves

• There are 31 pairs of spinal nerves, which are all mixed nerves.
• The spinal nerves exit via the intervertebral foramina.
• Each spinal nerve has two points of attachment to the spinal cord.

Peripheral Nervous System: Spinal Nerves

• The dorsal root of a spinal nerve is sensory, and contains cell bodies in the dorsal root ganglia.
• The ventral root of a spinal nerve is autonomic and somatic motor, and contains cell bodies in the ventral or lateral horns.

Cross-Section of Nerve

• A nerve contains many neurons with a number of connective tissue wrappings.
• The epineurium is a wrapping around the entire nerve, the perineurium is a wrapping around fascicles, and the endoneurium is a wrapping around the axon and myelin sheath.

Peripheral Nervous System: Sensory/Afferent Division

• Receptors detect changes in the environment.
• Receptors are classified by location, including exteroceptors, interoceptors, and proprioceptors.
• Receptors are also classified by type of stimulus, including mechanoreceptors, thermoreceptors, chemoreceptors, photoreceptors, and nociceptors.

Peripheral Nervous System: Sensory/Afferent Division

• The structure of receptors (general senses only) includes free nerve endings and encapsulated nerve endings.
• Free nerve endings are terminal dendrites of unipolar sensory neurons, and are associated with pain and root hair plexus.
• Encapsulated nerve endings are terminal dendrites enclosed in connective tissue, and are associated with Meissner's and Pacinian corpuscles.

Peripheral Nervous System: Sensory/Afferent Division

• A first order neuron is a unipolar neuron attached to or associated with a receptor, and may or may not be encapsulated.
• The axon of a first order neuron travels in cranial or spinal nerves to the CNS.
• The cell bodies of first order neurons are located in sensory ganglia of cranial nerves or dorsal root ganglia of the spinal cord.

Peripheral Nervous System: Motor/Efferent Division

• The CNS sends impulses to effectors through the motor/efferent division.
• The motor/efferent division is divided into somatic and autonomic subdivisions.
• The somatic subdivision is concerned with skeletal muscles, and consists of lower motor neurons.
• The autonomic subdivision is concerned with smooth muscle, cardiac muscle, and glands, and consists of two successive multipolar neurons.

Peripheral Nervous System: Motor/Efferent Division

• The autonomic subdivision is divided into sympathetic and parasympathetic nervous systems.
• The sympathetic nervous system is involved in the "fight or flight" response, and the parasympathetic nervous system is involved in promoting relaxation and reducing stress.

Nervous System Pathways/Ascending Pathway

• The ascending pathway is a sensory pathway that involves three successive neurons from the receptor to the cortex.
• The first order neuron is a receptor neuron, the second order neuron is an interneuron in the dorsal horn, and the third order neuron is an interneuron in the thalamus.

Nervous System Pathways/Ascending Pathway

• The axons of the first and second order neurons form ascending spinal tracts, including the dorsal column tract and the spinothalamic tract.
• The dorsal column tract is involved in sensations that are precisely located, and the spinothalamic tract is involved in sensations that are more diffuse.

Nervous System Pathways/Descending Pathway

• The descending pathway is a motor pathway that involves two neurons from the brain to the effector.
• The upper motor neuron is a neuron in the CNS, and the lower motor neuron is a neuron in the PNS.

The Eyes

• The eyes have a fibrous tunic, a vascular tunic, and a nervous/sensory tunic.
• The fibrous tunic includes the sclera and cornea.
• The vascular tunic includes the choroid, ciliary body, and iris.
• The nervous/sensory tunic includes the retina.

The Eyes

• The retina has an outer pigmented layer and an inner neural layer.
• The inner neural layer has three layers: photoreceptors, bipolar cells, and ganglion cells.
• The photoreceptors are rods and cones.
• The rods are sensitive to black and white, and the cones are sensitive to color.

The Ears

• The ears have an external ear, a middle ear, and an inner ear.
• The external ear includes the auricle, external auditory canal, and tympanic membrane.
• The middle ear includes the Eustachian tube, ear ossicles, and oval window.
• The inner ear includes the bony labyrinth, membranous labyrinth, and cochlea.

The Ears

• The coch