(FIRST RECITATION) ANATOMY OF DIGESTIVE SYSTEM

Main function of digestive system

• digestion

• Absorption of nutrients

• Elimination of feces

Main segments of digestive system

• mouth

• Pharinx

• Esophagus

• Stomach

• Intestine

• Small intestine (duo, jeju, ileum)

• Large intestine

• Anus

Digestive glands

• Salivary gland

• Liver

• Pancreas

Accessory digestive structures

• Teeth

• Tongue

• Cheeks

• Lips

Oropharynx (pharyngeal apertures)

Open to oral cavity

Nasopharynx (pharyngeal apertures)

Opens to nasal cavity

Laryngopharynx

Opens to larynx and esophagus

Pharyngeal proper

• junction of apertures

• Shared by digestive and respiratory track

Esophagus description

• Long tubular tube

• Transports bolus from pharynx to stomach

• pH is slightly acidic to slightly alkaline

Segments of esophagus

• cervical

• Thoracic

• Abdominal

Layers of esophagus

• tunica mucosa

• Tunica submucosa

• Tunica muscularis

• Tunica adventitia

Stomach (description)

• muscular sac

• Temporary store chyme

• Strongly acidic because of hydrochloric acid

Parts of stomach

• cardia

• Fundus

• Body

• Pylorus

Sphincters of stomach

• cardiac sphincter (esophagus of stomach)

• Pyloric sphincter (stomach to small intestine)

Layers of stomach

• tunica mucosa

• Tunica submucosa

• Tunica muscularis

• Tunica serosa

Gastric gland cells of stomach

• parietal cells (secretes hydrochloric acidH

• Chief cells (secretes pepsinogen)

Surfaces of stomach

• parietal surface

• Visceral surface

Curvatures of stomach

• Greater curvature

• Lesser curvature

Small intestine (description)

• long tubular organ

• Main site of nutrient absorption

• Called small because of its smaller diameter

Fixed parts of small intestine

Duodenum

Movable or mesenteric part of small intestine

Jejunum

Segments of small intestine

• duodenum

• Jejunum

• Illeum

Duodenum

• fixed segment

• Receives bile and pancreatic secretions

Jejunum

• longest part

• Most absorptive part

• Movable part

Ileum

• terminal part

• Has Peyer’s patches

• Important for lymphoid defense

Large intestine (description)

• shorter but wider than small intestine

• Responsible for water reabsorption

• Responsible for electrolyte reabsorption

• Forms feces

Segments of large intestine

• cecum

• Colon

• Rectum

Cecum

Site of fermentation

Colon

Water and electrolyte reabsorption

Rectum

Temporary fecal storage before defacation

Anus (description)

Terminal segment of alimentary canal

Anal sphincters

• internal anal sphincter

• external anal sphincter

Major Salivary glands and secretions

• parotid

• Submandibular gland

• Sublingual gland

• Zygomatic gland

Notes in digs about salivary glands and secretions

• zygomatic gland is the fourth major salivary gland

• Located near the orbit

Types of secretion

• serous (water)

• Mucous (thick)

• Mixed (combination of both)

Liver (description)

• largest gland

• Nutritional guardian

• Located against the diaphragm

• Produce bile

• Bile is stored in the gall bladder

Structural unit of liver

• hepatic lobule

• Hexagonal shape

Lobes of liver

• left and right lobe

• Median or quadrate lobe

• Caudate lobe

Caudate lobe

Lobe of liver that has papillary process

Surfaces of liver

• Parietal surface (convex)

• Visceral surface (flat)

Borders of liver

• dorsal border

• Ventral border

• Lateral border

Location of pancreas

In the duodenal loop

Functional portions of pancreas

• exocrine portion

• Endocrine portion

Exocrine portion of pancreas

• made of pancreatic acinar cells

• Secretes pancreatic juice

Exocrine secretions

• Amylase (digests carbs)

• Lipase (digest fats)

• Trypsinogen (inactive enzyme for protein digestion)

• Chymotrypsinogen (inactive enzyme for protein digestion)

Amylase (pancreas)

Digests carbs

Lipase (pancreas)

Digests fats

Trypsinogen (pancreas)

Inactive enzyme for protein digestion

Chymotrypsinogen (pancreas)

Inactive enzyme for protein

Endocrine portion of pancreas

Made of islets if langerhans

Endocrine secretions of pancreas

• alpha cells

• Beta cells

Alpha cells

• secrete glucagon

• Increases blood sugar

Beta cells

• secretes insulin

• Decreases blood sugar

Teeth (functions)

• Cutting

• Tearing

• Grinding

• Chewing

Types of teeth

• incisors

• Canines

• Premolars

• Molars

Teeth note: Deciduous teeth

Lack molars

Teeth surfaces

• occlusal surface

• Labial surface

• Lingual surface

Layers of teeth

• enamel

• Dentine

• Cementum

• Pulp cavity

teeth regions

• crown

• Neck

• Root

Carnassial teeth in dogs (for sheering)

• cutting teeth

• Last upper premolar

• First lower molar

Tongue (description)

• supported by mylohyoideus muscle

• Helps in food manipulation, taste, and swallowing

Parts of tongue

• root

• Body

• Apex

Lingual papillae

• filiform - bristile-like

• Fungiform - mushroom-shaped

• Folate - leaf type

• Vallate - V shaped

Hard palate

• bony roof of the mouth

• Bounded by alveolar arches

Bony framework of palate

• premaxillae

• Maxillae

• Palatine bones

Soft palate

• caudal continuation of hard palate

• Has base and free border

Surfaces of palate

• oral surface

• Aboral surface

Pillars of palate

• anterior palate (related to tongue)

• Posterior pillar (related to esophagus or pharyngeal region)

Main segments of respiratory system

• nasal cavity

• Pharynx

• Larynx

• Trachea

• Bronchi

• Lungs

Nasal cavity

• entry point for air

• Filters, warms, and humidifies air

Pharynx

Shared passageway for air and food

Larynx

• voice box

• Connects pharynx and trachea

• Protects airways during swallowing

Trachea

• wind pipe

• Supported by cartilaginous rings

• Carries air to bronchi

Bronchi

• branches from trachea at the carina

• Carry air into lungs

Lungs

Main organs for gas exchange

Dorsal (nasal cavity boundery)

Nasal bone

Lateral (nasal cavity boundery)

Premaxilla and maxilla

Ventral (nasal cavity boundery)

Palatine bone or hard palate

Rostral (nasal cavity boundery)

External nares

Caudal (nasal cavity boundery)

Choanae (used to breathe even if mouth is closed)

Unpaired Laryngeal cartilages

• epiglottic cartilage

• Thryroid cartilage

• Cricoid cartilage

Paired Laryngeal cartilage

• arytenoid cartilages

• Corniculate cartilages

• Cuneiform cartilages

Layers from outer to inner of trachea

1. Fascia propria

2. Cartilage

3. Elastic Layer

4. Muscle

5. Mucosa

Bronchial tree (branches)

• primary bronchi

• Secondary bronchi

• Tertiary bronchi

• Bronchioles

• Alveoli

Borders or regions of lungs

• Dorsal border

• ventral border

Pointed and wide parts of lungs

• apex (pointed portion)

• Base (broad bottom portion)

Pleura (serous membranes of lungs)

• Visceral pleura (covers the lungs)

• Parietal pleura (lines of thoracic cavity)

Visceral pleura

Covers the lungs

Parietal pleura

Lines the thoracic cavity

Lines of pleural reflection

• vertebral line

• Sternal line

• Diaphragmatic line

Mediastinum (description)

• central portion of the thoracic cavity

• Located between right and left cavities

• Contains the heart, vessel, trachea, esophagus, nerves, lymphatic structures

Regions of mediastinum

• pre-cardial mediastrinum

• Cardial mediastrinun

• Post-cardial mediastrinum

Pre-cardial mediastrinum

• cranial to heart

• Contains trachea, esophagus, vessel, nerves, thymus, and lymph nodes

Cardial mediastinum

• Region of the heart

• Contain heart, pericardium, great vessels, and main bronchi

post-cardial mediastinum

• caudal to heart

• Contains esophagus, descending aorta, caudal vena cava, thoracic duct, azygos vein, nerves, and lymph nodes