### 1. `extract_vegetables(input_text)`
- **Description**: This function extracts the list of vegetables mentioned in the input text.
- **Input**: A sentence describing the vegetables (string).
- **Output**: A list of vegetables mentioned in the input text (list of strings).
- **Example**:
  - **Input**: "I have a lettuce head, a head of broccoli, an onion, a stalk of celery, two carrots, a garlic, and a yam."
  - **Output**: ['lettuce', 'broccoli', 'onion', 'celery', 'carrots', 'garlic', 'yam']

### 2. `count_vegetables(vegetables_list)`
- **Description**: This function counts the total number of vegetables based on the list provided.
- **Input**: A list of vegetables (list of strings).
- **Output**: The total count of vegetables (integer).
- **Example**:
  - **Input**: ['lettuce', 'broccoli', 'onion', 'celery', 'carrots', 'garlic', 'yam']
  - **Output**: 7

### Main Function: `calculate_total_vegetables(input_text)`
- **Description**: This main function calculates the total number of vegetables based on the input text.
- **Input**: A sentence describing the vegetables (string).
- **Output**: The total count of vegetables (integer).
- **Example**:
  - **Input**: "I have a lettuce head, a head of broccoli, an onion, a stalk of celery, two carrots, a garlic, and a yam."
  - **Output**: 7