Veterinary Medicine Study Notes: Respiratory and Digestive Systems

P3 Timetable Topics

  • C1: Respiratory - March 10

  • C2: Digestive - March 16

  • C3: Urinary - March 17

  • Reproductive - March 18 – 6 PM

  • Eye & Ear - Written Revalida - March 20 - 7 PM

  • P3 Exam - March 27

SWU Veterinary Medicine

  • Course Code: VEM 023

  • Lesson 8: Respiratory

  • Instructor: Dr. ZanthoPe Czarina B. Perez, Assistant Professor I

Nasal Cavity Overview

  • The nasal cavity is divided as follows:

    • Nasal septum: Separates the nasal cavity into left and right sides.

    • Turbinates: Three curved plates extending from the lateral walls (Dorsal, Middle, and Ventral turbinates).

Nasal Cavity Layers and Cell Types

  • Lining Epithelium (LE):

    • Pseudostratified Columnar Stereociliated Epithelium

    • Contains:

      • Olfactory Cells: Bipolar neuron chemoreceptors.

      • Sustentacular Cells: Protect olfactory cells, apically located cylindrical cells.

      • Basal Cells: Basally located cuboidal cells that protect olfactory cells.

  • Structure: Occupies the ventro-caudal 2/3rds;

    • Histological Regions:

      • Vestibular Region: Transitional area with skin (stratified squamous keratinized) and sinus hairs (vibrissae).

      • Respiratory Region: Lined with typical Respiratory Epithelium; vascularized for heat transfer and humidity.

      • Olfactory Region: Contains olfactory epithelium.

Regions of the Nasal Cavity

  1. Nasal Vestibule:

    • Small space internally to the naris lined with skin and contains hair follicles.

  2. Respiratory Region:

    • Largest part with respiratory epithelium.

  3. Olfactory Region:

    • Small at the apex, featuring olfactory epithelium.

Vestibular Region Histology

  • Composition:

    • Loose connective tissue.

    • Skin (stratified squamous keratinized epithelium).

Respiratory Region Histology

  • Mucosa: Pseudostratified Columnar Ciliated Epithelium with goblet cells.

  • Supporting Structures: Bone, Loose connective tissue (erectile tissue, with blood sinuses), and mixed glands.

Respiratory Epithelium Details

  • Composition: 5 main cell types in contact with a thick basement membrane:

    1. Ciliated Columnar Cells

    2. Goblet Cells

    3. Brush Cells

    4. Small Granule Cells

    5. Basal Cells

Olfactory Region

  • Contains:

    • Sustentacular Cells

    • Pseudostratified Columnar Stereociliated Epithelium

    • Olfactory Cells (Bipolar Neuron): Dendrites connected to the olfactory bulb/nerve (CN I).

Olfactory Epithelium Structure

  • Composed of:

    1. Olfactory Neurons

    2. Supporting Cells

    3. Basal Cells

Impairment of Sense of Smell

  • Caused by direct action of viruses along with inflammatory reactions (notably mediated by interleukin-6) affecting olfactory receptors, resulting in impaired olfactory function.

Nasopharynx Structure

  • Connects dorsal portion of the pharynx to the nasal cavity.

  • Separated from oropharynx by the soft palate.

  • Lining: Respiratory epithelium with a muscularis layer of skeletal muscle.

Larynx

  • Connects the nasopharynx with the trachea and serves functions for phonation.

  • Includes a muscularis layer of skeletal muscle supported by hyaline and elastic cartilage.

True Vocal Cords vs. False Vocal Cords

  • True Vocal Cords: Contain skeletal muscle called vocalis muscle and are lined by stratified squamous non-keratinized epithelium.

  • False Vocal Cords: Also known as vestibular folds, lined with respiratory epithelium.

Trachea

  • A flexible tube that connects the larynx and primary bronchi, supported by C-shaped rings of hyaline cartilage.

  • Contains smooth muscle (trachealis muscle) connecting the ends of the cartilage rings.

Bronchial Structure

  • Short, paired tubes bifurcating from the trachea, entering the lungs.

  • Structure similar to the trachea with hyaline cartilage rings and lined with typical respiratory epithelium.

Lung Anatomy

  • Encapsulated with visceral pleura; divided into lobes, with lobular septa dividing lobes into lobules made of loose connective tissue.

  • The intrapulmonary bronchial tree is organized from largest to smallest:

    • Intrapulmonary primary bronchus

    • Secondary bronchus

    • Tertiary bronchus

    • Terminal bronchioles

    • Respiratory bronchioles

    • Alveolar ducts

    • Alveolar sacs

    • Alveoli

Alveoli Overview

  • Alveolar Sacs and Alveoli: Functional units of the lung, involving a simple squamous epithelium lined with two main types of pneumocytes:

    • Type I Pneumocytes: More common, typical squamous cells bulging into the lumen.

    • Type II Pneumocytes: Less frequent, producing surfactant to reduce surface tension and prevent alveoli collapse; can differentiate into Type I if damaged.

Avian Respiratory System

  • Similar to mammals but with structural differences: the trachea is complete and may ossify in certain bird types, and modified air sacs enable efficient air flow for respiration.

  • Syrinx: Functions similarly to the larynx but lacks vocal cords.

Digestive System Overview

  • Composed generally of:

    • Outer serosa (adventitia)

    • Muscularis externa

    • Submucosa

    • Inner mucosa

Oral Cavity Histology

  • Covered by stratified squamous epithelium, with variations in keratinization observed.

Salivary Glands

  • Major glands include the Parotid, Submandibular/Submaxillary, Sublingual, Zygomatic, and Molar glands, secreting saliva into the oral cavity.

Teeth Anatomy

  • Teeth composed of: Crown (enamel) and root (cementum), with internal structures including dentin and pulp cavity.

  • Dentin: Calcified tissue with sensitivity to stimuli and contains tubules transmitting sensation to the dental pulp.

  • Enamel: Remarkably hard structure made up of 96% calcium hydroxyapatite, forming rods crucial for resistance to pressure during mastication.

Esophagus Structure and Function

  • Mucosa is lined with nonkeratinized stratified squamous epithelium, with esophageal glands that provide lubrication.

  • Characterized by weakness of the lower esophageal sphincter leading to conditions such as GERD (Gastroesophageal Reflux Disease).

Stomach Anatomy

  • Comprises four major regions: Cardia, Fundus, Body, and Pylorus, with gastric pits secreting mucus rich in bicarbonate ions to protect the lining.

Small Intestine Structure

  • Divided into the Duodenum, Jejunum, and Ileum, characterized by their respective histological features including villi, crypts, and associated gland types (e.g., Brunner's glands).

Large Intestine

  • Distinct from the small intestine due to the absence of villi and longer crypts, with features like taenia coli in certain species.

Liver Structure

  • Comprised of lobules featuring central veins, hepatic cords, and sinusoids. Portal areas contain the portal vein, hepatic artery, and bile ducts. The hepatic acinus represents a functional unit regarding both blood and bile flow.