Human Anatomy - L15

These flashcards cover key vocabulary and concepts related to the digestive system, providing definitions and explanations for better understanding and retention.

What is the pathway of the alimentary canal?

The pathway is: mouth → pharynx → esophagus → stomach → small intestine → large intestine → anus.

What are the main functions of the digestive system's alimentary canal?

Its main functions are digesting food and absorbing nutrients.

Which accessory digestive organs are responsible for the mechanical breakdown of food?

The teeth and tongue are responsible for the mechanical breakdown of food.

Which accessory digestive organs secrete enzymes for starch breakdown?

Salivary glands secrete enzymes for starch breakdown.

Which accessory digestive organs secrete bile and digestive enzymes?

The liver, gallbladder, and pancreas secrete bile and digestive enzymes.

What is the general function of accessory digestive organs?

Accessory digestive organs assist digestion by secretion or mechanical digestion.

What is the role of the peritoneum and mesenteries in the abdominal cavity?

They are responsible for the organization of the abdominal cavity.

What is the peritoneum?

The peritoneum is a serous membrane that lines the abdominal and pelvic cavities.

What are mesenteries and what is their function?

Mesenteries are a double layer of peritoneum that attaches intestines and other abdominal organs to the back of the abdomen.

What is ingestion in the context of digestion?

Ingestion is the process of taking food into the mouth, for example, eating.

What is propulsion in the digestive system, and what are its examples?

Propulsion is the movement of food along the digestive tract, for example, swallowing (voluntary) and peristalsis (involuntary).

What is mechanical digestion, and where does it occur?

Mechanical digestion is the chewing, churning, and segmentation of food. It occurs through the teeth, stomach, and small intestine.

What is chemical digestion, and what is an example of it?

Chemical digestion is the enzymatic breakdown of food molecules. An example is salivary amylase breaking down starch into maltose.

What is absorption in the digestive system, and where primarily does it occur?

Absorption is when nutrients pass from the lumen into the blood or lymph, primarily occurring in the small intestine (via villi).

What is defecation?

Defecation is the elimination of indigestible material from the body, such as feces via the rectum/anus.

Describe peristalsis and where it occurs.

Peristalsis involves 'wave-like' contractions that push food along the digestive tract, especially from the esophagus to the intestines.

Describe segmentation and where it occurs, including its primary function.

Segmentation consists of localized contractions that mix food with enzymes in the small intestine, without forward movement, effectively 'churning the ingredients'.

What is the mucosa layer of the alimentary canal, and what are its functions?

The mucosa is the innermost lining that touches the lumen contents. Its functions include secretion, absorption, and protection.

What are the three sub-layers of the mucosa?

The three sub-layers are the epithelium, lamina propria, and muscularis mucosae.

What type of epithelium lines the mouth, esophagus, and anus, and what is its function?

The mouth, esophagus, and anus are lined with stratified squamous epithelium for protection.

What type of epithelium lines the stomach, and what is its function?

The stomach is lined with simple columnar epithelium for secretion.

What type of epithelium lines the intestines, and what specialized structure does it have for its function?

The intestines are lined with simple columnar epithelium with microvilli, specialized for absorption.

Describe the submucosa layer of the alimentary canal.

The submucosa is dense irregular connective tissue containing blood vessels, lymphatics, and nerves.

What is the muscularis externa responsible for, and what are its two main smooth muscle layers?

The muscularis externa is responsible for movement along the tract, consisting of two smooth muscle layers: the circular muscularis and the longitudinal muscularis.

How do the circular and longitudinal muscularis layers of the muscularis externa contribute to digestion?

The circular muscularis 'squeezes' (runs around the circumference of the organ), and the longitudinal muscularis 'shortens' (runs parallel to the long axis), working together for peristalsis and segmentation.

Which layer of the alimentary canal wall is the outermost, and what is its composition and function?

The serosa (visceral peritoneum) is the outermost layer, consisting of connective tissue and simple squamous epithelium. Its function is to reduce friction against other organs.

When is the outermost layer of the esophagus called "adventitia" instead of serosa?

The outermost layer of the esophagus is called 'adventitia' because it has fibrous connective tissue, not serosa (epithelial cells).

Where is smooth muscle found in the digestive system, and what are the exceptions?

Smooth muscle is found in the walls of most digestive organs (viscera), with the exception of the mouth and upper esophagus, which contain skeletal muscle.

Describe the key characteristics of smooth muscle fibers in the digestive tract.

Smooth muscle fibers are elongated (15-200 ext{ um}), have one nucleus, contain thick and thin myofilaments, and lack striations (no sarcomere).

What are the two types of smooth muscle sheets, and how do their contractions differ?

The two types are circular muscularis, which 'squeezes' around the circumference, and longitudinal muscularis, which 'shortens' parallel to the long axis.

Is smooth muscle contraction voluntary or involuntary?

Smooth muscle contraction is involuntary.

What are the characteristics of smooth muscle contractions regarding speed, duration, energy, and fatigue?

Smooth muscle contractions are slow, sustained, and efficient for gradual food movement. They take 30x longer to contract and relax, have low energy requirements, and are resistant to fatigue.

What are the boundaries of the oral cavity?

The oral cavity is bounded anteriorly by the lips, laterally by the cheeks, medially by the teeth and gums (gingivae), and posteriorly by the fauces (opening to the oropharynx).

What is the anterior opening of the oral cavity called?

The anterior opening is called the oral orifice, which leads into the entrance of the mouth.

What is the posterior opening of the oral cavity called, and what arches define it?

The posterior opening is called the fauces, defined by the palatoglossal arches (palate + tongue) and palatopharyngeal arches (palate + pharynx).

What is the oral vestibule?

The oral vestibule is the space between the lips/cheeks and the teeth/gums.

What is the oral cavity proper?

The oral cavity proper is the inner space enclosed by the teeth/gums and contains the tongue.

What is the labial frenulum?

The labial frenulum connects the lips to the gums, both superiorly and inferiorly.

What are gingivae?

Gingivae are the gums that surround the teeth.

What is the palate, and what are its three regions?

The palate forms the roof of the mouth and has three regions: the hard palate, the soft palate, and the uvula.

Where is the mucosal layer found in the oral cavity, and what is its primary function?

The mucosal layer is found throughout the oral cavity (except gums, hard palate, and dorsal surface of tongue where it's keratinized) and its primary function is protection, being composed of stratified squamous epithelium and lamina propria.

Which areas of the oral cavity are keratinized, and why?

Keratinized areas, such as the gums, hard palate, and dorsal surface of the tongue, are poorly keratinized in the transitional zone of the lips, and are primarily for protection in areas of high friction. Keratinized squamous epithelial cells have no nucleus.

What muscle is responsible for puckering the lips?

The obicularis oris muscle is responsible for puckering the lips.

Describe the characteristics of the transitional zone (pink area) of the lips.

The transitional zone (pink area) of the lips is poorly keratinized, translucent, and lacks sweat or oil glands, causing the lips to dry out easily.

What muscle is found in the cheeks and aids in chewing?

The buccinator muscle is found in the cheeks and aids in chewing.

What type of muscle is the tongue, and what epithelium covers it?

The tongue is a skeletal muscle covered by stratified squamous epithelium.

What are the functions of the tongue?

The tongue grips food, repositions it, and helps form consonants.

What is the lingual frenulum, and what condition can result from a short one?

The lingual frenulum secures the tongue to the floor of the mouth; if short, it can cause 'tongue-tied' condition.

What is the difference between intrinsic and extrinsic tongue muscles?

Intrinsic tongue muscles are within the tongue and alter its shape, while extrinsic tongue muscles originate elsewhere and alter its position.

What nerve innervates the tongue muscles?

The tongue muscles are innervated by Cranial Nerve XII (Hypoglossal nerve).

What is the origin, insertion, and action of the genioglossus muscle?

Origin: internal surface of the mandible near the symphysis (center of chin). Insertion: inferior tongue and hyoid body. Action: protracts the tongue.

What is the origin, insertion, and action of the hyoglossus muscle?

Origin: hyoid bone (body and greater horn). Insertion: inferolateral tongue. Action: depresses the tongue and pulls the sides of the tongue inferiorly.

What is the origin, insertion, and action of the styloglossus muscle?

Origin: styloid process of the temporal bone. Insertion: lateral inferior tongue. Action: retracts and elevates the tongue.

What are tongue papillae, and what are their functions?

Tongue papillae are projections on the tongue surface that give it texture and taste function.

Describe filiform papillae, including their location and whether they contain taste buds.

Filiform papillae are located at the front of the tongue, provide a rough texture, and do NOT contain taste buds.

Describe fungiform papillae, including their location and where their taste buds are found.

Fungiform papillae are located at the front of the tongue and have taste buds on their top surface.

Describe vallate papillae, including their location and where their taste buds are found.

Vallate papillae are located on the sides of the posterior third (1/3) of the tongue and have taste buds on their sides.

What is the sulcus terminalis?

The sulcus terminalis is the border between the mouth and the pharynx.

Which part of the tongue forms the oropharynx, and what lines it?

The posterior third (1/3) of the tongue forms part of the oropharynx and is lined by the lingual tonsil.

What are the two sets of teeth, and how many teeth are in each set?

The two sets are deciduous (baby) teeth, totaling 20 teeth, and permanent (adult) teeth, totaling 32 teeth.

When do deciduous teeth typically appear, and when do permanent teeth typically appear?

Deciduous teeth typically appear around 6 months, and permanent teeth typically appear by the end of adolescence.

What is the adult dental formula, and what do the letters stand for?

The adult dental formula is 2I, 1C, 2P, 3M. I stands for incisors, C for canines, P for pre-molars, and M for molars.

What is the dental formula for children, and what do the letters stand for?

The dental formula for children is 2I, 1C, 2M. I stands for incisors, C for canines, and M for molars (children do not have pre-molars).

What are the main structural components of a tooth?

The main structural components of a tooth are the crown, root, enamel, dentin, pulp cavity, cementum, and periodontal ligament.

Describe the enamel layer of a tooth.

Enamel is the outer layer of a tooth, the hardest substance in the body, and lacks cells and vessels.

Describe the dentin layer of a tooth.

Dentin underlies the enamel; it is bone-like but lacks vessels.

What is the pulp cavity of a tooth?

The pulp cavity is the center of the tooth containing nerves and blood vessels.

What is cementum?

Cementum is calcified connective tissue covering the root of a tooth.

What is the periodontal ligament and what type of joint is it?

The periodontal ligament (peridontium) is connective tissue holding teeth in their sockets, forming a gomphosis joint.

What is a root canal in terms of tooth anatomy?

A root canal is a narrow passageway within the root of a tooth.

What is root canal therapy typically used to treat?

Root canal therapy is typically used to treat cavities that have permanently damaged the tooth's hard surfaces.

What is gingivitis?

Gingivitis is an infection of the gums.

What are the main functions of saliva produced by salivary glands?

Saliva moistens the mouth, dissolves food chemicals for taste, wets food, and aids in the digestion of carbohydrates and fats.

What are minor ("intrinsic") salivary glands, and what is their primary role?

Minor salivary glands are scattered cells within the mucosa, and their primary role is to keep the mouth moist.

What are major ("extrinsic") salivary glands, and when do they secrete saliva?

Major salivary glands secrete saliva only during eating or in anticipation of a meal.

Where are the parotid glands located, and where does their duct open?

Parotid glands are located parallel to the zygomatic arch, and their duct opens at the upper M2 (second molar).

Where are the submandibular glands located?

Submandibular glands are located behind + below jawbone

Where are the sublingual glands located?

Sublingual glands are located under the tongue.

What are the oropharynx and laryngopharynx, and what type of epithelium lines them?

The oropharynx and laryngopharynx are passages for both air and food, and they are lined with stratified squamous epithelium.

What is the function of the suprahyoid muscles, and what nerves innervate them?

Suprahyoid muscles lift the larynx superiorly and anteriorly and depress the mandible. They are innervated by CN V (Trigeminal) and CN VII (Facial).

What is the function of the infrahyoid muscles, and what nerves innervate them?

Infrahyoid muscles return the larynx and hyoid to their original position. They are innervated by spinal nerves.

What are the pharyngeal constrictors, and what is their function?

The pharyngeal constrictors (superior, middle, and inferior) are muscles that contract to squeeze the bolus into the esophagus.

What is a bolus?

A bolus is chewed saliva mixed with food.