Name: digestive glands and enzymes
Uploaded: 2026-08-26T08:20:11.781Z
Duration: 1 min 58 s
Channel: JoVE

K12 Standards

Alabama Course of Study Science

9-12

Human Anatomy and Physiology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

9-12.HA.1.10

Accessory Organs

Accessory digestive organs help the gastrointestinal tract carry out digestion by producing and releasing digestive secretions.The salivary glands in the mouth are the first accessory digestive organs. They release salivary amylase to start carbohydrate digestion by breaking down starch.The remaining accessory digestive organs, such as the liver, gallbladder, and pancreas, are in the abdominal cavity.Their secretions reach the duodenum through ducts, where they help continue digestion.The liver produces bile, and the gallbladder stores and releases it into the duodenum of the small intestine.Bile salts are amphipathic, with hydrophilic and hydrophobic regions. They emulsify large fat globules into smaller droplets.The pancreas secretes digestive enzymes, including lipase and amylase. It also releases inactive protease precursors, such as trypsinogen, chymotrypsinogen, and procarboxypeptidase.Pancreatic lipase hydrolyzes dietary triglycerides into free fatty acids and monoglycerides.Enteropeptidase, released by the small intestine, activates trypsinogen to form trypsin. Once activated, trypsin activates chymotrypsin and carboxypeptidase. Together, these three proteases break proteins into smaller peptides.Pancreatic amylase continues carbohydrate digestion in the small intestine.The pancreas also secretes bicarbonate into the duodenum. This neutralizes acidic chyme and protects the duodenal lining.

accessory organs

Accessory organs are those that participate in the digestion of food but do not come into direct contact with it, unlike the mouth, stomach, or intestine. Accessory organs secrete digestive secretions into the digestive tract to facilitate the breakdown of food.Salivary Glands Salivary glands secrete saliva&#x2014;a complex liquid containing in part water, mucus, and amylase. Amylase is a digestive enzyme that begins breaking down starches and other carbohydrates even before they reach the stomach.Liver, Gallbladder, and Pancreas The liver, gallbladder, and pancreas are the other accessory organs involved in digestion. The liver and gallbladder secrete bile, while the pancreas secretes digestive enzymes into the duodenum through the pancreatic duct. The liver and gallbladder work together to release bile into the duodenum. The liver produces bile, but it is stored in the gallbladder for secretion when needed.Bile is a mixture of water, bile salts, cholesterol, and bilirubin. Bile salts contain hydrophobic areas and hydrophilic areas which allows it to engage with both fats and water. Thus it breaks down large fat globules into smaller ones&#x2014;a process called emulsification. Bilirubin is a waste product that accumulates when the liver breaks hemoglobin from red blood cells. The globin and iron are recycled, while the heme is converted to bilirubin and excreted in the bile. The presence of bilirubin is what gives feces its brown color.Gallstones are bile aggregations that form in the gallbladder or connecting bile ducts. Cholesterol stones are made from mostly from cholesterol in bile. Pigment stones are formed from bilirubin. Most stones form without notice; however, if a stone becomes lodged in the bile duct severe symptoms can emerge such as inflammation of the gallbladder or pancreas, fever, vomiting, and jaundice. A cholecystectomy&#x2014;the removal of the gallbladder&#x2014;is the primary treatment and there are minimal long-term side effects of its removal. Pancreas The pancreas secretes several enzymes. Lipase breaks down the triglycerides into fatty acids and monoglycerides. Trypsin and chymotrypsin catabolize proteins into peptides. Carboxypeptidase then breaks those peptides into individual amino acids. The pancreas also releases amylase to digest any remaining carbohydrates.

Accessory organs are those that participate in the digestion of food but do not come into direct contact with it like the mouth, stomach, or intestine do. ...

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Education

JoVE Core

Biology

Genetics

Nutrition and Digestion

KEY TERMS AND CONCEPTS

digestive glands and enzymes

Digestive glands and accessory organs help break down food even though food does not pass through them. They add enzymes and other fluids to the digestive tract to support digestion.

The salivary glands release saliva, a fluid that contains water, mucus, and amylase. Amylase is a digestive enzyme that starts breaking down starches and other carbohydrates before food reaches the stomach.

The liver, gallbladder, and pancreas also support digestion. They send their secretions into the duodenum, the first part of the small intestine, through channels called the biliary tree. The liver makes bile, and the gallbladder stores it until it is needed.

Bile is made of water, bile salts, cholesterol, and bilirubin. Bile salts have both hydrophobic and hydrophilic regions, so they can interact with fat and water. This lets bile emulsify large fat globules into smaller droplets. Bilirubin is a waste product that forms when the liver breaks down hemoglobin from red blood cells. The globin is recycled, and the heme, which contains iron, leaves the body in bile. Bilirubin also gives feces its brown color.

Gallstones are bile masses that can form in the gallbladder or in nearby bile ducts. Cholesterol stones are made mostly of cholesterol from bile, while pigment stones contain bilirubin. Many stones cause no symptoms, but a stone that blocks a bile duct can lead to serious problems such as gallbladder or pancreas inflammation, fever, vomiting, and jaundice. The main treatment is cholecystectomy, which is the removal of the gallbladder, and it usually has few long-term side effects.

The pancreas releases several enzymes into the small intestine. Lipase breaks smaller fat droplets into fatty acids and triglycerides. Trypsin and chymotrypsin break proteins into peptides, and carboxypeptidase breaks those peptides into individual amino acids. The pancreas also releases amylase to digest any remaining carbohydrates.

Digestive Glands and Enzymes

overview of human digestion

Saliva, Stomach Acid, and Gut Health

The human digestive system is monogastric, which means the stomach has one chamber for digestion. Several other animals also have monogastric digestive systems, including pigs, horses, dogs, and birds. This chapter focuses on the human digestive system. Saliva is a watery fluid released by the salivary glands into the mouth. It is about 99.5% water and also contains electrolytes, mucus, white blood cells, epithelial cells, enzymes, and antimicrobial agents. The enzymes in saliva begin...

anatomy of the intestines

Small and Large Intestine Functions

The small and large intestines complete digestion and absorb nutrients, water, and electrolytes. They are two structurally distinct organs with different shapes and jobs. Together, they move food material from the stomach toward elimination. The small intestine is about 7 meters long and has an inner diameter of only 2.5 cm. Most nutrient absorption happens here, so its inner lining is highly folded and covered with villi, which are finger-like projections. Each villus contains hundreds of...

Digestive glands and accessory organs help break down food even though food does not pass through them. They add enzymes and other fluids to the digestive tract to support digestion. The salivary glands release saliva, a fluid that contains water, mucus, and amylase. Amylase is a digestive enzyme that starts breaking down starches and other carbohydrates before food reaches the stomach. The liver, gallbladder, and pancreas also support digestion. They send their secretions into the duodenum,...

carbohydrate digestion

Carbohydrate Breakdown in the Digestive Tract

Carbohydrate digestion breaks food carbohydrates into saccharides, or sugars, that the body can use for energy. It begins in the mouth during mastication, which means chewing. The masticated carbohydrates then pass through the stomach without being broken down further. Digestion starts again in the duodenum, the first part of the small intestine. There, pancreatic alpha-amylase and brush border enzymes on the microvilli help convert complex carbohydrates into monosaccharides. These simple...

protein digestion

Protein Breakdown and Amino Acid Use

Protein digestion starts in the stomach, where strong acid helps unfold protein structure and expose peptide bonds in polypeptide chains. Digestive enzymes then begin breaking those chains into smaller pieces that can be processed by the body. Pepsin is a protease, which means it is a protein-digesting enzyme. It is made in the stomach and works with chymotrypsin and trypsin, enzymes released in the small intestine. These enzymes cut specific links between amino acids and form shorter...

lipid digestion

Lipases and Bile in Fat Breakdown

Lipases and bile help the body break down lipids, which are large molecules that do not mix well with water. Because most digestive enzymes are water-based, lipids need special steps before the body can use them. Lingual lipase is an enzyme made by acinar cells in the sublingual gland. It is found in saliva, but it has only a small role in the mouth. Its best pH, or acidity level, is 3.5-6.0, so it becomes active after chewed food reaches the acidic stomach. Gastric lipase is another acidic...

neural regulation

Brain and Gut Control of Digestion

Brain and gut control digestion through a cephalic phase and the enteric nervous system. The cephalic phase begins when the brain sees or smells food. It sends impulses through cranial nerves to the salivary glands and stomach so the body is ready to eat. This first response is a conditioned, or learned, reaction to familiar foods. Appetite also changes the response. People may make more saliva and hear more stomach rumbling when they think about apple pie than broccoli. The hypothalamus and...

hormonal regulation

Digestive Hormones and Stomach Control

Digestive hormones control when the stomach makes acid and when food moves into the small intestine. They work with the neuroendocrine system, which links nerve signals and hormone release during digestion. In the stomach, proteins are detected by sensory neurons in the enteric nervous system. This stimulates the pyloric gland to release gastrin. Gastrin then helps trigger histamine release, and together they start hydrochloric acid production. The acid helps break food down into chyme. As the...

key terms and concepts

Learn how the salivary glands, liver, gallbladder, and pancreas add enzymes and bile to digest carbohydrates, fats, and proteins.

Digestive Glands and Enzymes | JoVE K12

JoVE Core series brings biology to life through over 300 concise and easy-to-understand animated video lessons that explain key concepts in biology, plus more than 150 scientist-in-action videos that show actual research experiments conducted in today’s laboratories.

biology

Next Generation Science Standards

High School

Life Science

HS-LS1-2

Florida Department of Education

SC.912.L.14

SC.912.L.14.45

new-york-state-science-learning-standards

New York State Science Learning Standards

Structure and Function

HS-LS1-2.

structural-organization-of-the-human-body-an-overview

Structural Organization of the Human Body: An Overview

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The Endoplasmic Reticulum

Introduction to Cytoskeleton

What are Membranes?

1. Obtain, evaluate, and communicate information to explain how differences in cellular structure (mitochondria, cytoskeletal structure, endoplasmic reticulum, cell membrane) lead to differences in the function and organization of the four tissue types (epithelial, connective, muscular, and nervous).

9-12.HA.1.1

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Accessory Structures of the Skin: Sweat Glands

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Accessory Structures of the Skin: Hair and Hair Follicles

Hair and hair follicles are integral components of the integumentary system. Hair is a filamentous structure composed mainly of a protein called keratin. ...

Accessory Structures of the Skin: Nails

Nails are one of the important accessory structures of the skin. They are hard, protective structures that cover the dorsal surface of the distal ...

2. Obtain, evaluate, and communicate information to describe how the structures of the integumentary system and its accessory organs contribute to its function. Examples: how the layers of the skin contribute to homeostasis, the role of glands in thermoregulation and in hydration of skin and mucous membranes, the protective functions of hair and nails

9-12.HA.1.2

Thermoregulation

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Defense Mechanism Against Infection

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...

a. Construct an explanation of the relationships between the integumentary system and other organ systems, including the body's mechanisms for maintaining homeostasis. Examples: Explain how changes in vessel diameter and evaporation of water over the skin contribute to thermoregulation (cardiovascular). Explain how sweat is used to excrete nitrogenous waste from the blood (cardiovascular). Explain how the skin and mucous membranes create a barrier against infection (immune system).

9-12.HA.1.2.a

Introduction to the Skeletal System

The skeletal system is the central framework of the body, consisting of different connective tissues: bones, cartilage, tendons, and ligaments.
Components ...

Classification of Bones

The bones of the human skeletal system are of varied shapes, sizes, and functions. They can be classified based on their shape and function into four ...

Overview of the Axial Skeleton

The skeleton is subdivided into two major divisions&#8212;the axial skeleton and the appendicular skeleton. The axial skeleton forms the vertical, central ...

Introduction to Joints

The adult human body usually has 206 bones, and except for the hyoid bone in the neck, each bone is connected to at least one other bone. Joints are the ...

Joints

Joints, also called articulations or articular surfaces, are points at which ligaments or other tissues connect adjacent bones. Joints permit movement and ...

3. Develop and use a model to illustrate how the structures of the skeletal system contribute to its function. Examples: Create a diagram or 3D model to illustrate bone shape, joint types, and bones in the appendicular and axial skeletons. Use models to illustrate the role of the skeletal system in movements around joints, support of a body structure, and protection of soft tissues.

9-12.HA.1.3

bone-formation-by-endochondral-ossification

Bone Formation by Endochondral Ossification

Bone formation, or ossification, begins around the sixth to seventh week of embryonic development. Most bones develop from a cartilaginous template ...

bone-formation-by-intramembranous-ossification

Bone Formation by Intramembranous Ossification

Intramembranous ossification is one of the two processes involved in the development of bones within an embryo. The flat bones of the face, most of the ...

Bone Remodeling and Repair

a. Obtain, evaluate, and communicate information describing the growth and development of the skeletal system.

9-12.HA.1.3.a

The Functions of the Skeletal System

The most apparent functions of the skeletal system are support, protection, and movement. However, bone tissue also performs several other critical ...

Skeleton and Calcium Homeostasis

Calcium is not only the most abundant mineral in bone but also the most abundant mineral in the human body. Calcium ions are needed for bone ...

The Bone Matrix

Bone contains a relatively small number of cells entrenched in a matrix of collagen fibers that provide an adherent surface for inorganic salt ...

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Hematopoiesis, or hemopoiesis, is the production of the formed elements in blood from common progenitors, called hematopoietic stem cells, or HSCs.
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b. Construct an explanation of the relationships between the skeletal system and other organ systems, including the body's mechanisms for maintaining homeostasis. Examples: Explain the role of spongy bone in hematopoiesis (cardiovascular system) and leukopoiesis (immune system). Explain how the storage of minerals in bone contributes to homeostasis.

9-12.HA.1.3.b

The Muscular System

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Naming Skeletal Muscles

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Often, muscle names indicate their location. For ...

Muscle Coordination and Action

The skeletal muscles can coordinate, oppose, or assist each other to facilitate voluntary body movements.
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Fascicle Arrangement in Skeletal Muscles

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4. Develop and build a three-dimensional model to illustrate the structures of the muscular system, including muscle locations, origins, and insertions, and explain their roles in movement and support. Example: Design and build a model of a lever to illustrate the relationship between bones and muscles and explain their roles in body movement and support.

9-12.HA.1.4

Microscopic Anatomy of Skeletal Muscles

Each skeletal muscle is composed of multiple bundles of elongated multinucleated muscle cells or muscle fibers.
These cells are enclosed by a plasma ...

The Sarcomere

A sarcomere is mainly made up of two types of filaments&#8212; thin filaments containing actin, troponin, and tropomyosin and thick filaments containing ...

excitation-contraction-coupling-in-skeletal-muscles

Excitation-Contraction Coupling in Skeletal Muscles

Excitation-contraction coupling is a series of events that occur between generating an action potential and initiating a muscle contraction. It occurs at ...

Relaxation of Skeletal Muscles

The period of muscle contraction primarily influences the duration of stimulation at the neuromuscular junction (NMJ), the presence of free calcium ions ...

a. Model the cellular physiology of skeletal muscle, including how the cell functions in muscle contraction and relaxation. Example: Use straws and paper to create a model of a sarcomere to illustrate how the fibers move during contraction and relaxation.

9-12.HA.1.4.a

Muscle Recovery and Fatigue

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Muscle Stimulation Frequency

Depending on the demand, motor neurons control the strength of a muscle&#39;s contraction by altering the frequency of action potentials delivered to the ...

b. Obtain, evaluate, and communicate information to explain muscle fatigue and tone in terms of muscle cell physiology.

9-12.HA.1.4.b

Organization of the Nervous System

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Functional Divisions of the Nervous System

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Anatomy of the Brain: Major Regions

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Peripheral Nervous System: Ganglia and Nerves

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5. Obtain, evaluate, and communicate information explaining the relationship between the structures and functions of the central nervous system and the peripheral nervous system.

9-12.HA.1.5

Action Potential

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Propagation of Action Potentials

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Action Potential: Phases of Stimulation

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Voltage-gated Ion Channels

a. Use a model to illustrate the role of action potentials in neural transmission. Clarification: Discussions of sodium-potassium pumps and ion channels are not required.

9-12.HA.1.5.a

Somatic Spinal Reflexes

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b. Construct an explanation of the role of reflex arcs, the central nervous system, and special senses in the response to stimuli to maintain homeostasis and guide behavior. Example: smelling a strong odor initiating a sneeze response using a reflex arc; pupil diameter changing in relation to the amount of light entering the eye Clarification: Discussion of the anatomy and physiology of the sensory organs is not required.

9-12.HA.1.5.b

Neurotransmitters

Neurotransmitters play a crucial role in the communication between neurons in the autonomic nervous system. Neurons in the autonomic nervous system can be ...

Chemical Synapses

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The Synapse

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c. Construct an explanation of the role of neurotransmitters in the functions and behavior of the nervous system. Clarification: Discussion of classes of neurotransmitters is not required.

9-12.HA.1.5.c

Functional Brain Systems: Limbic System

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d. Obtain, evaluate, and summarize scientific findings regarding the biological origin of emotions and memories in distinct regions of the brain. Examples: the role of the frontal lobe in emotional regulation, the regulation of fear response by the amygdala

9-12.HA.1.5.d

Digestive Glands and Enzymes

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