Digestive System Functions Lesson Plan (TEKS 7.13A): A Complete 5E Lesson for the Mouth-to-Intestine Path, Enzymes, and Nutrient Absorption

Chris Kesler · 10 min read

The first time I taught the digestive system to 7th graders, I asked the class what happens to a slice of pizza after you swallow it. The answers were creative. "It goes to the stomach." "It dissolves." "It becomes poop." One kid said the stomach "just kills it." Almost nobody mentioned the small intestine. Nobody mentioned enzymes. The space between mouth and toilet was a complete black box to them.

What flipped it was the day I unrolled a 20-foot string across the front of the room and told them that was how long their small intestine would be if you stretched it out. The room went silent. I let it hang there for a second, then walked them through the journey: chew it in the mouth, swallow it through the esophagus, churn and acid-soak it in the stomach, then send the soupy mess into 20 feet of intestine where the actual nutrient absorption happens. Suddenly the stomach wasn't "the place where food goes." It was step three of a much longer trip. Once kids saw the whole tube, the vocabulary clicked.

That's the core idea behind this 5E lesson for TEKS 7.13A. Students don't just memorize the names of organs. They trace food through the entire tract, model mechanical and chemical digestion with their hands, and walk away understanding the digestive system as one long, coordinated path from mouth to large intestine.

⏱ About 10 class periods 📓 7th Grade Life Science 🍎 TEKS 7.13A 🎯 Differentiated for D + M 💻 Print or Digital

Inside the Digestive System Functions 5E Lesson

The 5E instructional model walks students through five phases: Engage, Explore, Explain, Elaborate, and Evaluate. It flips the traditional lecture-first sequence on its head. Students explore a concept hands-on before you ever explain it, which means by the time you do explain it, they have something to hook the vocabulary onto.

I switched to the 5E model years ago and stopped going back. Kids retain more, ask better questions, and stop staring at me waiting to be told the answer. The Digestive System Functions 5E Lesson is built on this framework from start to finish. Here's how it plays out across the five phases.

🎯 Engage

I CAN statement and key vocabulary for the digestive system functions lesson

Day one is a teacher-led hands-on exploration. Each small group gets a labeled diagram of the human body and a set of organ cards (mouth, esophagus, stomach, small intestine, large intestine, rectum, plus accessory organ cards for liver, gallbladder, and pancreas). Following the teacher directions, they place the cards in the correct order along the digestive tract and sort the accessory organs off to the side. The 20-foot string demonstration is built in as a hook.

By the end of the period, kids have the digestive tract diagrammed, an annotated student sheet that distinguishes the main tract from accessory organs, and they can explain in their own words why digestion is one long path, not a single event in the stomach. Nobody has heard a vocabulary lecture yet. That's the point. They walk into the rest of the unit with a working model of how food actually moves, not a memorized list of organs.

What's included in the Engage:

Teacher directions for the digestive tract ordering activity
Printable student observation sheet
Answer key for the discussion questions
Four learning objective slides (standard verbatim, "Describe" verb highlighted, "I CAN...", and "WE WILL...")
An illustrated Body Systems Word Wall in English and Spanish covering the full unit vocabulary

🔬 Explore

📷 Explore image 1 — wide shot of Station Lab in action

The Digestive System Functions Station Lab is the heart of the Explore phase. Students rotate through 8 stations (plus a 9th challenge station for early finishers) over one class period. The Station Lab is split into four input stations (where kids take in new information) and four output stations (where they show what they learned).

The four input stations:

🎬 Watch It! — Students watch a short video on the structure and function of the digestive system and answer guided questions about the path of food, accessory organs, and enzymes.
📖 Read It! — A one-page reading passage at two differentiated levels, with a Spanish version included.
🔬 Explore It! — Students model mechanical and chemical digestion using a cracker (chew it, then mix it with water in a baggie, then add a few drops of weak acid like lemon juice) and observe how the cracker changes at each step.
💻 Research It! — Reference cards on the path of food through the digestive tract, the difference between mechanical and chemical digestion, the role of villi in the small intestine, and the four main accessory organs.

The four output stations:

📋 Organize It! — A card sort where students place digestive events (chewing, stomach acid mixing, bile breaking up fat, water absorption) under "mechanical" or "chemical" digestion and justify each choice.
🎨 Illustrate It! — Students draw a labeled diagram of the digestive tract from mouth to rectum and label which organs are part of the tract versus which are accessory organs.
✍️ Write It! — Three open-ended questions in complete sentences (this is where you see who really understands the small intestine and absorption).
📝 Assess It! — A short formative check with multiple choice and a fill-in-the-blank vocabulary paragraph.

📷 Explore image 2 — close-up of featured station (Explore It! or Organize It!)

Print and digital versions are both included. If you want the full breakdown of what happens at every single station, what students produce, and how to set it up, that's in our dedicated Station Lab post.

→ Read the full Digestive System Functions Station Lab walkthrough 8 stations, materials list, teacher tips

The Station Lab is included in the full 5E lesson. You don't need to buy it separately if you're getting the whole unit.

📚 Explain

📷 Explain image 1 — Presentation slide screenshot

Here's the real payoff of doing the Engage and Explore before the Explain: by the time kids hit this phase, they've already traced food through the tract and watched a cracker break down chemically in a baggie. They have a working understanding before you ever start naming things. The discussions get deeper, the questions get sharper, and you spend less time defining and more time pushing their thinking.

The Digestive System Functions Presentation walks 7th graders through the full scope of TEKS 7.13A for this system, one concept at a time. The deck opens with the big function of the digestive system: it turns food into nutrients the body can actually use for energy, growth, and repair. Then it introduces the difference between the two kinds of digestion that happen along the way. Mechanical digestion changes the shape and size of food without changing what it is. Chewing is mechanical. The churning of the stomach is mechanical. Chemical digestion uses enzymes and acid to actually break the chemical bonds in food and turn it into smaller molecules the body can absorb. Both kinds of digestion happen at the same time, and both have to work for food to actually become nutrients.

📷 Explain image (middle) — Presentation slide screenshot (classification hierarchy, Essential Question, or category comparison)

From there the deck walks the path of food step by step. The journey starts in the mouth, where teeth chew (mechanical) and saliva mixes in (chemical). Saliva contains an enzyme called amylase that begins breaking down starches. From the mouth, food moves into the esophagus, a 10-inch muscular tube that uses waves of muscle contractions to push food down to the stomach. The stomach is a J-shaped muscular organ that churns food (mechanical) and bathes it in hydrochloric acid and digestive enzymes (chemical). The acid also kills harmful bacteria, which is one reason why old food often makes you feel sick. From the stomach, the soupy mixture moves into the small intestine, which is where the real action happens. The small intestine is about 20 feet long, and its walls are lined with tiny finger-like projections called villi that massively increase the surface area for absorption. Nutrients pass through the villi into the bloodstream and get carried throughout the body. Leftover undigested material moves into the large intestine, where water is reabsorbed and waste is compacted, then finally exits through the rectum.

Then the lesson tackles the accessory organs, which is the part that trips up almost every 7th grader. The accessory organs do crucial digestion work, but food never actually passes through them. The liver produces bile, a yellow-green liquid that breaks up fats into smaller droplets so enzymes can work on them. The gallbladder stores bile until it's needed and squirts it into the small intestine when fat shows up. The pancreas produces a cocktail of digestive enzymes that finish breaking down carbohydrates, proteins, and fats in the small intestine. (The pancreas also makes insulin for the endocrine system, which is a great cross-system connection to highlight.) The deck includes a built-in matching activity where students drag accessory organs to their functions. Once kids see that the liver, gallbladder, and pancreas are essential helpers but not part of the tube itself, the system clicks.

📷 Explain image 2 — Presentation slide screenshot

The deck closes by tying the digestive system back to the other body systems it works with. The digestive system needs the circulatory system to carry absorbed nutrients to every cell. It needs the muscular system for chewing, swallowing, and peristalsis (the wave of muscle contractions that pushes food through the tract). It works with the endocrine system through the pancreas and through hormones that control hunger. It hands off undigested waste to the urinary and immune systems for filtering. That kind of cross-system thinking is exactly what TEKS 7.13A is asking for.

What makes the Digestive System Functions Presentation different from a typical body-systems slideshow is that kids are doing something on almost every slide. It's not a lecture deck. It's a participation deck. "Your answer:" prompts appear on most slides, Brain Breaks reset attention every few slides (one has kids talk about "down the wrong pipe" and the role of the epiglottis), and Quick Action INB tasks (mechanical vs. chemical sorting, organ labeling, accessory organ matching) show up throughout. Think About It prompts push deeper into bigger ideas like designing a model of food's journey and analyzing how celiac disease damages villi in the small intestine. The deck closes with a Check for Understanding tied back to the Essential Questions: What is the main function of the digestive system? and How does it interact with the other body systems?

The Explain materials in this product include:

An editable Presentation at two differentiated levels (Dependent and Modified), works in PowerPoint or Google Slides
A guided fill-in-the-blank student notes handout that mirrors the Presentation, with answer key
A Paper Interactive Notebook (English and Spanish) students cut, fold, and glue into their notebooks
A Digital Interactive Notebook at both levels with answer keys, for 1:1 classrooms or Google Classroom

The Explain runs across two class periods. The built-in Think About It prompts are where the real discussion happens, so let those breathe.

🛠️ Elaborate

Student choice project options and rubric for the digestive system functions lesson

The Elaborate phase is where students stretch what they learned about the digestive system and put it into a project of their choosing. In this 7th grade life science lesson, that's a Student Choice Project board with six different project options plus a "design your own" pathway.

Students might build a 3-D model of the digestive tract showing the path of food from mouth to rectum, design an infographic comparing mechanical and chemical digestion with real-world examples, write a short story from the point of view of a bite of pizza traveling through the tract, or record a video walking through the role of each accessory organ. There are options for kids who love to write, kids who love to draw, kids who love to build, and kids who love to perform. Whatever the project, the point is the same: students apply the path of food, mechanical and chemical digestion, and accessory organ functions to a real-world artifact instead of a worksheet.

Choice is the whole point. By letting students pick how they show their thinking, you get more authentic work for TEKS 7.13A and you actually get to see what they understand about the digestive system.

The rubric (the part teachers actually want)

Every project, no matter which option a student picks, is graded on the same rubric. Five categories at 20 points each:

Vocabulary (20 pts) — At least four words from the lesson are used in context.
Concepts (20 pts) — At least two key concepts from the lesson are referenced.
Presentation (20 pts) — The project grabs attention and is well-organized.
Clarity (20 pts) — Easy to understand. Free of typos.
Accuracy (20 pts) — Drawings and models are accurate. The science is right.

The rubric uses a minus / check / plus shorthand on every row so you can grade a stack of projects quickly without re-reading every criterion.

Two differentiated versions in one file

The standard version is for students ready for independent application of digestive system ideas. The Reinforcement version is for students who need additional vocabulary or concept support. Three of the six options are swapped for projects with a tighter vocabulary tie-in, and "design your own" is replaced with "collaborate with the teacher" so kids aren't pitching cold.

✅ Evaluate

The Evaluate phase wraps the unit with a formal assessment. It's not all bubble-in. Several questions show students labeled diagrams of the digestive tract and ask them to identify the organ, the type of digestion, and the function of the accessory organs.

The full assessment has 12 questions across five formats:

Multiple choice (4 questions) covering the order of organs in the digestive tract, the difference between mechanical and chemical digestion, the role of the small intestine in absorption, and the accessory organs
Hotspot / visual (2 questions) where students click the small intestine on a body diagram and identify the part of the tract where most nutrient absorption happens
Multiselect (2 questions) where students pick all of the accessory organs of digestion, and all of the events that count as chemical digestion
Short answer (2 questions) on how mechanical and chemical digestion work together and on the role of villi in nutrient absorption
Multipart scenario (2 questions) with a real-world example (a student who just ate a cheeseburger) where students trace the food through the tract, identify where mechanical and chemical digestion occur, and explain how the liver and pancreas help

A modified version is included for students who need additional support. Fewer multiple-choice distractors and sentence-starter scaffolds on the short-answer items.

If you've taught all five phases, this assessment shouldn't surprise anyone. It's a chance for kids to show you they get it.

How everything fits together

If you want the whole experience (Engage hook, the Station Lab as the Explore, the Explain day with Presentation and interactive notebook, the Student Choice Elaborate, and the Evaluate assessment all in one download), that's the Digestive System Functions Complete 5E Science Lesson.

If you only need the one-day hands-on activity, the Station Lab works as a standalone. Most teachers buy the full 5E because the Station Lab works harder when it's bookended by a strong Engage and a follow-up Explain. But both are honest options.

Two options

Digestive System Functions Complete 5E Lesson cover

Full 5E Lesson — ~10 class periods $13.20 Get the 5E Lesson

Digestive System Functions Station Lab cover

Just the Station Lab — 1–2 class periods $7.20 Get the Station Lab

What you need to teach Digestive System Functions (TEKS 7.13A)

Materials beyond what's in the download:

Printed digestive organ cards and tract diagrams for the Engage activity (templates included)
Saltine crackers, plastic baggies, water, and lemon juice (or weak vinegar) for the Explore It! digestion modeling station
A 20-foot length of string or yarn for the small intestine demonstration
Pencils, colored pencils or markers, and printed student pages
A device with internet for the Watch It! station and the slide deck

Standard covered: Texas TEKS 7.13A — Describe the function and interactions of major body systems in organisms, including the skeletal, muscular, nervous, respiratory, integumentary, circulatory, endocrine, digestive, immune, and urinary systems. See the full standard breakdown →

Grade level: 7th grade science

Time: About 10 class periods of 45 minutes each, done with fidelity. The product also ships with a compressed sample unit plan if you need to move faster.

Common misconceptions this lesson clears up

"All digestion happens in the stomach"
The stomach gets all the credit because it's the part of digestion you actually feel (growling, fullness, the occasional ache). But the stomach is just one stop on a long journey. Digestion starts in the mouth, where chewing breaks food into smaller pieces and saliva starts breaking down starches with the enzyme amylase. It continues in the stomach, where acid and enzymes do more chemical work. But the heavy lifting actually happens in the small intestine, which is about 20 feet long and is where most chemical digestion finishes and where almost all nutrient absorption takes place. The stomach is more like the mixing bowl. The small intestine is where the meal actually feeds the body.
"Food goes directly from the stomach into the bloodstream"
The stomach is not where food enters the blood. Food enters the bloodstream through the walls of the small intestine. The small intestine is lined with millions of tiny finger-like projections called villi. Villi massively increase the surface area of the intestine wall, which means more space for nutrients to pass through and into the blood vessels that wrap around the outside. From there, the bloodstream carries the nutrients all over the body. The stomach is where food gets broken down enough to even be absorbed. The small intestine is where the actual handoff to the bloodstream happens. Two different jobs, two different organs.
"The liver is part of the digestive tract that food passes through"
The liver is essential to digestion, but food never actually passes through it. The liver is an accessory organ. Its job is to produce bile, a yellow-green liquid that breaks up fats into smaller droplets in the small intestine so enzymes can finish digesting them. The bile flows from the liver to the gallbladder, where it's stored, and then gets released into the small intestine when fat shows up. The food itself stays in the tract (mouth, esophagus, stomach, small intestine, large intestine, rectum). The liver, gallbladder, and pancreas all dump their helpful juices into the tract from the sides. Same digestive system, different roles.
"Fiber gets fully digested like the rest of your food"
Fiber is one of the few things you eat that your body cannot fully digest, and that's the whole point of fiber. Your digestive enzymes can't break down the chemical bonds in fiber, so it travels through the small intestine without getting absorbed. By the time it reaches the large intestine, it's still mostly intact. There, fiber plays two important jobs: it gives the gut bacteria something to feed on, and it adds bulk to the waste that's about to exit the body. That bulk is what helps move everything along smoothly. So fiber isn't fuel for your cells. It's fuel for your gut bacteria and a structural helper for the system itself. It's one of the few things on your plate that's useful precisely because it doesn't get fully digested.

What's included in the Digestive System Functions 5E Lesson download

📷 Inside-the-product — add screenshot of Read It passage or sample answer sheet

When you buy the Digestive System Functions Complete 5E Lesson, you get a single download with the whole unit:

✅ Engage materials — teacher directions, student observation sheet, answer key, four learning objective slides, illustrated Body Systems Word Wall (English + Spanish)
✅ The full Station Lab — 8 stations + 1 challenge, print and digital, two reading levels, Spanish Read It!
✅ Explain materials — editable Presentation at two differentiated levels (with built-in Brain Breaks, Quick Action INB tasks, and Think About It prompts), guided fill-in-the-blank student notes handout with answer key, Paper Interactive Notebook (English + Spanish), Digital Interactive Notebook at two levels with answer keys
✅ Elaborate (Student Choice Projects) — 6 project options + design-your-own, plus a Reinforcement version with vocabulary-focused alternatives, 5-category rubric included
✅ Summative assessment — full 12-question version and modified version with sentence-starter scaffolds, both with answer keys
✅ Sample unit plan — day-by-day pacing guide

A couple of real-talk tips from running this lesson

1. Unroll the 20-foot string on Day 1.

Before any vocabulary at all, unspool 20 feet of string across the room and tell the class "this is how long your small intestine is." The reaction is always the same: silence, then arguments about whether it could possibly fit inside their body. That single demonstration sets up the whole "why the small intestine matters" conversation. Free hook.

2. Use the cracker baggie for chemical digestion.

The cracker-in-a-baggie activity is the cleanest way to show kids what "chemical digestion" actually means. Chew a cracker (mechanical), put a fresh cracker plus water in a baggie and squeeze (mechanical plus chemical from saliva amylase), then add a few drops of weak acid like lemon juice to simulate stomach acid. The cracker turns into a sludgy mush. They see the chemistry happening without any hand-waving.

3. Separate the tract from the accessory organs early.

The biggest source of confusion in the unit is whether the liver, gallbladder, and pancreas are "part of digestion." Yes, they're essential. No, food doesn't pass through them. Make a clean two-column chart on Day 1 (Tract / Accessory Organs) and refer back to it every day. By the assessment, kids won't put the liver on the food path.

Get the Digestive System Functions 5E Lesson

Buy the full Digestive System Functions 5E Lesson — $13.20

Or if you only need the one-day hands-on Station Lab:

Buy the Digestive System Functions Station Lab — $7.20

(The Station Lab is included in the full 5E Lesson)

Frequently asked questions

Does this cover all of TEKS 7.13A?

For the digestive system, yes. The full standard asks students to describe the function and interactions of all 10 major body systems. This lesson covers the digestive system in depth, including the path of food, mechanical and chemical digestion, accessory organs, and how it interacts with the circulatory, endocrine, muscular, and urinary systems. We have nine more 5E lessons for the other body systems under the same standard.

What do my students need to know before this lesson?

A basic understanding of cells, tissues, and organs from earlier grade-level standards. If your kids can describe what an organ is and the difference between a cell and a tissue, they're ready.

How long does it take to teach?

Done with fidelity, about 10 class periods of 45 minutes each: one day for the Engage, two days for the Station Lab, two days for the Presentation and Interactive Notebook, three days for the Student Choice Project, and one to two days for review and the assessment. A compressed sample plan is included in the file if you need to move faster.

Do I need special supplies?

Just saltine crackers, plastic baggies, water, and lemon juice (or weak vinegar) for the Explore It! station, plus a 20-foot length of string for the small intestine demo. Most teachers already have what they need.

Does this work for digital classrooms?

Yes. Every component has a digital version. The Station Lab is fully digital-ready (Google Slides), the Presentation works in Google Slides, and the Student Choice Projects can be submitted as videos, slide decks, or written work.

Is this 5E lesson aligned to NGSS too?

It aligns with MS-LS1-3 (using arguments supported by evidence for how the body is a system of interacting subsystems composed of groups of cells). Built TEKS-first, but the standards overlap.